Recoll user manual

Author:Jean-Francois Dockes

Introduction

This document introduces full text search notions and describes the installation and use of the RCL application. It is updated for RCL RCLVERSION.

RCL was for a long time dedicated to Unix-like systems. It was only lately (2015) ported to MS-Windows. Many references in this manual, especially file locations, are specific to Unix, and not valid on WIN, where some described features are also not available. The manual will be progressively updated. Until this happens, on WIN, most references to shared files can be translated by looking under the Recoll installation directory (esp. the Share subdirectory). The user configuration is stored by default under AppData/Local/Recoll inside the user directory, along with the index itself.

Giving it a try

If you do not like reading manuals (who does?) but wish to give RCL a try, just install the application and start the recoll graphical user interface (GUI), which will ask permission to index your home directory by default, allowing you to search immediately after indexing completes.

Do not do this if your home directory contains a huge number of documents and you do not want to wait or are very short on disk space. In this case, you may first want to customize the configuration to restrict the indexed area (for the very impatient with a completed package install, from the recoll GUI: Preferences > Indexing configuration, then adjust the Top directories section).

On Unix/Linux, you may need to install the appropriate supporting applications for document types that need them (for example antiword for Microsoft Word files).

The RCL for WIN package is self-contained and includes most useful auxiliary programs. You will just need to install Python 2.7.

Full text search

RCL is a full text search application, which means that it finds your data by content rather than by external attributes (like the file name). You specify words (terms) which should or should not appear in the text you are looking for, and receive in return a list of matching documents, ordered so that the most relevant documents will appear first.

You do not need to remember in what file or email message you stored a given piece of information. You just ask for related terms, and the tool will return a list of documents where these terms are prominent, in a similar way to Internet search engines.

Full text search applications try to determine which documents are most relevant to the search terms you provide. Computer algorithms for determining relevance can be very complex, and in general are inferior to the power of the human mind to rapidly determine relevance. The quality of relevance guessing is probably the most important aspect when evaluating a search application. RCL relies on the XAP probabilistic information retrieval library to determine relevance.

In many cases, you are looking for all the forms of a word, including plurals, different tenses for a verb, or terms derived from the same root or stem (example: floor, floors, floored, flooring...). Queries are usually automatically expanded to all such related terms (words that reduce to the same stem). This can be prevented for searching for a specific form.

Stemming, by itself, does not accommodate for misspellings or phonetic searches. A full text search application may also support this form of approximation. For example, a search for aliterattion returning no result might propose alliteration, alteration, alterations, or altercation as possible replacement terms. RCL bases its suggestions on the actual index contents, so that suggestions may be made for words which would not appear in a standard dictionary.

Recoll overview

RCL uses the XAP information retrieval library as its storage and retrieval engine. XAP is a very mature package using a sophisticated probabilistic ranking model.

The XAP library manages an index database which describes where terms appear in your document files. It efficiently processes the complex queries which are produced by the RCL query expansion mechanism, and is in charge of the all-important relevance computation task.

RCL provides the mechanisms and interface to get data into and out of the index. This includes translating the many possible document formats into pure text, handling term variations (using XAP stemmers), and spelling approximations (using the aspell speller), interpreting user queries and presenting results.

In a shorter way, RCL does the dirty footwork, XAP deals with the intelligent parts of the process.

The XAP index can be big (roughly the size of the original document set), but it is not a document archive. RCL can only display documents that still exist at the place from which they were indexed. (Actually, there is a way to reconstruct a document from the information in the index, but only the pure text is saved, possibly without punctuation and capitalization, depending on RCL version).

RCL stores all internal data in Unicode UTF-8 format, and it can index files of many types with different character sets, encodings, and languages into the same index. It can process documents embedded inside other documents (for example a pdf document stored inside a Zip archive sent as an email attachment...), down to an arbitrary depth.

Stemming is the process by which RCL reduces words to their radicals so that searching does not depend, for example, on a word being singular or plural (floor, floors), or on a verb tense (flooring, floored). Because the mechanisms used for stemming depend on the specific grammatical rules for each language, there is a separate XAP stemmer module for most common languages where stemming makes sense.

RCL stores the unstemmed versions of terms in the main index and uses auxiliary databases for term expansion (one for each stemming language), which means that you can switch stemming languages between searches, or add a language without needing a full reindex.

Storing documents written in different languages in the same index is possible, and commonly done. In this situation, you can specify several stemming languages for the index.

RCL currently makes no attempt at automatic language recognition, which means that the stemmer will sometimes be applied to terms from other languages with potentially strange results. In practise, even if this introduces possibilities of confusion, this approach has been proven quite useful, and it is much less cumbersome than separating your documents according to what language they are written in.

By default, RCL strips most accents and diacritics from terms, and converts them to lower case before either storing them in the index or searching for them. As a consequence, it is impossible to search for a particular capitalization of a term (US / us), or to discriminate two terms based on diacritics (sake / saké, mate / maté).

RCL can optionally store the raw terms, without accent stripping or case conversion. In this configuration, default searches will behave as before, but it is possible to perform searches sensitive to case and diacritics. This is described in more detail in the section about index case and diacritics sensitivity.

RCL has many parameters which define exactly what to index, and how to classify and decode the source documents. These are kept in configuration files. A default configuration is copied into a standard location (usually something like /usr/share/recoll/examples) during installation. The default values set by the configuration files in this directory may be overridden by values set inside your personal configuration, found by default in the .recoll sub-directory of your home directory. The default configuration will index your home directory with default parameters and should be sufficient for giving RCL a try, but you may want to adjust it later, which can be done either by editing the text files or by using configuration menus in the recoll GUI. Some other parameters affecting only the recoll GUI are stored in the standard location defined by Qt.

The indexing process is started automatically (after asking permission), the first time you execute the recoll GUI. Indexing can also be performed by executing the recollindex command. RCL indexing is multithreaded by default when appropriate hardware resources are available, and can perform in parallel multiple tasks for text extraction, segmentation and index updates.

Searches are usually performed inside the recoll GUI, which has many options to help you find what you are looking for. However, there are other ways to perform RCL searches:

Indexing

Introduction

Indexing is the process by which the set of documents is analyzed and the data entered into the database. RCL indexing is normally incremental: documents will only be processed if they have been modified since the last run. On the first execution, all documents will need processing. A full index build can be forced later by specifying an option to the indexing command (recollindex -z or -Z).

recollindex skips files which caused an error during a previous pass. This is a performance optimization, and a new behaviour in version 1.21 (failed files were always retried by previous versions). The command line option -k can be set to retry failed files, for example after updating an input handler.

The following sections give an overview of different aspects of the indexing processes and configuration, with links to detailed sections.

Depending on your data, temporary files may be needed during indexing, some of them possibly quite big. You can use the RECOLL_TMPDIR or TMPDIR environment variables to determine where they are created (the default is to use /tmp). Using TMPDIR has the nice property that it may also be taken into account by auxiliary commands executed by recollindex.

Indexing modes

RCL indexing can be performed along two main modes:

  • `Periodic (or batch) indexing: <#RCL.INDEXING.PERIODIC>`__.

    recollindex is executed at discrete times. The typical usage is to have a nightly run programmed into your cron file.

  • `Real time indexing: <#RCL.INDEXING.MONITOR>`__.

    recollindex runs permanently as a daemon and uses a file system alteration monitor (e.g. inotify) to detect file changes. New or updated files are indexed at once.

The choice between the two methods is mostly a matter of preference, and they can be combined by setting up multiple indexes (ie: use periodic indexing on a big documentation directory, and real time indexing on a small home directory). Monitoring a big file system tree can consume significant system resources.

With RCL 1.24 and newer, it is also possible to set up an index so that only a subset of the tree will be monitored and the rest will be covered by batch/incremental indexing. (See the details in the Real time indexing section.

The choice of method and the parameters used can be configured from the recoll GUI: Preferences > Indexing schedule

The GUI File menu also has entries to start or stop the current indexing operation. Stopping indexing is performed by killing the recollindex process, which will checkpoint its state and exit. A later restart of indexing will mostly resume from where things stopped (the file tree walk has to be restarted from the beginning).

When the real time indexer is running, two operations are available from the menu: ‘Stop’ and ‘Trigger incremental pass’. When no indexing is running, you have a choice of updating the index or rebuilding it (the first choice only processes changed files, the second one zeroes the index before starting so that all files are processed).

Configurations, multiple indexes

RCL supports defining multiple indexes, each defined by its own configuration directory, in which several configuration files describe what should be indexed and how.

A default personal configuration directory ($HOME/.recoll/) is created when a RCL program is first executed. This configuration is the one used for indexing and querying when no specific configuration is specified.

All configuration parameters have defaults, defined in system-wide files. Without further customisation, the default configuration will process your complete home directory, with a reasonable set of defaults. It can be changed to process a different area of the file system, select files in different ways, and many other things.

In some cases, it may be useful to create additional configuration directories, for example, to separate personal and shared indexes, or to take advantage of the organization of your data to improve search precision.

A plausible usage scenario for the multiple index feature would be for a system administrator to set up a central index for shared data, that you choose to search or not in addition to your personal data. Of course, there are other possibilities. for example, there are many cases where you know the subset of files that should be searched, and where narrowing the search can improve the results. You can achieve approximately the same effect with the directory filter in advanced search, but multiple indexes may have better performance and may be worth the trouble in some cases.

A more advanced use case would be to use multiple index to improve indexing performance, by updating several indexes in parallel (using multiple CPU cores and disks, or possibly several machines), and then merging them, or querying them in parallel.

A specific configuration can be selected by setting the RECOLL_CONFDIR environment variable, or giving the -c option to any of the RCL commands.

When creating or updating indexes, the different configurations are entirely independant (no parameters are ever shared between configurations when indexing). The recollindex program always works on a single index.

When querying, multiple indexes can be accessed concurrently, either from the GUI or the command line. When doing this, there is always one main configuration, from which both configuration and index data are used. Only the index data from the additional indexes is used (their configuration parameters are ignored).

The behaviour of index update and query regarding multiple configurations is important and sometimes confusing, so it will be rephrased here: for index generation, multiple configurations are totally independant from each other. When querying, configuration and data are used from the main index (the one designated by -c or RECOLL_CONFDIR), and only the data from the additional indexes is used. This implies that some parameters should be consistent among the configurations for indexes which are to be used together.

See the section about configuring multiple indexes for more detail

Document types

RCL knows about quite a few different document types. The parameters for document types recognition and processing are set in configuration files.

Most file types, like HTML or word processing files, only hold one document. Some file types, like email folders or zip archives, can hold many individually indexed documents, which may themselves be compound ones. Such hierarchies can go quite deep, and RCL can process, for example, a LibreOffice document stored as an attachment to an email message inside an email folder archived in a zip file...

recollindex processes plain text, HTML, OpenDocument (Open/LibreOffice), email formats, and a few others internally.

Other file types (ie: postscript, pdf, ms-word, rtf ...) need external applications for preprocessing. The list is in the installation section. After every indexing operation, RCL updates a list of commands that would be needed for indexing existing files types. This list can be displayed by selecting the menu option File > Show Missing Helpers in the recoll GUI. It is stored in the missing text file inside the configuration directory.

By default, RCL will try to index any file type that it has a way to read. This is sometimes not desirable, and there are ways to either exclude some types, or on the contrary define a positive list of types to be indexed. In the latter case, any type not in the list will be ignored.

Excluding files by name can be done by adding wildcard name patterns to the skippedNames list, which can be done from the GUI Index configuration menu. Excluding by type can be done by setting the excludedmimetypes list in the configuration file (1.20 and later). This can be redefined for subdirectories.

You can also define an exclusive list of MIME types to be indexed (no others will be indexed), by settting the indexedmimetypes configuration variable. Example:

indexedmimetypes = text/html application/pdf

It is possible to redefine this parameter for subdirectories. Example:

[/path/to/my/dir]
indexedmimetypes = application/pdf

(When using sections like this, don’t forget that they remain in effect until the end of the file or another section indicator).

excludedmimetypes or indexedmimetypes, can be set either by editing the configuration file (``recoll.conf`) <#RCL.INSTALL.CONFIG.RECOLLCONF>`__ for the index, or by using the GUI index configuration tool.

Note

When editing the indexedmimetypes or excludedmimetypes lists, you should use the MIME values listed in the mimemap file or in Recoll result lists in preference to file -i output: there are a number of differences. The file -i output should only be used for files without extensions, or for which the extension is not listed in mimemap

Indexing failures

Indexing may fail for some documents, for a number of reasons: a helper program may be missing, the document may be corrupt, we may fail to uncompress a file because no file system space is available, etc.

RCL versions prior to 1.21 always retried to index files which had previously caused an error. This guaranteed that anything that may have become indexable (for example because a helper had been installed) would be indexed. However this was bad for performance because some indexing failures may be quite costly (for example failing to uncompress a big file because of insufficient disk space).

The indexer in RCL versions 1.21 and later does not retry failed files by default. Retrying will only occur if an explicit option (-k) is set on the recollindex command line, or if a script executed when recollindex starts up says so. The script is defined by a configuration variable (checkneedretryindexscript), and makes a rather lame attempt at deciding if a helper command may have been installed, by checking if any of the common bin directories have changed.

Recovery

In the rare case where the index becomes corrupted (which can signal itself by weird search results or crashes), the index files need to be erased before restarting a clean indexing pass. Just delete the xapiandb directory (see next section), or, alternatively, start the next recollindex with the -z option, which will reset the database before indexing. The difference between the two methods is that the second will not change the current index format, which may be undesirable if a newer format is supported by the XAP version.

Index storage

The default location for the index data is the xapiandb subdirectory of the RCL configuration directory, typically $HOME/.recoll/xapiandb/. This can be changed via two different methods (with different purposes):

  1. For a given configuration directory, you can specify a non-default storage location for the index by setting the dbdir parameter in the configuration file (see the configuration section). This method would mainly be of use if you wanted to keep the configuration directory in its default location, but desired another location for the index, typically out of disk occupation or performance concerns.

  2. You can specify a different configuration directory by setting the RECOLL_CONFDIR environment variable, or using the -c option to the RCL commands. This method would typically be used to index different areas of the file system to different indexes. For example, if you were to issue the following command:

    recoll -c ~/.indexes-email

    Then RCL would use configuration files stored in ~/.indexes-email/ and, (unless specified otherwise in recoll.conf) would look for the index in ~/.indexes-email/xapiandb/.

    Using multiple configuration directories and configuration options allows you to tailor multiple configurations and indexes to handle whatever subset of the available data you wish to make searchable.

The size of the index is determined by the size of the set of documents, but the ratio can vary a lot. For a typical mixed set of documents, the index size will often be close to the data set size. In specific cases (a set of compressed mbox files for example), the index can become much bigger than the documents. It may also be much smaller if the documents contain a lot of images or other non-indexed data (an extreme example being a set of mp3 files where only the tags would be indexed).

Of course, images, sound and video do not increase the index size, which means that in most cases, the space used by the index will be negligible against the total amount of data on the computer.

The index data directory (xapiandb) only contains data that can be completely rebuilt by an index run (as long as the original documents exist), and it can always be destroyed safely.

XAP index formats

XAP versions usually support several formats for index storage. A given major XAP version will have a current format, used to create new indexes, and will also support the format from the previous major version.

XAP will not convert automatically an existing index from the older format to the newer one. If you want to upgrade to the new format, or if a very old index needs to be converted because its format is not supported any more, you will have to explicitly delete the old index (typically ~/.recoll/xapiandb), then run a normal indexing command. Using recollindex option -z would not work in this situation.

Security aspects

The RCL index does not hold complete copies of the indexed documents (it almost does after version 1.24). But it does hold enough data to allow for an almost complete reconstruction. If confidential data is indexed, access to the database directory should be restricted.

RCL will create the configuration directory with a mode of 0700 (access by owner only). As the index data directory is by default a sub-directory of the configuration directory, this should result in appropriate protection.

If you use another setup, you should think of the kind of protection you need for your index, set the directory and files access modes appropriately, and also maybe adjust the umask used during index updates.

Special considerations for big indexes

This only needs concern you if your index is going to be bigger than around 5 GBytes. Beyond 10 GBytes, it becomes a serious issue. Most people have much smaller indexes. For reference, 5 GBytes would be around 2000 bibles, a lot of text. If you have a huge text dataset (remember: images don’t count, the text content of PDFs is typically less than 5% of the file size), read on.

The amount of writing performed by Xapian during index creation is not linear with the index size (it is somewhere between linear and quadratic). For big indexes this becomes a performance issue, and may even be an SSD disk wear issue.

The problem can be mitigated by observing the following rules:

  • Partition the data set and create several indexes of reasonable size rather than a huge one. These indexes can then be queried in parallel (using the RCL external indexes facility), or merged using xapian-compact.
  • Have a lot of RAM available and set the idxflushmb RCL configuration parameter as high as you can without swapping (experimentation will be needed). 200 would be a minimum in this context.
  • Use Xapian 1.4.10 or newer, as this version brought a significant improvement in the amount of writes.

Index configuration

Variables set inside the RCL configuration files control which areas of the file system are indexed, and how files are processed. These variables can be set either by editing the text files or by using the dialogs in the ``recoll` GUI <#RCL.INDEXING.CONFIG.GUI>`__.

The first time you start recoll, you will be asked whether or not you would like it to build the index. If you want to adjust the configuration before indexing, just click Cancel at this point, which will get you into the configuration interface. If you exit at this point, recoll will have created a ~/.recoll directory containing empty configuration files, which you can edit by hand.

The configuration is documented inside the installation chapter of this document, or in the recoll.conf 5 man page, but the most current information will most likely be the comments inside the sample file. The most immediately useful variable is probably `topdirs <#RCL.INSTALL.CONFIG.RECOLLCONF.TOPDIRS>`__, which determines what subtrees and files get indexed.

The applications needed to index file types other than text, HTML or email (ie: pdf, postscript, ms-word...) are described in the external packages section.

As of Recoll 1.18 there are two incompatible types of Recoll indexes, depending on the treatment of character case and diacritics. A further section describes the two types in more detail.

Multiple indexes

Multiple RCL indexes can be created by using several configuration directories which are typically set to index different areas of the file system. A specific index can be selected for updating or searching, using the RECOLL_CONFDIR environment variable or the -c option to recoll and recollindex.

Index configuration parameters can be set either by using a text editor on the files, or, for most parameters, by using the recoll index configuration GUI. In the latter case, the configuration directory for which parameters are modified is the one which was selected by RECOLL_CONFDIR or the -c parameter, and there is no way to switch configurations within the GUI.

As a remainder from a previous section, a recollindex program instance can only update one specific index, and it will only use parameters from a single configuration (no parameters are ever shared between configurations when indexing). All the query methods (recoll, recollq, the Python API, etc.) operate with a main configuration, from which both configuration and index data are used, but can also query data from multiple additional indexes. Only the index data from the latter is used, their configuration parameters are ignored.

When searching, the current main index (defined by RECOLL_CONFDIR or -c) is always active. If this is undesirable, you can set up your base configuration to index an empty directory.

If a set of multiple indexes are to be used together for searches, some configuration parameters must be consistent among the set. These are parameters which need to be the same when indexing and searching. As the parameters come from the main configuration when searching, they need to be compatible with what was set when creating the other indexes (which came from their respective configuration directories).

Most importantly, all indexes to be queried concurrently must have the same option concerning character case and diacritics stripping, but there are other constraints. Most of the relevant parameters are described in the linked section.

The different search interfaces (GUI, command line, ...) have different methods to define the set of indexes to be used, see the appropriate section.

At the moment, using multiple configurations implies a small level of command line usage. Additional configuration directories (beyond ~/.recoll) must be created by hand (mkdir or such), the GUI will not do it. This is to avoid mistakenly creating additional directories when an argument is mistyped. Also, the GUI or the indexer must be launched with a specific option or environment to work on the right configuration.

To be more practical, here follows a few examples of the commands need to create, configure, update, and query an additional index.

Initially creating the configuration and index:

mkdir /path/to/my/new/config

Configuring the new index can be done from the recoll GUI, launched from the command line to pass the -c option (you could create a desktop file to do it for you), and then using the GUI index configuration tool to set up the index.

recoll -c /path/to/my/new/config

Alternatively, you can just start a text editor on the main configuration file ```recoll.conf

`` <#RCL.INSTALL.CONFIG.RECOLLCONF>`__.

Creating and updating the index can be done from the command line:

recollindex -c /path/to/my/new/config

or from the File menu of a GUI launched with the same option (recoll, see above).

The same GUI would also let you set up batch indexing for the new index. Real time indexing can only be set up from the GUI for the default index (the menu entry will be inactive if the GUI was started with a non-default -c option).

The new index can be queried alone with

recoll -c /path/to/my/new/config

Or, in parallel with the default index, by starting recoll without a -c option, and using the Preferences > External Index Dialog menu.

Index case and diacritics sensitivity

As of RCL version 1.18 you have a choice of building an index with terms stripped of character case and diacritics, or one with raw terms. For a source term of Résumé, the former will store resume, the latter Résumé.

Each type of index allows performing searches insensitive to case and diacritics: with a raw index, the user entry will be expanded to match all case and diacritics variations present in the index. With a stripped index, the search term will be stripped before searching.

A raw index allows for another possibility which a stripped index cannot offer: using case and diacritics to discriminate between terms, returning different results when searching for US and us or resume and résumé. Read the section about search case and diacritics sensitivity for more details.

The type of index to be created is controlled by the indexStripChars configuration variable which can only be changed by editing the configuration file. Any change implies an index reset (not automated by RCL), and all indexes in a search must be set in the same way (again, not checked by RCL).

If the indexStripChars is not set, RCL 1.18 creates a stripped index by default, for compatibility with previous versions.

As a cost for added capability, a raw index will be slightly bigger than a stripped one (around 10%). Also, searches will be more complex, so probably slightly slower, and the feature is still young, so that a certain amount of weirdness cannot be excluded.

One of the most adverse consequence of using a raw index is that some phrase and proximity searches may become impossible: because each term needs to be expanded, and all combinations searched for, the multiplicative expansion may become unmanageable.

Indexing threads configuration

The RCL indexing process recollindex can use multiple threads to speed up indexing on multiprocessor systems. The work done to index files is divided in several stages and some of the stages can be executed by multiple threads. The stages are:

  1. File system walking: this is always performed by the main thread.
  2. File conversion and data extraction.
  3. Text processing (splitting, stemming, etc.).
  4. XAP index update.

You can also read a longer document about the transformation of RCL indexing to multithreading.

The threads configuration is controlled by two configuration file parameters.

thrQSizes
This variable defines the job input queues configuration. There are three possible queues for stages 2, 3 and 4, and this parameter should give the queue depth for each stage (three integer values). If a value of -1 is used for a given stage, no queue is used, and the thread will go on performing the next stage. In practise, deep queues have not been shown to increase performance. A value of 0 for the first queue tells RCL to perform autoconfiguration (no need for anything else in this case, thrTCounts is not used) - this is the default configuration.
thrTCounts

This defines the number of threads used for each stage. If a value of -1 is used for one of the queue depths, the corresponding thread count is ignored. It makes no sense to use a value other than 1 for the last stage because updating the XAP index is necessarily single-threaded (and protected by a mutex).

Note

If the first value in thrQSizes is 0, thrTCounts is ignored.

The following example would use three queues (of depth 2), and 4 threads for converting source documents, 2 for processing their text, and one to update the index. This was tested to be the best configuration on the test system (quadri-processor with multiple disks).

thrQSizes = 2 2 2
thrTCounts =  4 2 1

The following example would use a single queue, and the complete processing for each document would be performed by a single thread (several documents will still be processed in parallel in most cases). The threads will use mutual exclusion when entering the index update stage. In practise the performance would be close to the precedent case in general, but worse in certain cases (e.g. a Zip archive would be performed purely sequentially), so the previous approach is preferred. YMMV... The 2 last values for thrTCounts are ignored.

thrQSizes = 2 -1 -1
thrTCounts =  6 1 1

The following example would disable multithreading. Indexing will be performed by a single thread.

thrQSizes = -1 -1 -1

The index configuration GUI

Most parameters for a given index configuration can be set from a recoll GUI running on this configuration (either as default, or by setting RECOLL_CONFDIR or the -c option.)

The interface is started from the Preferences > Index Configuration menu entry. It is divided in four tabs, Global parameters, Local parameters, Web history (which is explained in the next section) and Search parameters.

The Global parameters tab allows setting global variables, like the lists of top directories, skipped paths, or stemming languages.

The Local parameters tab allows setting variables that can be redefined for subdirectories. This second tab has an initially empty list of customisation directories, to which you can add. The variables are then set for the currently selected directory (or at the top level if the empty line is selected).

The Search parameters section defines parameters which are used at query time, but are global to an index and affect all search tools, not only the GUI.

The meaning for most entries in the interface is self-evident and documented by a ToolTip popup on the text label. For more detail, you will need to refer to the configuration section of this guide.

The configuration tool normally respects the comments and most of the formatting inside the configuration file, so that it is quite possible to use it on hand-edited files, which you might nevertheless want to backup first...

Indexing the WEB pages which you wisit.

With the help of a Firefox extension, RCL can index the Internet pages that you visit. The extension has a long history: it was initially designed for the Beagle indexer, then adapted to RCL and the Firefox XUL API. A new version of the addon has been written to work with the WebExtensions API, which is the only one supported after Firefox version 57.

The extension works by copying visited WEB pages to an indexing queue directory, which RCL then processes, indexing the data, storing it into a local cache, then removing the file from the queue.

Because the WebExtensions API introduces more constraints to what extensions can do, the new version works with one more step: the files are first created in the browser default downloads location (typically $HOME/Downloads ), then moved by a script in the old queue location. The script is automatically executed by the RCL indexer versions 1.23.5 and newer. It could conceivably be executed independantly to make the new browser extension compatible with an older RCL version (the script is named recoll-we-move-files.py).

Note

For the WebExtensions-based version to work, it is necessary to set the webdownloadsdir value in the configuration if it was changed from the default $HOME/Downloads in the browser preferences.

The visited WEB pages indexing feature can be enabled on the RCL side from the GUI Index configuration panel, or by editing the configuration file (set processwebqueue to 1).

A current pointer to the extension can be found, along with up-to-date instructions, on the Recoll wiki.

A copy of the indexed WEB pages is retained by Recoll in a local cache (from which previews can be fetched). The cache size can be adjusted from the Index configuration / Web history panel. Once the maximum size is reached, old pages are purged - both from the cache and the index - to make room for new ones, so you need to explicitly archive in some other place the pages that you want to keep indefinitely.

Extended attributes data

User extended attributes are named pieces of information that most modern file systems can attach to any file.

RCL versions 1.19 and later process extended attributes as document fields by default. For older versions, this has to be activated at build time.

A freedesktop standard defines a few special attributes, which are handled as such by RCL:

mime_type
If set, this overrides any other determination of the file MIME type.
charset
If set, this defines the file character set (mostly useful for plain text files).

By default, other attributes are handled as RCL fields. On Linux, the user prefix is removed from the name. This can be configured more precisely inside the `fields configuration file <#RCL.INSTALL.CONFIG.FIELDS>`__.

Importing external tags

During indexing, it is possible to import metadata for each file by executing commands. For example, this could extract user tag data for the file and store it in a field for indexing.

See the section about the ``metadatacmds` field <#RCL.INSTALL.CONFIG.RECOLLCONF.METADATACMDS>`__ in the main configuration chapter for a description of the configuration syntax.

As an example, if you would want RCL to use tags managed by tmsu, you would add the following to the configuration file:

[/some/area/of/the/fs]
      metadatacmds = ; tags = tmsu tags %f


**Note**

Depending on the tmsu version, you may need/want to add options like
``--database=/some/db``.

You may want to restrict this processing to a subset of the directory tree, because it may slow down indexing a bit ([some/area/of/the/fs]).

Note the initial semi-colon after the equal sign.

In the example above, the output of tmsu is used to set a field named tags. The field name is arbitrary and could be tmsu or myfield just the same, but tags is an alias for the standard RCL keywords field, and the tmsu output will just augment its contents. This will avoid the need to extend the field configuration.

Once re-indexing is performed (you’ll need to force the file reindexing, RCL will not detect the need by itself), you will be able to search from the query language, through any of its aliases: tags:some/alternate/values or tags:all,these,values (the compact field search syntax is supported for recoll 1.20 and later. For older versions, you would need to repeat the tags: specifier for each term, e.g. ``tags:some OR

tags:alternate``).

You should be aware that tags changes will not be detected by the indexer if the file itself did not change. One possible workaround would be to update the file ctime when you modify the tags, which would be consistent with how extended attributes function. A pair of chmod commands could accomplish this, or a touch -a . Alternatively, just couple the tag update with a ``recollindex -e -i

filename.``

The PDF input handler

The PDF format is very important for scientific and technical documentation, and document archival. It has extensive facilities for storing metadata along with the document, and these facilities are actually used in the real world.

In consequence, the rclpdf.py PDF input handler has more complex capabilities than most others, and it is also more configurable. Specifically, rclpdf.py can automatically use tesseract to perform OCR if the document text is empty, it can be configured to extract specific metadata tags from an XMP packet, and to extract PDF attachments.

OCR with Tesseract

If both tesseract and pdftoppm (generally from the poppler-utils package) are installed, the PDF handler may attempt OCR on PDF files with no text content. This is controlled by the pdfocr configuration variable, which is false by default because OCR is very slow.

The choice of language is very important for successfull OCR. Recoll has currently no way to determine this from the document itself. You can set the language to use through the contents of a .ocrpdflang text file in the same directory as the PDF document, or through the RECOLL_TESSERACT_LANG environment variable, or through the contents of an ocrpdf text file inside the configuration directory. If none of the above are used, RCL will try to guess the language from the NLS environment.

XMP fields extraction

The rclpdf.py script in RCL version 1.23.2 and later can extract XMP metadata fields by executing the pdfinfo command (usually found with poppler-utils). This is controlled by the pdfextrameta configuration variable, which specifies which tags to extract and, possibly, how to rename them.

The pdfextrametafix variable can be used to designate a file with Python code to edit the metadata fields (available for RCL 1.23.3 and later. 1.23.2 has equivalent code inside the handler script). Example:

import sys
        import re

        class MetaFixer(object):
        def __init__(self):
        pass

        def metafix(self, nm, txt):
        if nm == 'bibtex:pages':
        txt = re.sub(r'--', '-', txt)
        elif nm == 'someothername':
        # do something else
        pass
        elif nm == 'stillanother':
        # etc.
        pass

        return txt
        def wrapup(self, metaheaders):
        pass

If the ‘metafix()’ method is defined, it is called for each metadata field. A new MetaFixer object is created for each PDF document (so the object can keep state for, for example, eliminating duplicate values). If the ‘wrapup()’ method is defined, it is called at the end of XMP fields processing with the whole metadata as parameter, as an array of ‘(nm, val)’ pairs, allowing an alternate approach for editing or adding/deleting fields.

PDF attachment indexing

If pdftk is installed, and if the the pdfattach configuration variable is set, the PDF input handler will try to extract PDF attachements for indexing as sub-documents of the PDF file. This is disabled by default, because it slows down PDF indexing a bit even if not one attachment is ever found (PDF attachments are uncommon in my experience).

Periodic indexing

Running indexing

Indexing is always performed by the recollindex program, which can be started either from the command line or from the File menu in the recoll GUI program. When started from the GUI, the indexing will run on the same configuration recoll was started on. When started from the command line, recollindex will use the RECOLL_CONFDIR variable or accept a -c confdir option to specify a non-default configuration directory.

If the recoll program finds no index when it starts, it will automatically start indexing (except if canceled).

The recollindex indexing process can be interrupted by sending an interrupt (Ctrl-C, SIGINT) or terminate (SIGTERM) signal. Some time may elapse before the process exits, because it needs to properly flush and close the index. This can also be done from the recoll GUI File > Stop Indexing menu entry.

After such an interruption, the index will be somewhat inconsistent because some operations which are normally performed at the end of the indexing pass will have been skipped (for example, the stemming and spelling databases will be inexistant or out of date). You just need to restart indexing at a later time to restore consistency. The indexing will restart at the interruption point (the full file tree will be traversed, but files that were indexed up to the interruption and for which the index is still up to date will not need to be reindexed).

recollindex has a number of other options which are described in its man page. Only a few will be described here.

Option -z will reset the index when starting. This is almost the same as destroying the index files (the nuance is that the XAP format version will not be changed).

Option -Z will force the update of all documents without resetting the index first. This will not have the “clean start” aspect of -z, but the advantage is that the index will remain available for querying while it is rebuilt, which can be a significant advantage if it is very big (some installations need days for a full index rebuild).

Option -k will force retrying files which previously failed to be indexed, for example because of a missing helper program.

Of special interest also, maybe, are the -i and -f options. -i allows indexing an explicit list of files (given as command line parameters or read on stdin). -f tells recollindex to ignore file selection parameters from the configuration. Together, these options allow building a custom file selection process for some area of the file system, by adding the top directory to the skippedPaths list and using an appropriate file selection method to build the file list to be fed to recollindex -if. Trivial example:

find . -name indexable.txt -print | recollindex -if

recollindex -i will not descend into subdirectories specified as parameters, but just add them as index entries. It is up to the external file selection method to build the complete file list.

Using cron to automate indexing

The most common way to set up indexing is to have a cron task execute it every night. For example the following crontab entry would do it every day at 3:30AM (supposing recollindex is in your PATH):

30 3 * * * recollindex > /some/tmp/dir/recolltrace 2>&1

Or, using anacron:

1  15  su mylogin -c "recollindex recollindex > /tmp/rcltraceme 2>&1"

As of version 1.17 the RCL GUI has dialogs to manage crontab entries for recollindex. You can reach them from the Preferences > Indexing Schedule menu. They only work with the good old cron, and do not give access to all features of cron scheduling.

The usual command to edit your crontab is crontab -e (which will usually start the vi editor to edit the file). You may have more sophisticated tools available on your system.

Please be aware that there may be differences between your usual interactive command line environment and the one seen by crontab commands. Especially the PATH variable may be of concern. Please check the crontab manual pages about possible issues.

Real time indexing

Real time monitoring/indexing is performed by starting the recollindex -m command. With this option, recollindex will detach from the terminal and become a daemon, permanently monitoring file changes and updating the index.

While it is convenient that data is indexed in real time, repeated indexing can generate a significant load on the system when files such as email folders change. Also, monitoring large file trees by itself significantly taxes system resources. You probably do not want to enable it if your system is short on resources. Periodic indexing is adequate in most cases.

As of RCL 1.24, you can set the monitordirs configuration variable to specify that only a subset of your indexed files will be monitored for instant indexing. In this situation, an incremental pass on the full tree can be triggered by either restarting the indexer, or just running recollindex, which will notify the running process. The recoll GUI also has a menu entry for this.

Real time indexing: automatic daemon start

Under KDE, Gnome and some other desktop environments, the daemon can automatically started when you log in, by creating a desktop file inside the ~/.config/autostart directory. This can be done for you by the RCL GUI. Use the Preferences->Indexing Schedule menu.

With older X11 setups, starting the daemon is normally performed as part of the user session script.

The rclmon.sh script can be used to easily start and stop the daemon. It can be found in the examples directory (typically /usr/local/[share/]recoll/examples).

For example, my out of fashion xdm-based session has a .xsession script with the following lines at the end:

recollconf=$HOME/.recoll-home
        recolldata=/usr/local/share/recoll
        RECOLL_CONFDIR=$recollconf $recolldata/examples/rclmon.sh start

        fvwm

The indexing daemon gets started, then the window manager, for which the session waits.

By default the indexing daemon will monitor the state of the X11 session, and exit when it finishes, it is not necessary to kill it explicitly. (The X11 server monitoring can be disabled with option -x to recollindex).

If you use the daemon completely out of an X11 session, you need to add option -x to disable X11 session monitoring (else the daemon will not start).

Real time indexing: miscellaneous details

By default, the messages from the indexing daemon will be sent to the same file as those from the interactive commands (logfilename). You may want to change this by setting the daemlogfilename and daemloglevel configuration parameters. Also the log file will only be truncated when the daemon starts. If the daemon runs permanently, the log file may grow quite big, depending on the log level.

When building RCL, the real time indexing support can be customised during package configuration with the --with[out]-fam or --with[out]-inotify options. The default is currently to include inotify monitoring on systems that support it, and, as of RCL 1.17, gamin support on FreeBSD.

Note

On Linux systems, monitoring a big tree may need increasing the resources available to inotify, which are normally defined in /etc/sysctl.conf.

### inotify
#
# cat  /proc/sys/fs/inotify/max_queued_events   - 16384
# cat  /proc/sys/fs/inotify/max_user_instances  - 128
# cat  /proc/sys/fs/inotify/max_user_watches    - 16384
#
# -- Change to:
#
fs.inotify.max_queued_events=32768
fs.inotify.max_user_instances=256
fs.inotify.max_user_watches=32768

Especially, you will need to trim your tree or adjust the max_user_watches value if indexing exits with a message about errno ENOSPC (28) from inotify_add_watch.

Note

When using the real time monitor, it may happen that some files need to be indexed, but change so often that they impose an excessive load for the system.

RCL provides a configuration option to specify the minimum time before which a file, specified by a wildcard pattern, cannot be reindexed. See the mondelaypatterns parameter in the configuration section.

Searching

Searching with the Qt graphical user interface

The recoll program provides the main user interface for searching. It is based on the Qt library.

recoll has two search modes:

  • Simple search (the default, on the main screen) has a single entry field where you can enter multiple words.
  • Advanced search (a panel accessed through the Tools menu or the toolbox bar icon) has multiple entry fields, which you may use to build a logical condition, with additional filtering on file type, location in the file system, modification date, and size.

In most cases, you can enter the terms as you think them, even if they contain embedded punctuation or other non-textual characters. For example, RCL can handle things like email addresses, or arbitrary cut and paste from another text window, punctation and all.

The main case where you should enter text differently from how it is printed is for east-asian languages (Chinese, Japanese, Korean). Words composed of single or multiple characters should be entered separated by white space in this case (they would typically be printed without white space).

Some searches can be quite complex, and you may want to re-use them later, perhaps with some tweaking. RCL versions 1.21 and later can save and restore searches, using XML files. See Saving and restoring queries.

The default result list

After starting a search, a list of results will instantly be displayed in the main list window.

By default, the document list is presented in order of relevance (how well the system estimates that the document matches the query). You can sort the result by ascending or descending date by using the vertical arrows in the toolbar.

Clicking on the Preview link for an entry will open an internal preview window for the document. Further Preview clicks for the same search will open tabs in the existing preview window. You can use Shift+Click to force the creation of another preview window, which may be useful to view the documents side by side. (You can also browse successive results in a single preview window by typing Shift+ArrowUp/Down in the window).

Clicking the Open link will start an external viewer for the document. By default, RCL lets the desktop choose the appropriate application for most document types (there is a short list of exceptions, see further). If you prefer to completely customize the choice of applications, you can uncheck the Use desktop preferences option in the GUI preferences dialog, and click the Choose editor applications button to adjust the predefined RCL choices. The tool accepts multiple selections of MIME types (e.g. to set up the editor for the dozens of office file types).

Even when Use desktop preferences is checked, there is a small list of exceptions, for MIME types where the RCL choice should override the desktop one. These are applications which are well integrated with RCL, especially evince for viewing PDF and Postscript files because of its support for opening the document at a specific page and passing a search string as an argument. Of course, you can edit the list (in the GUI preferences) if you would prefer to lose the functionality and use the standard desktop tool.

You may also change the choice of applications by editing the `mimeview <#RCL.INSTALL.CONFIG.MIMEVIEW>`__ configuration file if you find this more convenient.

Each result entry also has a right-click menu with an Open With entry. This lets you choose an application from the list of those which registered with the desktop for the document MIME type.

The Preview and Open edit links may not be present for all entries, meaning that RCL has no configured way to preview a given file type (which was indexed by name only), or no configured external editor for the file type. This can sometimes be adjusted simply by tweaking the `mimemap <#RCL.INSTALL.CONFIG.MIMEMAP>`__ and `mimeview <#RCL.INSTALL.CONFIG.MIMEVIEW>`__ configuration files (the latter can be modified with the user preferences dialog).

The format of the result list entries is entirely configurable by using the preference dialog to edit an HTML fragment.

You can click on the Query details link at the top of the results page to see the query actually performed, after stem expansion and other processing.

Double-clicking on any word inside the result list or a preview window will insert it into the simple search text.

The result list is divided into pages (the size of which you can change in the preferences). Use the arrow buttons in the toolbar or the links at the bottom of the page to browse the results.

No results: the spelling suggestions

When a search yields no result, and if the aspell dictionary is configured, RCL will try to check for misspellings among the query terms, and will propose lists of replacements. Clicking on one of the suggestions will replace the word and restart the search. You can hold any of the modifier keys (Ctrl, Shift, etc.) while clicking if you would rather stay on the suggestion screen because several terms need replacement.

The result list right-click menu

Apart from the preview and edit links, you can display a pop-up menu by right-clicking over a paragraph in the result list. This menu has the following entries:

  • Preview
  • Open
  • Open With
  • Run Script
  • Copy File Name
  • Copy Url
  • Save to File
  • Find similar
  • Preview Parent document
  • Open Parent document
  • Open Snippets Window

The Preview and Open entries do the same thing as the corresponding links.

Open With lets you open the document with one of the applications claiming to be able to handle its MIME type (the information comes from the .desktop files in /usr/share/applications).

Run Script allows starting an arbitrary command on the result file. It will only appear for results which are top-level files. See further for a more detailed description.

The Copy File Name and Copy Url copy the relevant data to the clipboard, for later pasting.

Save to File allows saving the contents of a result document to a chosen file. This entry will only appear if the document does not correspond to an existing file, but is a subdocument inside such a file (ie: an email attachment). It is especially useful to extract attachments with no associated editor.

The Open/Preview Parent document entries allow working with the higher level document (e.g. the email message an attachment comes from). RCL is sometimes not totally accurate as to what it can or can’t do in this area. For example the Parent entry will also appear for an email which is part of an mbox folder file, but you can’t actually visualize the mbox (there will be an error dialog if you try).

If the document is a top-level file, Open Parent will start the default file manager on the enclosing filesystem directory.

The Find similar entry will select a number of relevant term from the current document and enter them into the simple search field. You can then start a simple search, with a good chance of finding documents related to the current result. I can’t remember a single instance where this function was actually useful to me...

The Open Snippets Window entry will only appear for documents which support page breaks (typically PDF, Postscript, DVI). The snippets window lists extracts from the document, taken around search terms occurrences, along with the corresponding page number, as links which can be used to start the native viewer on the appropriate page. If the viewer supports it, its search function will also be primed with one of the search terms.

The result table

In RCL 1.15 and newer, the results can be displayed in spreadsheet-like fashion. You can switch to this presentation by clicking the table-like icon in the toolbar (this is a toggle, click again to restore the list).

Clicking on the column headers will allow sorting by the values in the column. You can click again to invert the order, and use the header right-click menu to reset sorting to the default relevance order (you can also use the sort-by-date arrows to do this).

Both the list and the table display the same underlying results. The sort order set from the table is still active if you switch back to the list mode. You can click twice on a date sort arrow to reset it from there.

The header right-click menu allows adding or deleting columns. The columns can be resized, and their order can be changed (by dragging). All the changes are recorded when you quit recoll

Hovering over a table row will update the detail area at the bottom of the window with the corresponding values. You can click the row to freeze the display. The bottom area is equivalent to a result list paragraph, with links for starting a preview or a native application, and an equivalent right-click menu. Typing Esc (the Escape key) will unfreeze the display.

Running arbitrary commands on result files (1.20 and later)

Apart from the Open and Open With operations, which allow starting an application on a result document (or a temporary copy), based on its MIME type, it is also possible to run arbitrary commands on results which are top-level files, using the Run Script entry in the results pop-up menu.

The commands which will appear in the Run Script submenu must be defined by .desktop files inside the scripts subdirectory of the current configuration directory.

Here follows an example of a .desktop file, which could be named for example, ~/.recoll/scripts/myscript.desktop (the exact file name inside the directory is irrelevant):

[Desktop Entry]
Type=Application
Name=MyFirstScript
Exec=/home/me/bin/tryscript %F
MimeType=*/*

The Name attribute defines the label which will appear inside the Run Script menu. The Exec attribute defines the program to be run, which does not need to actually be a script, of course. The MimeType attribute is not used, but needs to exist.

The commands defined this way can also be used from links inside the result paragraph.

As an example, it might make sense to write a script which would move the document to the trash and purge it from the RCL index.

Displaying thumbnails

The default format for the result list entries and the detail area of the result table display an icon for each result document. The icon is either a generic one determined from the MIME type, or a thumbnail of the document appearance. Thumbnails are only displayed if found in the standard freedesktop location, where they would typically have been created by a file manager.

Recoll has no capability to create thumbnails. A relatively simple trick is to use the Open parent document/folder entry in the result list popup menu. This should open a file manager window on the containing directory, which should in turn create the thumbnails (depending on your settings). Restarting the search should then display the thumbnails.

There are also some pointers about thumbnail generation on the RCL wiki.

The preview window

The preview window opens when you first click a Preview link inside the result list.

Subsequent preview requests for a given search open new tabs in the existing window (except if you hold the Shift key while clicking which will open a new window for side by side viewing).

Starting another search and requesting a preview will create a new preview window. The old one stays open until you close it.

You can close a preview tab by typing Ctrl-W (Ctrl + W) in the window. Closing the last tab for a window will also close the window.

Of course you can also close a preview window by using the window manager button in the top of the frame.

You can display successive or previous documents from the result list inside a preview tab by typing Shift+Down or Shift+Up (Down and Up are the arrow keys).

A right-click menu in the text area allows switching between displaying the main text or the contents of fields associated to the document (ie: author, abtract, etc.). This is especially useful in cases where the term match did not occur in the main text but in one of the fields. In the case of images, you can switch between three displays: the image itself, the image metadata as extracted by exiftool and the fields, which is the metadata stored in the index.

You can print the current preview window contents by typing Ctrl-P (Ctrl + P) in the window text.

Searching inside the preview

The preview window has an internal search capability, mostly controlled by the panel at the bottom of the window, which works in two modes: as a classical editor incremental search, where we look for the text entered in the entry zone, or as a way to walk the matches between the document and the RCL query that found it.

Incremental text search

The preview tabs have an internal incremental search function. You initiate the search either by typing a / (slash) or CTL-F inside the text area or by clicking into the Search for: text field and entering the search string. You can then use the Next and Previous buttons to find the next/previous occurrence. You can also type F3 inside the text area to get to the next occurrence.

If you have a search string entered and you use Ctrl-Up/Ctrl-Down to browse the results, the search is initiated for each successive document. If the string is found, the cursor will be positioned at the first occurrence of the search string.

Walking the match lists
If the entry area is empty when you click the Next or Previous buttons, the editor will be scrolled to show the next match to any search term (the next highlighted zone). If you select a search group from the dropdown list and click Next or Previous, the match list for this group will be walked. This is not the same as a text search, because the occurences will include non-exact matches (as caused by stemming or wildcards). The search will revert to the text mode as soon as you edit the entry area.

The Query Fragments window

Selecting the Tools > Query Fragments menu entry will open a window with radio- and check-buttons which can be used to activate query language fragments for filtering the current query. This can be useful if you have frequent reusable selectors, for example, filtering on alternate directories, or searching just one category of files, not covered by the standard category selectors.

The contents of the window are entirely customizable, and defined by the contents of the fragbuts.xml file inside the configuration directory. The sample file distributed with RCL (which you should be able to find under /usr/share/recoll/examples/fragbuts.xml), contains an example which filters the results from the WEB history.

Here follows an example:

<?xml version="1.0" encoding="UTF-8"?>

<fragbuts version="1.0">

<radiobuttons>

<fragbut>
<label>Include Web Results</label>
<frag></frag>
</fragbut>

<fragbut>
<label>Exclude Web Results</label>
<frag>-rclbes:BGL</frag>
</fragbut>

<fragbut>
<label>Only Web Results</label>
<frag>rclbes:BGL</frag>
</fragbut>

</radiobuttons>

<buttons>

<fragbut>
<label>Year 2010</label>
<frag>date:2010-01-01/2010-12-31</frag>
</fragbut>

<fragbut>
<label>My Great Directory Only</label>
<frag>dir:/my/great/directory</frag>
</fragbut>

</buttons>
</fragbuts>

Each radiobuttons or buttons section defines a line of checkbuttons or radiobuttons inside the window. Any number of buttons can be selected, but the radiobuttons in a line are exclusive.

Each fragbut section defines the label for a button, and the Query Language fragment which will be added (as an AND filter) before performing the query if the button is active.

This feature is new in RCL 1.20, and will probably be refined depending on user feedback.

The term explorer tool

RCL automatically manages the expansion of search terms to their derivatives (ie: plural/singular, verb inflections). But there are other cases where the exact search term is not known. For example, you may not remember the exact spelling, or only know the beginning of the name.

The search will only propose replacement terms with spelling variations when no matching document were found. In some cases, both proper spellings and mispellings are present in the index, and it may be interesting to look for them explicitely.

The term explorer tool (started from the toolbar icon or from the Term explorer entry of the Tools menu) can be used to search the full index terms list. It has three modes of operations:

Wildcard
In this mode of operation, you can enter a search string with shell-like wildcards (*, ?, []). ie: xapi* would display all index terms beginning with xapi. (More about wildcards here).
Regular expression
This mode will accept a regular expression as input. Example: word[0-9]+. The expression is implicitely anchored at the beginning. Ie: press will match pression but not expression. You can use .*press to match the latter, but be aware that this will cause a full index term list scan, which can be quite long.
Stem expansion
This mode will perform the usual stem expansion normally done as part user input processing. As such it is probably mostly useful to demonstrate the process.
Spelling/Phonetic
In this mode, you enter the term as you think it is spelled, and RCL will do its best to find index terms that sound like your entry. This mode uses the Aspell spelling application, which must be installed on your system for things to work (if your documents contain non-ascii characters, RCL needs an aspell version newer than 0.60 for UTF-8 support). The language which is used to build the dictionary out of the index terms (which is done at the end of an indexing pass) is the one defined by your NLS environment. Weird things will probably happen if languages are mixed up.

Note that in cases where RCL does not know the beginning of the string to search for (ie a wildcard expression like *coll), the expansion can take quite a long time because the full index term list will have to be processed. The expansion is currently limited at 10000 results for wildcards and regular expressions. It is possible to change the limit in the configuration file.

Double-clicking on a term in the result list will insert it into the simple search entry field. You can also cut/paste between the result list and any entry field (the end of lines will be taken care of).

Multiple indexes

See the section describing the use of multiple indexes for generalities. Only the aspects concerning the recoll GUI are described here.

A recoll program instance is always associated with a specific index, which is the one to be updated when requested from the File menu, but it can use any number of RCL indexes for searching. The external indexes can be selected through the external indexes tab in the preferences dialog.

Index selection is performed in two phases. A set of all usable indexes must first be defined, and then the subset of indexes to be used for searching. These parameters are retained across program executions (there are kept separately for each RCL configuration). The set of all indexes is usually quite stable, while the active ones might typically be adjusted quite frequently.

The main index (defined by RECOLL_CONFDIR) is always active. If this is undesirable, you can set up your base configuration to index an empty directory.

When adding a new index to the set, you can select either a RCL configuration directory, or directly a XAP index directory. In the first case, the XAP index directory will be obtained from the selected configuration.

As building the set of all indexes can be a little tedious when done through the user interface, you can use the RECOLL_EXTRA_DBS environment variable to provide an initial set. This might typically be set up by a system administrator so that every user does not have to do it. The variable should define a colon-separated list of index directories, ie:

export RECOLL_EXTRA_DBS=/some/place/xapiandb:/some/other/db

Another environment variable, RECOLL_ACTIVE_EXTRA_DBS allows adding to the active list of indexes. This variable was suggested and implemented by a RCL user. It is mostly useful if you use scripts to mount external volumes with RCL indexes. By using RECOLL_EXTRA_DBS and RECOLL_ACTIVE_EXTRA_DBS, you can add and activate the index for the mounted volume when starting recoll.

RECOLL_ACTIVE_EXTRA_DBS is available for RCL versions 1.17.2 and later. A change was made in the same update so that recoll will automatically deactivate unreachable indexes when starting up.

Document history

Documents that you actually view (with the internal preview or an external tool) are entered into the document history, which is remembered.

You can display the history list by using the Tools/Doc History menu entry.

You can erase the document history by using the Erase document history entry in the File menu.

Sorting search results and collapsing duplicates

The documents in a result list are normally sorted in order of relevance. It is possible to specify a different sort order, either by using the vertical arrows in the GUI toolbox to sort by date, or switching to the result table display and clicking on any header. The sort order chosen inside the result table remains active if you switch back to the result list, until you click one of the vertical arrows, until both are unchecked (you are back to sort by relevance).

Sort parameters are remembered between program invocations, but result sorting is normally always inactive when the program starts. It is possible to keep the sorting activation state between program invocations by checking the Remember sort activation state option in the preferences.

It is also possible to hide duplicate entries inside the result list (documents with the exact same contents as the displayed one). The test of identity is based on an MD5 hash of the document container, not only of the text contents (so that ie, a text document with an image added will not be a duplicate of the text only). Duplicates hiding is controlled by an entry in the GUI configuration dialog, and is off by default.

As of release 1.19, when a result document does have undisplayed duplicates, a Dups link will be shown with the result list entry. Clicking the link will display the paths (URLs + ipaths) for the duplicate entries.

Search tips, shortcuts

Terms and search expansion

Term completion.

Typing Esc Space in the simple search entry field while entering a word will either complete the current word if its beginning matches a unique term in the index, or open a window to propose a list of completions.

Picking up new terms from result or preview text.

Double-clicking on a word in the result list or in a preview window will copy it to the simple search entry field.

Wildcards.

Wildcards can be used inside search terms in all forms of searches. More about wildcards.

Automatic suffixes.

Words like odt or ods can be automatically turned into query language ext:xxx clauses. This can be enabled in the Search preferences panel in the GUI.

Disabling stem expansion.

Entering a capitalized word in any search field will prevent stem expansion (no search for gardening if you enter Garden instead of garden). This is the only case where character case should make a difference for a RCL search. You can also disable stem expansion or change the stemming language in the preferences.

Finding related documents.

Selecting the Find similar documents entry in the result list paragraph right-click menu will select a set of “interesting” terms from the current result, and insert them into the simple search entry field. You can then possibly edit the list and start a search to find documents which may be apparented to the current result.

File names.

File names are added as terms during indexing, and you can specify them as ordinary terms in normal search fields (RCL used to index all directories in the file path as terms. This has been abandoned as it did not seem really useful). Alternatively, you can use the specific file name search which will only look for file names, and may be faster than the generic search especially when using wildcards.

Working with phrases and proximity

Phrases and Proximity searches.

A phrase can be looked for by enclosing it in double quotes. Example: "user manual" will look only for occurrences of user immediately followed by manual. You can use the This phrase field of the advanced search dialog to the same effect. Phrases can be entered along simple terms in all simple or advanced search entry fields (except This exact phrase).

AutoPhrases.

This option can be set in the preferences dialog. If it is set, a phrase will be automatically built and added to simple searches when looking for Any terms. This will not change radically the results, but will give a relevance boost to the results where the search terms appear as a phrase. Ie: searching for virtual reality will still find all documents where either virtual or reality or both appear, but those which contain ``virtual

reality`` should appear sooner in the list.

Phrase searches can strongly slow down a query if most of the terms in the phrase are common. This is why the autophrase option is off by default for RCL versions before 1.17. As of version 1.17, autophrase is on by default, but very common terms will be removed from the constructed phrase. The removal threshold can be adjusted from the search preferences.

Phrases and abbreviations.

As of RCL version 1.17, dotted abbreviations like I.B.M. are also automatically indexed as a word without the dots: IBM. Searching for the word inside a phrase (ie: "the IBM company") will only match the dotted abrreviation if you increase the phrase slack (using the advanced search panel control, or the o query language modifier). Literal occurences of the word will be matched normally.

Others

Using fields.

You can use the query language and field specifications to only search certain parts of documents. This can be especially helpful with email, for example only searching emails from a specific originator: search tips from:helpfulgui

Ajusting the result table columns.

When displaying results in table mode, you can use a right click on the table headers to activate a pop-up menu which will let you adjust what columns are displayed. You can drag the column headers to adjust their order. You can click them to sort by the field displayed in the column. You can also save the result list in CSV format.

Changing the GUI geometry.

It is possible to configure the GUI in wide form factor by dragging the toolbars to one of the sides (their location is remembered between sessions), and moving the category filters to a menu (can be set in the Preferences > GUI configuration > User interface panel).

Query explanation.

You can get an exact description of what the query looked for, including stem expansion, and Boolean operators used, by clicking on the result list header.

Advanced search history.

As of RCL 1.18, you can display any of the last 100 complex searches performed by using the up and down arrow keys while the advanced search panel is active.

Browsing the result list inside a preview window.

Entering Shift-Down or Shift-Up (Shift + an arrow key) in a preview window will display the next or the previous document from the result list. Any secondary search currently active will be executed on the new document.

Scrolling the result list from the keyboard.

You can use PageUp and PageDown to scroll the result list, Shift+Home to go back to the first page. These work even while the focus is in the search entry.

Result table: moving the focus to the table.

You can use Ctrl-r to move the focus from the search entry to the table, and then use the arrow keys to change the current row. Ctrl-Shift-s returns to the search.

Result table: open / preview.

With the focus in the result table, you can use Ctrl-o to open the document from the current row, Ctrl-Shift-o to open the document and close recoll, Ctrl-d to preview the document.

Editing a new search while the focus is not in the search entry.

You can use the Ctrl-Shift-S shortcut to return the cursor to the search entry (and select the current search text), while the focus is anywhere in the main window.

Forced opening of a preview window.

You can use Shift+Click on a result list Preview link to force the creation of a preview window instead of a new tab in the existing one.

Closing previews.

Entering Ctrl-W in a tab will close it (and, for the last tab, close the preview window). Entering Esc will close the preview window and all its tabs.

Printing previews.

Entering Ctrl-P in a preview window will print the currently displayed text.

Quitting.

Entering Ctrl-Q almost anywhere will close the application.

Saving and restoring queries (1.21 and later)

Both simple and advanced query dialogs save recent history, but the amount is limited: old queries will eventually be forgotten. Also, important queries may be difficult to find among others. This is why both types of queries can also be explicitely saved to files, from the GUI menus: File > Save last query / Load last query

The default location for saved queries is a subdirectory of the current configuration directory, but saved queries are ordinary files and can be written or moved anywhere.

Some of the saved query parameters are part of the preferences (e.g. autophrase or the active external indexes), and may differ when the query is loaded from the time it was saved. In this case, RCL will warn of the differences, but will not change the user preferences.

Customizing the search interface

You can customize some aspects of the search interface by using the GUI configuration entry in the Preferences menu.

There are several tabs in the dialog, dealing with the interface itself, the parameters used for searching and returning results, and what indexes are searched.

User interface parameters:.

  • Highlight color for query terms: Terms from the user query are highlighted in the result list samples and the preview window. The color can be chosen here. Any Qt color string should work (ie red, #ff0000). The default is blue.

  • Style sheet: The name of a Qt style sheet text file which is applied to the whole Recoll application on startup. The default value is empty, but there is a skeleton style sheet (recoll.qss) inside the /usr/share/recoll/examples directory. Using a style sheet, you can change most recoll graphical parameters: colors, fonts, etc. See the sample file for a few simple examples.

    You should be aware that parameters (e.g.: the background color) set inside the RCL GUI style sheet will override global system preferences, with possible strange side effects: for example if you set the foreground to a light color and the background to a dark one in the desktop preferences, but only the background is set inside the RCL style sheet, and it is light too, then text will appear light-on-light inside the RCL GUI.

  • Maximum text size highlighted for preview Inserting highlights on search term inside the text before inserting it in the preview window involves quite a lot of processing, and can be disabled over the given text size to speed up loading.

  • Prefer HTML to plain text for preview if set, Recoll will display HTML as such inside the preview window. If this causes problems with the Qt HTML display, you can uncheck it to display the plain text version instead.

  • Activate links in preview if set, Recoll will turn HTTP links found inside plain text into proper HTML anchors, and clicking a link inside a preview window will start the default browser on the link target.

  • Plain text to HTML line style: when displaying plain text inside the preview window, RCL tries to preserve some of the original text line breaks and indentation. It can either use PRE HTML tags, which will well preserve the indentation but will force horizontal scrolling for long lines, or use BR tags to break at the original line breaks, which will let the editor introduce other line breaks according to the window width, but will lose some of the original indentation. The third option has been available in recent releases and is probably now the best one: use PRE tags with line wrapping.

  • Choose editor application: this opens a dialog which allows you to select the application to be used to open each MIME type. The default is to use the xdg-open utility, but you can use this dialog to override it, setting exceptions for MIME types that will still be opened according to RCL preferences. This is useful for passing parameters like page numbers or search strings to applications that support them (e.g. evince). This cannot be done with xdg-open which only supports passing one parameter.

  • Disable Qt autocompletion in search entry: this will disable the completion popup. Il will only appear, and display the full history, either if you enter only white space in the search area, or if you click the clock button on the right of the area.

  • Document filter choice style: this will let you choose if the document categories are displayed as a list or a set of buttons, or a menu.

  • Start with simple search mode: this lets you choose the value of the simple search type on program startup. Either a fixed value (e.g. Query Language, or the value in use when the program last exited.

  • Start with advanced search dialog open: If you use this dialog frequently, checking the entries will get it to open when recoll starts.

  • Remember sort activation state if set, Recoll will remember the sort tool stat between invocations. It normally starts with sorting disabled.

Result list parameters:.

  • Number of results in a result page
  • Result list font: There is quite a lot of information shown in the result list, and you may want to customize the font and/or font size. The rest of the fonts used by RCL are determined by your generic Qt config (try the qtconfig command).
  • Edit result list paragraph format string: allows you to change the presentation of each result list entry. See the result list customisation section.
  • Edit result page HTML header insert: allows you to define text inserted at the end of the result page HTML header. More detail in the result list customisation section.
  • Date format: allows specifying the format used for displaying dates inside the result list. This should be specified as an strftime() string (man strftime).
  • Abstract snippet separator: for synthetic abstracts built from index data, which are usually made of several snippets from different parts of the document, this defines the snippet separator, an ellipsis by default.

Search parameters:.

  • Hide duplicate results: decides if result list entries are shown for identical documents found in different places.

  • Stemming language: stemming obviously depends on the document’s language. This listbox will let you chose among the stemming databases which were built during indexing (this is set in the main configuration file), or later added with ``recollindex

    -s`` (See the recollindex manual). Stemming languages

    which are dynamically added will be deleted at the next indexing pass unless they are also added in the configuration file.

  • Automatically add phrase to simple searches: a phrase will be automatically built and added to simple searches when looking for ``Any

    terms``. This will give a relevance boost to the

    results where the search terms appear as a phrase (consecutive and in order).

  • Autophrase term frequency threshold percentage: very frequent terms should not be included in automatic phrase searches for performance reasons. The parameter defines the cutoff percentage (percentage of the documents where the term appears).

  • Replace abstracts from documents: this decides if we should synthesize and display an abstract in place of an explicit abstract found within the document itself.

  • Dynamically build abstracts: this decides if RCL tries to build document abstracts (lists of snippets) when displaying the result list. Abstracts are constructed by taking context from the document information, around the search terms.

  • Synthetic abstract size: adjust to taste...

  • Synthetic abstract context words: how many words should be displayed around each term occurrence.

  • Query language magic file name suffixes: a list of words which automatically get turned into ext:xxx file name suffix clauses when starting a query language query (ie: ``doc xls

    xlsx...``). This will save some typing for people who

    use file types a lot when querying.

External indexes:.

This panel will let you browse for additional indexes that you may want to search. External indexes are designated by their database directory (ie: /home/someothergui/.recoll/xapiandb, /usr/local/recollglobal/xapiandb).

Once entered, the indexes will appear in the External indexes list, and you can chose which ones you want to use at any moment by checking or unchecking their entries.

Your main database (the one the current configuration indexes to), is always implicitly active. If this is not desirable, you can set up your configuration so that it indexes, for example, an empty directory. An alternative indexer may also need to implement a way of purging the index from stale data,

The result list format

Newer versions of Recoll (from 1.17) normally use WebKit HTML widgets for the result list and the snippets window (this may be disabled at build time). Total customisation is possible with full support for CSS and Javascript. Conversely, there are limits to what you can do with the older Qt QTextBrowser, but still, it is possible to decide what data each result will contain, and how it will be displayed.

The result list presentation can be exhaustively customized by adjusting two elements:

  • The paragraph format
  • HTML code inside the header section. For versions 1.21 and later, this is also used for the snippets window

The paragraph format and the header fragment can be edited from the Result list tab of the GUI configuration.

The header fragment is used both for the result list and the snippets window. The snippets list is a table and has a snippets class attribute. Each paragraph in the result list is a table, with class respar, but this can be changed by editing the paragraph format.

There are a few examples on the page about customising the result list on the RCL web site.

The paragraph format

This is an arbitrary HTML string where the following printf-like % substitutions will be performed:

  • %A.

    Abstract

  • %D.

    Date

  • %I.

    Icon image name. This is normally determined from the MIME type. The associations are defined inside the `mimeconf configuration file <#RCL.INSTALL.CONFIG.MIMECONF>`__. If a thumbnail for the file is found at the standard Freedesktop location, this will be displayed instead.

  • %K.

    Keywords (if any)

  • %L.

    Precooked Preview, Edit, and possibly Snippets links

  • %M.

    MIME type

  • %N.

    result Number inside the result page

  • %P.

    Parent folder Url. In the case of an embedded document, this is the parent folder for the top level container file.

  • %R.

    Relevance percentage

  • %S.

    Size information

  • %T.

    Title or Filename if not set.

  • %t.

    Title or empty.

  • %(filename).

    File name.

  • %U.

    Url

The format of the Preview, Edit, and Snippets links is <a href="P%N">, <a href="E%N"> and <a href="A%N"> where docnum (%N) expands to the document number inside the result page).

A link target defined as "F%N" will open the document corresponding to the %P parent folder expansion, usually creating a file manager window on the folder where the container file resides. E.g.:

<a href="F%N">%P</a>

A link target defined as R%N|scriptname will run the corresponding script on the result file (if the document is embedded, the script will be started on the top-level parent). See the section about defining scripts.

In addition to the predefined values above, all strings like %(fieldname) will be replaced by the value of the field named fieldname for this document. Only stored fields can be accessed in this way, the value of indexed but not stored fields is not known at this point in the search process (see field configuration). There are currently very few fields stored by default, apart from the values above (only author and filename), so this feature will need some custom local configuration to be useful. An example candidate would be the recipient field which is generated by the message input handlers.

The default value for the paragraph format string is:

"<table class=\"respar\">\n"
"<tr>\n"
"<td><a href='%U'><img src='%I' width='64'></a></td>\n"
"<td>%L &nbsp;<i>%S</i> &nbsp;&nbsp;<b>%T</b><br>\n"
"<span style='white-space:nowrap'><i>%M</i>&nbsp;%D</span>&nbsp;&nbsp;&nbsp; <i>%U</i>&nbsp;%i<br>\n"
"%A %K</td>\n"
"</tr></table>\n"

You may, for example, try the following for a more web-like experience:

<u><b><a href="P%N">%T</a></b></u><br>
%A<font color=#008000>%U - %S</font> - %L

Note that the P%N link in the above paragraph makes the title a preview link. Or the clean looking:

<img src="%I" align="left">%L <font color="#900000">%R</font>
&nbsp;&nbsp;<b>%T&</b><br>%S&nbsp;
<font color="#808080"><i>%U</i></font>
<table bgcolor="#e0e0e0">
<tr><td><div>%A</div></td></tr>
</table>%K

These samples, and some others are on the web site, with pictures to show how they look.

It is also possible to define the value of the snippet separator inside the abstract section.

Searching with the KDE KIO slave

What’s this

The RCL KIO slave allows performing a RCL search by entering an appropriate URL in a KDE open dialog, or with an HTML-based interface displayed in Konqueror.

The HTML-based interface is similar to the Qt-based interface, but slightly less powerful for now. Its advantage is that you can perform your search while staying fully within the KDE framework: drag and drop from the result list works normally and you have your normal choice of applications for opening files.

The alternative interface uses a directory view of search results. Due to limitations in the current KIO slave interface, it is currently not obviously useful (to me).

The interface is described in more detail inside a help file which you can access by entering recoll:/ inside the konqueror URL line (this works only if the recoll KIO slave has been previously installed).

The instructions for building this module are located in the source tree. See: kde/kio/recoll/00README.txt. Some Linux distributions do package the kio-recoll module, so check before diving into the build process, maybe it’s already out there ready for one-click installation.

Searchable documents

As a sample application, the RCL KIO slave could allow preparing a set of HTML documents (for example a manual) so that they become their own search interface inside konqueror.

This can be done by either explicitly inserting <a href="recoll://..."> links around some document areas, or automatically by adding a very small javascript program to the documents, like the following example, which would initiate a search by double-clicking any term:

<script language="JavaScript">
        function recollsearch() {
        var t = document.getSelection();
        window.location.href = 'recoll://search/query?qtp=a&p=0&q=' +
        encodeURIComponent(t);
        }
        </script>
        ....
        <body ondblclick="recollsearch()">

Searching on the command line

There are several ways to obtain search results as a text stream, without a graphical interface:

  • By passing option -t to the recoll program, or by calling it as recollq (through a link).
  • By using the recollq program.
  • By writing a custom Python program, using the Recoll Python API.

The first two methods work in the same way and accept/need the same arguments (except for the additional -t to recoll). The query to be executed is specified as command line arguments.

recollq is not built by default. You can use the Makefile in the query directory to build it. This is a very simple program, and if you can program a little c++, you may find it useful to taylor its output format to your needs. Not that recollq is only really useful on systems where the Qt libraries (or even the X11 ones) are not available. Otherwise, just use ``recoll

-t``, which takes the exact same parameters and options which are

described for recollq

recollq has a man page (not installed by default, look in the doc/man directory). The Usage string is as follows:

recollq: usage:
-P: Show the date span for all the documents present in the index
[-o|-a|-f] [-q] <query string>
Runs a recoll query and displays result lines.
Default: will interpret the argument(s) as a xesam query string
query may be like:
implicit AND, Exclusion, field spec:    t1 -t2 title:t3
OR has priority: t1 OR t2 t3 OR t4 means (t1 OR t2) AND (t3 OR t4)
Phrase: "t1 t2" (needs additional quoting on cmd line)
-o Emulate the GUI simple search in ANY TERM mode
-a Emulate the GUI simple search in ALL TERMS mode
-f Emulate the GUI simple search in filename mode
-q is just ignored (compatibility with the recoll GUI command line)
Common options:
-c <configdir> : specify config directory, overriding $RECOLL_CONFDIR
-d also dump file contents
-n [first-]<cnt> define the result slice. The default value for [first]
is 0. Without the option, the default max count is 2000.
Use n=0 for no limit
-b : basic. Just output urls, no mime types or titles
-Q : no result lines, just the processed query and result count
-m : dump the whole document meta[] array for each result
-A : output the document abstracts
-S fld : sort by field <fld>
-s stemlang : set stemming language to use (must exist in index...)
Use -s "" to turn off stem expansion
-D : sort descending
-i <dbdir> : additional index, several can be given
-e use url encoding (%xx) for urls
-F <field name list> : output exactly these fields for each result.
The field values are encoded in base64, output in one line and
separated by one space character. This is the recommended format
for use by other programs. Use a normal query with option -m to
see the field names.

Sample execution:

recollq 'ilur -nautique mime:text/html'
      Recoll query: ((((ilur:(wqf=11) OR ilurs) AND_NOT (nautique:(wqf=11)
      OR nautiques OR nautiqu OR nautiquement)) FILTER Ttext/html))
      4 results
      text/html       [file:///Users/uncrypted-dockes/projets/bateaux/ilur/comptes.html]      [comptes.html]  18593   bytes
      text/html       [file:///Users/uncrypted-dockes/projets/nautique/webnautique/articles/ilur1/index.html] [Constructio...
      text/html       [file:///Users/uncrypted-dockes/projets/pagepers/index.html]    [psxtcl/writemime/recoll]...
      text/html       [file:///Users/uncrypted-dockes/projets/bateaux/ilur/factEtCie/recu-chasse-maree....

Using Synonyms (1.22)

Term synonyms:.

there are a number of ways to use term synonyms for searching text:

  • At index creation time, they can be used to alter the indexed terms, either increasing or decreasing their number, by expanding the original terms to all synonyms, or by reducing all synonym terms to a canonical one.
  • At query time, they can be used to match texts containing terms which are synonyms of the ones specified by the user, either by expanding the query for all synonyms, or by reducing the user entry to canonical terms (the latter only works if the corresponding processing has been performed while creating the index).

RCL only uses synonyms at query time. A user query term which part of a synonym group will be optionally expanded into an OR query for all terms in the group.

Synonym groups are defined inside ordinary text files. Each line in the file defines a group.

Example:

hi hello "good morning"

# not sure about "au revoir" though. Is this english ?
bye goodbye "see you" \
"au revoir"

As usual, lines beginning with a # are comments, empty lines are ignored, and lines can be continued by ending them with a backslash.

Multi-word synonyms are supported, but be aware that these will generate phrase queries, which may degrade performance and will disable stemming expansion for the phrase terms.

The synonyms file can be specified in the Search parameters tab of the GUI configuration Preferences menu entry, or as an option for command-line searches.

Once the file is defined, the use of synonyms can be enabled or disabled directly from the Preferences menu.

The synonyms are searched for matches with user terms after the latter are stem-expanded, but the contents of the synonyms file itself is not subjected to stem expansion. This means that a match will not be found if the form present in the synonyms file is not present anywhere in the document set.

The synonyms function is probably not going to help you find your letters to Mr. Smith. It is best used for domain-specific searches. For example, it was initially suggested by a user performing searches among historical documents: the synonyms file would contains nicknames and aliases for each of the persons of interest.

Path translations

In some cases, the document paths stored inside the index do not match the actual ones, so that document previews and accesses will fail. This can occur in a number of circumstances:

  • When using multiple indexes it is a relatively common occurrence that some will actually reside on a remote volume, for exemple mounted via NFS. In this case, the paths used to access the documents on the local machine are not necessarily the same than the ones used while indexing on the remote machine. For example, /home/me may have been used as a topdirs elements while indexing, but the directory might be mounted as /net/server/home/me on the local machine.
  • The case may also occur with removable disks. It is perfectly possible to configure an index to live with the documents on the removable disk, but it may happen that the disk is not mounted at the same place so that the documents paths from the index are invalid.
  • As a last exemple, one could imagine that a big directory has been moved, but that it is currently inconvenient to run the indexer.

RCL has a facility for rewriting access paths when extracting the data from the index. The translations can be defined for the main index and for any additional query index.

The path translation facility will be useful whenever the documents paths seen by the indexer are not the same as the ones which should be used at query time.

In the above NFS example, RCL could be instructed to rewrite any file:///home/me URL from the index to file:///net/server/home/me, allowing accesses from the client.

The translations are defined in the `ptrans <#RCL.INSTALL.CONFIG.PTRANS>`__ configuration file, which can be edited by hand or from the GUI external indexes configuration dialog: Preferences > External index dialog, then click the Paths translations button on the right below the index list.

Note

Due to a current bug, the GUI must be restarted after changing the ptrans values (even when they were changed from the GUI).

The query language

The query language processor is activated in the GUI simple search entry when the search mode selector is set to Query Language. It can also be used with the KIO slave or the command line search. It broadly has the same capabilities as the complex search interface in the GUI.

The language was based on the now defunct Xesam user search language specification.

If the results of a query language search puzzle you and you doubt what has been actually searched for, you can use the GUI Show Query link at the top of the result list to check the exact query which was finally executed by Xapian.

Here follows a sample request that we are going to explain:

author:"john doe" Beatles OR Lennon Live OR Unplugged -potatoes

This would search for all documents with John Doe appearing as a phrase in the author field (exactly what this is would depend on the document type, ie: the From: header, for an email message), and containing either beatles or lennon and either live or unplugged but not potatoes (in any part of the document).

An element is composed of an optional field specification, and a value, separated by a colon (the field separator is the last colon in the element). Examples: Eugenie, author:balzac, dc:title:grandet dc:title:”eugenie grandet”

The colon, if present, means “contains”. Xesam defines other relations, which are mostly unsupported for now (except in special cases, described further down).

All elements in the search entry are normally combined with an implicit AND. It is possible to specify that elements be OR’ed instead, as in Beatles OR Lennon. The OR must be entered literally (capitals), and it has priority over the AND associations: word1 word2 OR word3 means word1 AND (word2 OR word3) not (word1 AND word2) OR word3.

RCL versions 1.21 and later, allow using parentheses to group elements, which will sometimes make things clearer, and may allow expressing combinations which would have been difficult otherwise.

An element preceded by a - specifies a term that should not appear.

As usual, words inside quotes define a phrase (the order of words is significant), so that title:”prejudice pride” is not the same as title:prejudice title:pride, and is unlikely to find a result.

Words inside phrases and capitalized words are not stem-expanded. Wildcards may be used anywhere inside a term. Specifying a wild-card on the left of a term can produce a very slow search (or even an incorrect one if the expansion is truncated because of excessive size). Also see More about wildcards.

To save you some typing, recent RCL versions (1.20 and later) interpret a comma-separated list of terms as an AND list inside the field. Use slash characters (‘/’) for an OR list. No white space is allowed. So

author:john,lennon

will search for documents with john and lennon inside the author field (in any order), and

author:john/ringo

would search for john or ringo.

Modifiers can be set on a double-quote value, for example to specify a proximity search (unordered). See the modifier section. No space must separate the final double-quote and the modifiers value, e.g. “two one”po10

RCL currently manages the following default fields:

  • title, subject or caption are synonyms which specify data to be searched for in the document title or subject.
  • author or from for searching the documents originators.
  • recipient or to for searching the documents recipients.
  • keyword for searching the document-specified keywords (few documents actually have any).
  • filename for the document’s file name. This is not necessarily set for all documents: internal documents contained inside a compound one (for example an EPUB section) do not inherit the container file name any more, this was replaced by an explicit field (see next). Sub-documents can still have a specific filename, if it is implied by the document format, for example the attachment file name for an email attachment.
  • containerfilename. This is set for all documents, both top-level and contained sub-documents, and is always the name of the filesystem directory entry which contains the data. The terms from this field can only be matched by an explicit field specification (as opposed to terms from filename which are also indexed as general document content). This avoids getting matches for all the sub-documents when searching for the container file name.
  • ext specifies the file name extension (Ex: ext:html)

RCL 1.20 and later have a way to specify aliases for the field names, which will save typing, for example by aliasing filename to fn or containerfilename to cfn. See the section about the ``fields` file <#RCL.INSTALL.CONFIG.FIELDS>`__

The document input handlers used while indexing have the possibility to create other fields with arbitrary names, and aliases may be defined in the configuration, so that the exact field search possibilities may be different for you if someone took care of the customisation.

The field syntax also supports a few field-like, but special, criteria:

  • dir for filtering the results on file location (Ex: dir:/home/me/somedir). -dir also works to find results not in the specified directory (release >= 1.15.8). Tilde expansion will be performed as usual (except for a bug in versions 1.19 to 1.19.11p1). Wildcards will be expanded, but please have a look at an important limitation of wildcards in path filters.

    Relative paths also make sense, for example, dir:share/doc would match either /usr/share/doc or /usr/local/share/doc

    Several dir clauses can be specified, both positive and negative. For example the following makes sense:

    dir:recoll dir:src -dir:utils -dir:common

    This would select results which have both recoll and src in the path (in any order), and which have not either utils or common.

    You can also use OR conjunctions with dir: clauses.

    A special aspect of dir clauses is that the values in the index are not transcoded to UTF-8, and never lower-cased or unaccented, but stored as binary. This means that you need to enter the values in the exact lower or upper case, and that searches for names with diacritics may sometimes be impossible because of character set conversion issues. Non-ASCII UNIX file paths are an unending source of trouble and are best avoided.

    You need to use double-quotes around the path value if it contains space characters.

  • size for filtering the results on file size. Example: size<10000. You can use <, > or = as operators. You can specify a range like the following: size>100 size<1000. The usual k/K, m/M, g/G, t/T can be used as (decimal) multipliers. Ex: size>1k to search for files bigger than 1000 bytes.

  • date for searching or filtering on dates. The syntax for the argument is based on the ISO8601 standard for dates and time intervals. Only dates are supported, no times. The general syntax is 2 elements separated by a / character. Each element can be a date or a period of time. Periods are specified as PnYnMnD. The n numbers are the respective numbers of years, months or days, any of which may be missing. Dates are specified as YYYY-MM-DD. The days and months parts may be missing. If the / is present but an element is missing, the missing element is interpreted as the lowest or highest date in the index. Examples:

    • 2001-03-01/2002-05-01 the basic syntax for an interval of dates.
    • 2001-03-01/P1Y2M the same specified with a period.
    • 2001/ from the beginning of 2001 to the latest date in the index.
    • 2001 the whole year of 2001
    • P2D/ means 2 days ago up to now if there are no documents with dates in the future.
    • /2003 all documents from 2003 or older.

    Periods can also be specified with small letters (ie: p2y).

  • mime or format for specifying the MIME type. These clauses are processed besides the normal Boolean logic of the search. Multiple values will be OR’ed (instead of the normal AND). You can specify types to be excluded, with the usual -, and use wildcards. Example: mime:text/* -mime:text/plain Specifying an explicit boolean operator before a mime specification is not supported and will produce strange results.

  • type or rclcat for specifying the category (as in text/media/presentation/etc.). The classification of MIME types in categories is defined in the RCL configuration (mimeconf), and can be modified or extended. The default category names are those which permit filtering results in the main GUI screen. Categories are OR’ed like MIME types above, and can be negated with -.

    Note

    mime, rclcat, size and date criteria always affect the whole query (they are applied as a final filter), even if set with other terms inside a parenthese.

    Note

    mime (or the equivalent rclcat) is the only field with an OR default. You do need to use OR with ext terms for example.

Range clauses

RCL 1.24 and later support range clauses on fields which have been configured to support it. No default field uses them currently, so this paragraph is only interesting if you modified the fields configuration and possibly use a custom input handler.

A range clause looks like one of the following:

myfield:small..big
myfield:small..
myfield:..big

The nature of the clause is indicated by the two dots .., and the effect is to filter the results for which the myfield value is in the possibly open-ended interval.

See the section about the `fields configuration file <#RCL.INSTALL.CONFIG.FIELDS>`__ for the details of configuring a field for range searches (list them in the [values] section).

Modifiers

Some characters are recognized as search modifiers when found immediately after the closing double quote of a phrase, as in "some term"modifierchars. The actual “phrase” can be a single term of course. Supported modifiers:

  • l can be used to turn off stemming (mostly makes sense with p because stemming is off by default for phrases).
  • s can be used to turn off synonym expansion, if a synonyms file is in place (only for RCL 1.22 and later).
  • o can be used to specify a “slack” for phrase and proximity searches: the number of additional terms that may be found between the specified ones. If o is followed by an integer number, this is the slack, else the default is 10.
  • p can be used to turn the default phrase search into a proximity one (unordered). Example: "order any in"p
  • C will turn on case sensitivity (if the index supports it).
  • D will turn on diacritics sensitivity (if the index supports it).
  • A weight can be specified for a query element by specifying a decimal value at the start of the modifiers. Example: "Important"2.5.

Search case and diacritics sensitivity

For RCL versions 1.18 and later, and when working with a raw index (not the default), searches can be sensitive to character case and diacritics. How this happens is controlled by configuration variables and what search data is entered.

The general default is that searches entered without upper-case or accented characters are insensitive to case and diacritics. An entry of resume will match any of Resume, RESUME, résumé, Résumé etc.

Two configuration variables can automate switching on sensitivity (they were documented but actually did nothing until RCL 1.22):

autodiacsens
If this is set, search sensitivity to diacritics will be turned on as soon as an accented character exists in a search term. When the variable is set to true, resume will start a diacritics-unsensitive search, but résumé will be matched exactly. The default value is false.
autocasesens
If this is set, search sensitivity to character case will be turned on as soon as an upper-case character exists in a search term except for the first one. When the variable is set to true, us or Us will start a diacritics-unsensitive search, but US will be matched exactly. The default value is true (contrary to autodiacsens).

As in the past, capitalizing the first letter of a word will turn off its stem expansion and have no effect on case-sensitivity.

You can also explicitely activate case and diacritics sensitivity by using modifiers with the query language. C will make the term case-sensitive, and D will make it diacritics-sensitive. Examples:

"us"C

will search for the term us exactly (Us will not be a match).

"resume"D

will search for the term resume exactly (résumé will not be a match).

When either case or diacritics sensitivity is activated, stem expansion is turned off. Having both does not make much sense.

Anchored searches and wildcards

Some special characters are interpreted by RCL in search strings to expand or specialize the search. Wildcards expand a root term in controlled ways. Anchor characters can restrict a search to succeed only if the match is found at or near the beginning of the document or one of its fields.

More about wildcards

All words entered in RCL search fields will be processed for wildcard expansion before the request is finally executed.

The wildcard characters are:

  • * which matches 0 or more characters.
  • ? which matches a single character.
  • [] which allow defining sets of characters to be matched (ex: [abc] matches a single character which may be ‘a’ or ‘b’ or ‘c’, [0-9] matches any number.

You should be aware of a few things when using wildcards.

  • Using a wildcard character at the beginning of a word can make for a slow search because RCL will have to scan the whole index term list to find the matches. However, this is much less a problem for field searches, and queries like author:*@domain.com can sometimes be very useful.
  • For RCL version 18 only, when working with a raw index (preserving character case and diacritics), the literal part of a wildcard expression will be matched exactly for case and diacritics. This is not true any more for versions 19 and later.
  • Using a * at the end of a word can produce more matches than you would think, and strange search results. You can use the term explorer tool to check what completions exist for a given term. You can also see exactly what search was performed by clicking on the link at the top of the result list. In general, for natural language terms, stem expansion will produce better results than an ending * (stem expansion is turned off when any wildcard character appears in the term).
Wildcards and path filtering

Due to the way that RCL processes wildcards inside dir path filtering clauses, they will have a multiplicative effect on the query size. A clause containg wildcards in several paths elements, like, for example, dir:/home/me/*/*/docdir, will almost certainly fail if your indexed tree is of any realistic size.

Depending on the case, you may be able to work around the issue by specifying the paths elements more narrowly, with a constant prefix, or by using 2 separate dir: clauses instead of multiple wildcards, as in dir:/home/me dir:docdir. The latter query is not equivalent to the initial one because it does not specify a number of directory levels, but that’s the best we can do (and it may be actually more useful in some cases).

Anchored searches

Two characters are used to specify that a search hit should occur at the beginning or at the end of the text. ^ at the beginning of a term or phrase constrains the search to happen at the start, $ at the end force it to happen at the end.

As this function is implemented as a phrase search it is possible to specify a maximum distance at which the hit should occur, either through the controls of the advanced search panel, or using the query language, for example, as in:

"^someterm"o10

which would force someterm to be found within 10 terms of the start of the text. This can be combined with a field search as in somefield:"^someterm"o10 or somefield:someterm$.

This feature can also be used with an actual phrase search, but in this case, the distance applies to the whole phrase and anchor, so that, for example, ``bla bla my unexpected

term`` at the beginning of the text would be a match for

"^my term"o5.

Anchored searches can be very useful for searches inside somewhat structured documents like scientific articles, in case explicit metadata has not been supplied (a most frequent case), for example for looking for matches inside the abstract or the list of authors (which occur at the top of the document).

Desktop integration

Being independant of the desktop type has its drawbacks: RCL desktop integration is minimal. However there are a few tools available:

Here follow a few other things that may help.

Hotkeying recoll

It is surprisingly convenient to be able to show or hide the RCL GUI with a single keystroke. Recoll comes with a small Python script, based on the libwnck window manager interface library, which will allow you to do just this. The detailed instructions are on this wiki page.

The KDE Kicker Recoll applet

This is probably obsolete now. Anyway:

The RCL source tree contains the source code to the recoll_applet, a small application derived from the find_applet. This can be used to add a small RCL launcher to the KDE panel.

The applet is not automatically built with the main RCL programs, nor is it included with the main source distribution (because the KDE build boilerplate makes it relatively big). You can download its source from the recoll.org download page. Use the omnipotent configure;make;make install incantation to build and install.

You can then add the applet to the panel by right-clicking the panel and choosing the Add applet entry.

The recoll_applet has a small text window where you can type a RCL query (in query language form), and an icon which can be used to restrict the search to certain types of files. It is quite primitive, and launches a new recoll GUI instance every time (even if it is already running). You may find it useful anyway.

Removable volumes

RCL used to have no support for indexing removable volumes (portable disks, USB keys, etc.). Recent versions have improved the situation and support indexing removable volumes in two different ways:

  • By storing a volume index on the volume itself (RCL 1.24).
  • By indexing the volume in the main, fixed, index, and ensuring that the volume data is not purged if the indexing runs while the volume is mounted. (RCL 1.25.2).

Indexing removable volumes in the main index

As of version 1.25.2, RCL has a simple way to ensure that the index data for an absent volume will not be purged: the volume mount point must be a member of the topdirs list, and the mount directory must be empty (when the volume is not mounted). If recollindex finds that one of the topdirs is empty when starting up, any existing data for the tree will be preserved by the indexing pass (no purge for this area).

Self contained volumes

As of RCL 1.24, it has become easy to build self-contained datasets including a RCL configuration directory and index together with the indexed documents, and to move such a dataset around (for example copying it to an USB drive), without having to adjust the configuration for querying the index.

Note

This is a query-time feature only. The index must only be updated in its original location. If an update is necessary in a different location, the index must be reset.

To make a long story short, here follows a script to create a RCL configuration and index under a given directory (given as single parameter). The resulting data set (files + recoll directory) can later to be moved to a CDROM or thumb drive. Longer explanations come after the script.

#!/bin/sh

fatal()
{
    echo $*;exit 1
}
usage()
{
    fatal "Usage: init-recoll-volume.sh <top-directory>"
}

test $# = 1 || usage
topdir=$1
test -d "$topdir" || fatal $topdir should be a directory

confdir="$topdir/recoll-config"
test ! -d "$confdir" || fatal $confdir should not exist

mkdir "$confdir"
cd "$topdir"
topdir=`pwd`
cd "$confdir"
confdir=`pwd`

(echo topdirs = '"'$topdir'"'; \
 echo orgidxconfdir = $topdir/recoll-config) > "$confdir/recoll.conf"

recollindex -c "$confdir"

The examples below will assume that you have a dataset under /home/me/mydata/, with the index configuration and data stored inside /home/me/mydata/recoll-confdir.

In order to be able to run queries after the dataset has been moved, you must ensure the following:

  • The main configuration file must define the orgidxconfdir variable to be the original location of the configuration directory (orgidxconfdir=/home/me/mydata/recoll-confdir must be set inside /home/me/mydata/recoll-confdir/recoll.conf in the example above).
  • The configuration directory must exist with the documents, somewhere under the directory which will be moved. E.g. if you are moving /home/me/mydata around, the configuration directory must exist somewhere below this point, for example /home/me/mydata/recoll-confdir, or /home/me/mydata/sub/recoll-confdir.
  • You should keep the default locations for the index elements (they are relative to the configuration directory by default). Only the paths referring to the documents themselves (e.g. topdirs values) should be absolute (in general, they are only used when indexing anyway).

Only the first point needs an explicit user action, the RCL defaults are compatible with the second one, and the third is natural.

If, after the move, the configuration directory needs to be copied out of the dataset (for example because the thumb drive is too slow), you can set the curidxconfdir, variable inside the copied configuration to define the location of the moved one. For example if /home/me/mydata is now mounted onto /media/me/somelabel, but the configuration directory and index has been copied to /tmp/tempconfig, you would set curidxconfdir to /media/me/somelabel/recoll-confdir inside /tmp/tempconfig/recoll.conf. orgidxconfdir would still be /home/me/mydata/recoll-confdir in the original and the copy.

If you are regularly copying the configuration out of the dataset, it will be useful to write a script to automate the procedure. This can’t really be done inside RCL because there are probably many possible variants. One example would be to copy the configuration to make it writable, but keep the index data on the medium because it is too big - in this case, the script would also need to set dbdir in the copied configuration.

The same set of modifications (RCL 1.24) has also made it possible to run queries from a readonly configuration directory (with slightly reduced function of course, such as not recording the query history).

Programming interface

RCL has an Application Programming Interface, usable both for indexing and searching, currently accessible from the Python language.

Another less radical way to extend the application is to write input handlers for new types of documents.

The processing of metadata attributes for documents (fields) is highly configurable.

Writing a document input handler

Note

The small programs or pieces of code which handle the processing of the different document types for RCL used to be called filters, which is still reflected in the name of the directory which holds them and many configuration variables. They were named this way because one of their primary functions is to filter out the formatting directives and keep the text content. However these modules may have other behaviours, and the term input handler is now progressively substituted in the documentation. filter is still used in many places though.

RCL input handlers cooperate to translate from the multitude of input document formats, simple ones as opendocument, acrobat, or compound ones such as Zip or Email, into the final RCL indexing input format, which is plain text (in many cases the processing pipeline has an intermediary HTML step, which may be used for better previewing presentation). Most input handlers are executable programs or scripts. A few handlers are coded in C++ and live inside recollindex. This latter kind will not be described here.

There are currently (since version 1.13) two kinds of external executable input handlers:

  • Simple exec handlers run once and exit. They can be bare programs like antiword, or scripts using other programs. They are very simple to write, because they just need to print the converted document to the standard output. Their output can be plain text or HTML. HTML is usually preferred because it can store metadata fields and it allows preserving some of the formatting for the GUI preview. However, these handlers have limitations:
    • They can only process one document per file.
    • The output MIME type must be known and fixed.
    • The character encoding, if relevant, must be known and fixed (or possibly just depending on location).
  • Multiple execm handlers can process multiple files (sparing the process startup time which can be very significant), or multiple documents per file (e.g.: for archives or multi-chapter publications). They communicate with the indexer through a simple protocol, but are nevertheless a bit more complicated than the older kind. Most of the new handlers are written in Python (exception: rclimg which is written in Perl because exiftool has no real Python equivalent). The Python handlers use common modules to factor out the boilerplate, which can make them very simple in favorable cases. The subdocuments output by these handlers can be directly indexable (text or HTML), or they can be other simple or compound documents that will need to be processed by another handler.

In both cases, handlers deal with regular file system files, and can process either a single document, or a linear list of documents in each file. RCL is responsible for performing up to date checks, deal with more complex embedding and other upper level issues.

A simple handler returning a document in text/plain format, can transfer no metadata to the indexer. Generic metadata, like document size or modification date, will be gathered and stored by the indexer.

Handlers that produce text/html format can return an arbitrary amount of metadata inside HTML meta tags. These will be processed according to the directives found in the `fields configuration file <#RCL.PROGRAM.FIELDS>`__.

The handlers that can handle multiple documents per file return a single piece of data to identify each document inside the file. This piece of data, called an ipath will be sent back by RCL to extract the document at query time, for previewing, or for creating a temporary file to be opened by a viewer. These handlers can also return metadata either as HTML meta tags, or as named data through the communication protocol.

The following section describes the simple handlers, and the next one gives a few explanations about the execm ones. You could conceivably write a simple handler with only the elements in the manual. This will not be the case for the other ones, for which you will have to look at the code.

Simple input handlers

RCL simple handlers are usually shell-scripts, but this is in no way necessary. Extracting the text from the native format is the difficult part. Outputting the format expected by RCL is trivial. Happily enough, most document formats have translators or text extractors which can be called from the handler. In some cases the output of the translating program is completely appropriate, and no intermediate shell-script is needed.

Input handlers are called with a single argument which is the source file name. They should output the result to stdout.

When writing a handler, you should decide if it will output plain text or HTML. Plain text is simpler, but you will not be able to add metadata or vary the output character encoding (this will be defined in a configuration file). Additionally, some formatting may be easier to preserve when previewing HTML. Actually the deciding factor is metadata: RCL has a way to extract metadata from the HTML header and use it for field searches..

The RECOLL_FILTER_FORPREVIEW environment variable (values yes, no) tells the handler if the operation is for indexing or previewing. Some handlers use this to output a slightly different format, for example stripping uninteresting repeated keywords (ie: Subject: for email) when indexing. This is not essential.

You should look at one of the simple handlers, for example rclps for a starting point.

Don’t forget to make your handler executable before testing !

“Multiple” handlers

If you can program and want to write an execm handler, it should not be too difficult to make sense of one of the existing handlers.

The existing handlers differ in the amount of helper code which they are using:

  • rclimg is written in Perl and handles the execm protocol all by itself (showing how trivial it is).
  • All the Python handlers share at least the rclexecm.py module, which handles the communication. Have a look at, for example, rclzip for a handler which uses rclexecm.py directly.
  • Most Python handlers which process single-document files by executing another command are further abstracted by using the rclexec1.py module. See for example rclrtf.py for a simple one, or rcldoc.py for a slightly more complicated one (possibly executing several commands).
  • Handlers which extract text from an XML document by using an XSLT style sheet are now executed inside recollindex, with only the style sheet stored in the filters/ directory. These can use a single style sheet (e.g. abiword.xsl), or two sheets for the data and metadata (e.g. opendoc-body.xsl and opendoc-meta.xsl). The mimeconf configuration file defines how the sheets are used, have a look. Before the C++ import, the xsl-based handlers used a common module rclgenxslt.py, it is still around but unused. The handler for OpenXML presentations is still the Python version because the format did not fit with what the C++ code does. It would be a good base for another similar issue.

There is a sample trivial handler based on rclexecm.py, with many comments, not actually used by RCL. It would index a text file as one document per line. Look for rcltxtlines.py in the src/filters directory in the online RCL Git repository (the sample not in the distributed release at the moment).

You can also have a look at the slightly more complex rclzip which uses Zip file paths as identifiers (ipath).

execm handlers sometimes need to make a choice for the nature of the ipath elements that they use in communication with the indexer. Here are a few guidelines:

  • Use ASCII or UTF-8 (if the identifier is an integer print it, for example, like printf %d would do).
  • If at all possible, the data should make some kind of sense when printed to a log file to help with debugging.
  • RCL uses a colon (:) as a separator to store a complex path internally (for deeper embedding). Colons inside the ipath elements output by a handler will be escaped, but would be a bad choice as a handler-specific separator (mostly, again, for debugging issues).

In any case, the main goal is that it should be easy for the handler to extract the target document, given the file name and the ipath element.

execm handlers will also produce a document with a null ipath element. Depending on the type of document, this may have some associated data (e.g. the body of an email message), or none (typical for an archive file). If it is empty, this document will be useful anyway for some operations, as the parent of the actual data documents.

Telling RCL about the handler

There are two elements that link a file to the handler which should process it: the association of file to MIME type and the association of a MIME type with a handler.

The association of files to MIME types is mostly based on name suffixes. The types are defined inside the `mimemap file <#RCL.INSTALL.CONFIG.MIMEMAP>`__. Example:

.doc = application/msword

If no suffix association is found for the file name, RCL will try to execute a system command (typically file -i or xdg-mime) to determine a MIME type.

The second element is the association of MIME types to handlers in the `mimeconf file <#RCL.INSTALL.CONFIG.MIMECONF>`__. A sample will probably be better than a long explanation:

[index]
application/msword = exec antiword -t -i 1 -m UTF-8;\
mimetype = text/plain ; charset=utf-8

application/ogg = exec rclogg

text/rtf = exec unrtf --nopict --html; charset=iso-8859-1; mimetype=text/html

application/x-chm = execm rclchm

The fragment specifies that:

  • application/msword files are processed by executing the antiword program, which outputs text/plain encoded in utf-8.
  • application/ogg files are processed by the rclogg script, with default output type (text/html, with encoding specified in the header, or utf-8 by default).
  • text/rtf is processed by unrtf, which outputs text/html. The iso-8859-1 encoding is specified because it is not the utf-8 default, and not output by unrtf in the HTML header section.
  • application/x-chm is processed by a persistant handler. This is determined by the execm keyword.

Input handler output

Both the simple and persistent input handlers can return any MIME type to Recoll, which will further process the data according to the MIME configuration.

Most input filters filters produce either text/plain or text/html data. There are exceptions, for example, filters which process archive file (zip, tar, etc.) will usually return the documents as they are found, without processing them further.

There is nothing to say about text/plain output, except that its character encoding should be consistent with what is specified in the mimeconf file.

For filters producing HTML, the output could be very minimal like the following example:

<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
</head>
<body>
Some text content
</body>
</html>

You should take care to escape some characters inside the text by transforming them into appropriate entities. At the very minimum, “&” should be transformed into “&amp;”, “<” should be transformed into “&lt;”. This is not always properly done by external helper programs which output HTML, and of course never by those which output plain text.

When encapsulating plain text in an HTML body, the display of a preview may be improved by enclosing the text inside <pre> tags.

The character set needs to be specified in the header. It does not need to be UTF-8 (RCL will take care of translating it), but it must be accurate for good results.

RCL will process meta tags inside the header as possible document fields candidates. Documents fields can be processed by the indexer in different ways, for searching or displaying inside query results. This is described in a following section.

By default, the indexer will process the standard header fields if they are present: title, meta/description, and meta/keywords are both indexed and stored for query-time display.

A predefined non-standard meta tag will also be processed by RCL without further configuration: if a date tag is present and has the right format, it will be used as the document date (for display and sorting), in preference to the file modification date. The date format should be as follows:

<meta name="date" content="YYYY-mm-dd HH:MM:SS">
or
<meta name="date" content="YYYY-mm-ddTHH:MM:SS">

Example:

<meta name="date" content="2013-02-24 17:50:00">

Input handlers also have the possibility to “invent” field names. This should also be output as meta tags:

<meta name="somefield" content="Some textual data" />

You can embed HTML markup inside the content of custom fields, for improving the display inside result lists. In this case, add a (wildly non-standard) markup attribute to tell RCL that the value is HTML and should not be escaped for display.

<meta name="somefield" markup="html" content="Some <i>textual</i> data" />

As written above, the processing of fields is described in a further section.

Persistent filters can use another, probably simpler, method to produce metadata, by calling the setfield() helper method. This avoids the necessity to produce HTML, and any issue with HTML quoting. See, for example, rclaudio in RCL 1.23 and later for an example of handler which outputs text/plain and uses setfield() to produce metadata.

Page numbers

The indexer will interpret ^L characters in the handler output as indicating page breaks, and will record them. At query time, this allows starting a viewer on the right page for a hit or a snippet. Currently, only the PDF, Postscript and DVI handlers generate page breaks.

Field data processing

Fields are named pieces of information in or about documents, like title, author, abstract.

The field values for documents can appear in several ways during indexing: either output by input handlers as meta fields in the HTML header section, or extracted from file extended attributes, or added as attributes of the Doc object when using the API, or again synthetized internally by RCL.

The RCL query language allows searching for text in a specific field.

RCL defines a number of default fields. Additional ones can be output by handlers, and described in the fields configuration file.

Fields can be:

  • indexed, meaning that their terms are separately stored in inverted lists (with a specific prefix), and that a field-specific search is possible.
  • stored, meaning that their value is recorded in the index data record for the document, and can be returned and displayed with search results.

A field can be either or both indexed and stored. This and other aspects of fields handling is defined inside the fields configuration file.

Some fields may also designated as supporting range queries, meaning that the results may be selected for an interval of its values. See the configuration section for more details.

The sequence of events for field processing is as follows:

  • During indexing, recollindex scans all meta fields in HTML documents (most document types are transformed into HTML at some point). It compares the name for each element to the configuration defining what should be done with fields (the fields file)
  • If the name for the meta element matches one for a field that should be indexed, the contents are processed and the terms are entered into the index with the prefix defined in the fields file.
  • If the name for the meta element matches one for a field that should be stored, the content of the element is stored with the document data record, from which it can be extracted and displayed at query time.
  • At query time, if a field search is performed, the index prefix is computed and the match is only performed against appropriately prefixed terms in the index.
  • At query time, the field can be displayed inside the result list by using the appropriate directive in the definition of the result list paragraph format. All fields are displayed on the fields screen of the preview window (which you can reach through the right-click menu). This is independant of the fact that the search which produced the results used the field or not.

You can find more information in the section about the ``fields` file <#RCL.INSTALL.CONFIG.FIELDS>`__, or in comments inside the file.

You can also have a look at the example in the FAQs area, detailing how one could add a page count field to pdf documents for displaying inside result lists.

Python API

Introduction

The RCL Python programming interface can be used both for searching and for creating/updating an index. Bindings exist for Python2 and Python3.

The search interface is used in a number of active projects: the RCL Gnome Shell Search Provider, the RCL Web UI, and the upmpdcli UPnP Media Server, in addition to many small scripts.

The index update section of the API may be used to create and update RCL indexes on specific configurations (separate from the ones created by recollindex). The resulting databases can be queried alone, or in conjunction with regular ones, through the GUI or any of the query interfaces.

The search API is modeled along the Python database API specification. There were two major changes along RCL versions:

  • The basis for the RCL API changed from Python database API version 1.0 (RCL versions up to 1.18.1), to version 2.0 (RCL 1.18.2 and later).
  • The recoll module became a package (with an internal recoll module) as of RCL version 1.19, in order to add more functions. For existing code, this only changes the way the interface must be imported.

We will describe the new API and package structure here. A paragraph at the end of this section will explain a few differences and ways to write code compatible with both versions.

The recoll package now contains two modules:

  • The recoll module contains functions and classes used to query (or update) the index.
  • The rclextract module contains functions and classes used at query time to access document data.

There is a good chance that your system repository has packages for the Recoll Python API, sometimes in a package separate from the main one (maybe named something like python-recoll). Else refer to the Building from source chapter.

As an introduction, the following small sample will run a query and list the title and url for each of the results. It would work with RCL 1.19 and later. The python/samples source directory contains several examples of Python programming with RCL, exercising the extension more completely, and especially its data extraction features.

#!/usr/bin/env python

from recoll import recoll

db = recoll.connect()
query = db.query()
nres = query.execute("some query")
results = query.fetchmany(20)
for doc in results:
    print("%s %s" % (doc.url, doc.title))

You can also take a look at the source for the Recoll WebUI, the upmpdcli local media server, or the Gnome Shell Search Provider.

Interface elements

A few elements in the interface are specific and and need an explanation.

ipath
This data value (set as a field in the Doc object) is stored, along with the URL, but not indexed by RCL. Its contents are not interpreted by the index layer, and its use is up to the application. For example, the RCL file system indexer uses the ipath to store the part of the document access path internal to (possibly imbricated) container documents. ipath in this case is a vector of access elements (e.g, the first part could be a path inside a zip file to an archive member which happens to be an mbox file, the second element would be the message sequential number inside the mbox etc.). url and ipath are returned in every search result and define the access to the original document. ipath is empty for top-level document/files (e.g. a PDF document which is a filesystem file). The RCL GUI knows about the structure of the ipath values used by the filesystem indexer, and uses it for such functions as opening the parent of a given document.
udi
An udi (unique document identifier) identifies a document. Because of limitations inside the index engine, it is restricted in length (to 200 bytes), which is why a regular URI cannot be used. The structure and contents of the udi is defined by the application and opaque to the index engine. For example, the internal file system indexer uses the complete document path (file path + internal path), truncated to length, the suppressed part being replaced by a hash value. The udi is not explicit in the query interface (it is used “under the hood” by the rclextract module), but it is an explicit element of the update interface.
parent_udi
If this attribute is set on a document when entering it in the index, it designates its physical container document. In a multilevel hierarchy, this may not be the immediate parent. parent_udi is optional, but its use by an indexer may simplify index maintenance, as RCL will automatically delete all children defined by parent_udi == udi when the document designated by udi is destroyed. e.g. if a Zip archive contains entries which are themselves containers, like mbox files, all the subdocuments inside the Zip file (mbox, messages, message attachments, etc.) would have the same parent_udi, matching the udi for the Zip file, and all would be destroyed when the Zip file (identified by its udi) is removed from the index. The standard filesystem indexer uses parent_udi.
Stored and indexed fields
The `fields file <#RCL.INSTALL.CONFIG.FIELDS>`__ inside the RCL configuration defines which document fields are either indexed (searchable), stored (retrievable with search results), or both. Apart from a few standard/internal fields, only the stored fields are retrievable through the Python search interface.

Python search interface

The recoll module

The connect() function connects to one or several RCL index(es) and returns a Db object.

This call initializes the recoll module, and it should always be performed before any other call or object creation.

  • confdir may specify a configuration directory. The usual defaults apply.
  • extra_dbs is a list of additional indexes (Xapian directories).
  • writable decides if we can index new data through this connection.

A Db object is created by a connect() call and holds a connection to a Recoll index.

Db.close()
Closes the connection. You can’t do anything with the Db object after this.
Db.query(), Db.cursor()
These aliases return a blank Query object for this index.
Db.setAbstractParams(maxchars, contextwords)
Set the parameters used to build snippets (sets of keywords in context text fragments). maxchars defines the maximum total size of the abstract. contextwords defines how many terms are shown around the keyword.

Db.termMatch(match_type, expr, field=’‘, maxlen=-1, casesens=False, diacsens=False, lang=’english’)

Expand an expression against the index term list. Performs the basic function from the GUI term explorer tool. match_type can be either of wildcard, regexp or stem. Returns a list of terms expanded from the input expression.

A Query object (equivalent to a cursor in the Python DB API) is created by a Db.query() call. It is used to execute index searches.

Query.sortby(fieldname, ascending=True)
Sort results by fieldname, in ascending or descending order. Must be called before executing the search.

Query.execute(query_string, stemming=1, stemlang=”english”, fetchtext=False)

Starts a search for query_string, a RCL search language string. If the index stores the document texts and fetchtext is True, store the document extracted text in doc.text.
Query.executesd(SearchData, fetchtext=False)
Starts a search for the query defined by the SearchData object. If the index stores the document texts and fetchtext is True, store the document extracted text in doc.text.
Query.fetchmany(size=query.arraysize)
Fetches the next Doc objects in the current search results, and returns them as an array of the required size, which is by default the value of the arraysize data member.
Query.fetchone()
Fetches the next Doc object from the current search results. Generates a StopIteration exception if there are no results left.
Query.close()
Closes the query. The object is unusable after the call.
Query.scroll(value, mode=’relative’)
Adjusts the position in the current result set. mode can be relative or absolute.
Query.getgroups()
Retrieves the expanded query terms as a list of pairs. Meaningful only after executexx In each pair, the first entry is a list of user terms (of size one for simple terms, or more for group and phrase clauses), the second a list of query terms as derived from the user terms and used in the Xapian Query.
Query.getxquery()
Return the Xapian query description as a Unicode string. Meaningful only after executexx.
Query.highlight(text, ishtml = 0, methods = object)
Will insert <span “class=rclmatch”>, </span> tags around the match areas in the input text and return the modified text. ishtml can be set to indicate that the input text is HTML and that HTML special characters should not be escaped. methods if set should be an object with methods startMatch(i) and endMatch() which will be called for each match and should return a begin and end tag
Query.makedocabstract(doc, methods = object))
Create a snippets abstract for doc (a Doc object) by selecting text around the match terms. If methods is set, will also perform highlighting. See the highlight method.
Query.__iter__() and Query.next()
So that things like ``for doc in
query:`` will work.
Query.arraysize
Default number of records processed by fetchmany (r/w).
Query.rowcount
Number of records returned by the last execute.
Query.rownumber
Next index to be fetched from results. Normally increments after each fetchone() call, but can be set/reset before the call to effect seeking (equivalent to using scroll()). Starts at 0.

A Doc object contains index data for a given document. The data is extracted from the index when searching, or set by the indexer program when updating. The Doc object has many attributes to be read or set by its user. It mostly matches the Rcl::Doc C++ object. Some of the attributes are predefined, but, especially when indexing, others can be set, the name of which will be processed as field names by the indexing configuration. Inputs can be specified as Unicode or strings. Outputs are Unicode objects. All dates are specified as Unix timestamps, printed as strings. Please refer to the rcldb/rcldoc.cpp C++ file for a full description of the predefined attributes. Here follows a short list.

  • url the document URL but see also getbinurl()
  • ipath the document ipath for embedded documents.
  • fbytes, dbytes the document file and text sizes.
  • fmtime, dmtime the document file and document times.
  • xdocid the document Xapian document ID. This is useful if you want to access the document through a direct Xapian operation.
  • mtype the document MIME type.
  • Fields stored by default: author, filename, keywords, recipient

At query time, only the fields that are defined as stored either by default or in the fields configuration file will be meaningful in the Doc object. The document processed text may be present or not, depending if the index stores the text at all, and if it does, on the fetchtext query execute option. See also the rclextract module for accessing document contents.

get(key), [] operator

Retrieve the named document attribute. You can also use ``getattr(doc,

key)`` or doc.key.
doc.key = value

Set the the named document attribute. You can also use ``setattr(doc, key,

value)``.
getbinurl()
Retrieve the URL in byte array format (no transcoding), for use as parameter to a system call.
setbinurl(url)
Set the URL in byte array format (no transcoding).
items()
Return a dictionary of doc object keys/values
keys()
list of doc object keys (attribute names).

A SearchData object allows building a query by combining clauses, for execution by Query.executesd(). It can be used in replacement of the query language approach. The interface is going to change a little, so no detailed doc for now...

addclause(type=’and’|’or’|’excl’|’phrase’|’near’|’sub’, qstring=string, slack=0, field=’‘, stemming=1, subSearch=SearchData)

The rclextract module

Prior to RCL 1.25, index queries could not provide document content because it was never stored. RCL 1.25 and later usually store the document text, which can be optionally retrieved when running a query (see query.execute() above - the result is always plain text).

The rclextract module can give access to the original document and to the document text content (if not stored by the index, or to access an HTML version of the text). Acessing the original document is particularly useful if it is embedded (e.g. an email attachment).

You need to import the recoll module before the rclextract module.

Extractor(doc)
An Extractor object is built from a Doc object, output from a query.
Extractor.textextract(ipath)

Extract document defined by ipath and return a Doc object. The doc.text field has the document text converted to either text/plain or text/html according to doc.mimetype. The typical use would be as follows:

from recoll import recoll, rclextract

qdoc = query.fetchone()
extractor = recoll.Extractor(qdoc)
doc = extractor.textextract(qdoc.ipath)
# use doc.text, e.g. for previewing

Passing qdoc.ipath to textextract() is redundant, but reflects the fact that the Extractor object actually has the capability to access the other entries in a compound document.

Extractor.idoctofile(ipath, targetmtype, outfile=’‘)

Extracts document into an output file, which can be given explicitly or will be created as a temporary file to be deleted by the caller. Typical use:

from recoll import recoll, rclextract

qdoc = query.fetchone()
extractor = recoll.Extractor(qdoc)
filename = extractor.idoctofile(qdoc.ipath, qdoc.mimetype)

In all cases the output is a copy, even if the requested document is a regular system file, which may be wasteful in some cases. If you want to avoid this, you can test for a simple file document as follows:

not doc.ipath and (not "rclbes" in doc.keys() or doc["rclbes"] == "FS")
Search API usage example

The following sample would query the index with a user language string. See the python/samples directory inside the RCL source for other examples. The recollgui subdirectory has a very embryonic GUI which demonstrates the highlighting and data extraction functions.

#!/usr/bin/env python

from recoll import recoll

db = recoll.connect()
db.setAbstractParams(maxchars=80, contextwords=4)

query = db.query()
nres = query.execute("some user question")
print "Result count: ", nres
if nres > 5:
    nres = 5
for i in range(nres):
    doc = query.fetchone()
    print "Result #%d" % (query.rownumber,)
    for k in ("title", "size"):
        print k, ":", getattr(doc, k).encode('utf-8')
    abs = db.makeDocAbstract(doc, query).encode('utf-8')
    print abs
    print

Creating Python external indexers

The update API can be used to create an index from data which is not accessible to the regular RCL indexer, or structured to present difficulties to the RCL input handlers.

An indexer created using this API will be have equivalent work to do as the the Recoll file system indexer: look for modified documents, extract their text, call the API for indexing it, take care of purging the index out of data from documents which do not exist in the document store any more.

The data for such an external indexer should be stored in an index separate from any used by the RCL internal file system indexer. The reason is that the main document indexer purge pass (removal of deleted documents) would also remove all the documents belonging to the external indexer, as they were not seen during the filesystem walk. The main indexer documents would also probably be a problem for the external indexer own purge operation.

While there would be ways to enable multiple foreign indexers to cooperate on a single index, it is just simpler to use separate ones, and use the multiple index access capabilities of the query interface, if needed.

There are two parts in the update interface:

  • Methods inside the recoll module allow inserting data into the index, to make it accessible by the normal query interface.
  • An interface based on scripts execution is defined to allow either the GUI or the rclextract module to access original document data for previewing or editing.
Python update interface

The update methods are part of the recoll module described above. The connect() method is used with a writable=true parameter to obtain a writable Db object. The following Db object methods are then available.

addOrUpdate(udi, doc, parent_udi=None)

Add or update index data for a given document The ``

udi`` string must define a unique id for the

document. It is an opaque interface element and not interpreted inside Recoll. doc is a ``

Doc`` object, created from the data to be

indexed (the main text should be in doc.text). If ``

parent_udi`` is set, this is a unique

identifier for the top-level container (e.g. for the filesystem indexer, this would be the one which is an actual file).

delete(udi)
Purge index from all data for udi, and all documents (if any) which have a matrching parent_udi.
needUpdate(udi, sig)

Test if the index needs to be updated for the document identified by udi. If this call is to be used, the doc.sig field should contain a signature value when calling addOrUpdate(). The needUpdate() call then compares its parameter value with the stored sig for udi. sig is an opaque value, compared as a string.

The filesystem indexer uses a concatenation of the decimal string values for file size and update time, but a hash of the contents could also be used.

As a side effect, if the return value is false (the index is up to date), the call will set the existence flag for the document (and any subdocument defined by its parent_udi), so that a later purge() call will preserve them).

The use of needUpdate() and purge() is optional, and the indexer may use another method for checking the need to reindex or to delete stale entries.

purge()
Delete all documents that were not touched during the just finished indexing pass (since open-for-write). These are the documents for the needUpdate() call was not performed, indicating that they no longer exist in the primary storage system.
Query data access for external indexers (1.23)

RCL has internal methods to access document data for its internal (filesystem) indexer. An external indexer needs to provide data access methods if it needs integration with the GUI (e.g. preview function), or support for the rclextract module.

The index data and the access method are linked by the rclbes (recoll backend storage) Doc field. You should set this to a short string value identifying your indexer (e.g. the filesystem indexer uses either “FS” or an empty value, the Web history indexer uses “BGL”).

The link is actually performed inside a backends configuration file (stored in the configuration directory). This defines commands to execute to access data from the specified indexer. Example, for the mbox indexing sample found in the Recoll source (which sets rclbes="MBOX"):

[MBOX]
          fetch = /path/to/recoll/src/python/samples/rclmbox.py fetch
          makesig = path/to/recoll/src/python/samples/rclmbox.py makesig

fetch and makesig define two commands to execute to respectively retrieve the document text and compute the document signature (the example implementation uses the same script with different first parameters to perform both operations).

The scripts are called with three additional arguments: udi, url, ipath, stored with the document when it was indexed, and may use any or all to perform the requested operation. The caller expects the result data on stdout.

External indexer samples

The Recoll source tree has two samples of external indexers in the src/python/samples directory. The more interesting one is rclmbox.py which indexes a directory containing mbox folder files. It exercises most features in the update interface, and has a data access interface.

See the comments inside the file for more information.

Package compatibility with the previous version

The following code fragments can be used to ensure that code can run with both the old and the new API (as long as it does not use the new abilities of the new API of course).

Adapting to the new package structure:

try:
from recoll import recoll
from recoll import rclextract
hasextract = True
except:
import recoll
hasextract = False

Adapting to the change of nature of the next Query member. The same test can be used to choose to use the scroll() method (new) or set the next value (old).

rownum = query.next if type(query.next) == int else \
query.rownumber

Installation and configuration

Installing a binary copy

RCL binary copies are always distributed as regular packages for your system. They can be obtained either through the system’s normal software distribution framework (e.g. Debian/Ubuntu apt, FreeBSD ports, etc.), or from some type of “backports” repository providing versions newer than the standard ones, or found on the RCL WEB site in some cases. The most up-to-date information about Recoll packages can usually be found on the Recoll WEB site downloads page

There used to exist another form of binary install, as pre-compiled source trees, but these are just less convenient than the packages and don’t exist any more.

The package management tools will usually automatically deal with hard dependancies for packages obtained from a proper package repository. You will have to deal with them by hand for downloaded packages (for example, when dpkg complains about missing dependancies).

In all cases, you will have to check or install supporting applications for the file types that you want to index beyond those that are natively processed by RCL (text, HTML, email files, and a few others).

You should also maybe have a look at the configuration section (but this may not be necessary for a quick test with default parameters). Most parameters can be more conveniently set from the GUI interface.

Supporting packages

Note

The WIN installation of RCL is self-contained, and only needs Python 2.7 to be externally installed. WIN users can skip this section.

RCL uses external applications to index some file types. You need to install them for the file types that you wish to have indexed (these are run-time optional dependencies. None is needed for building or running RCL except for indexing their specific file type).

After an indexing pass, the commands that were found missing can be displayed from the recoll File menu. The list is stored in the missing text file inside the configuration directory.

A list of common file types which need external commands follows. Many of the handlers need the iconv command, which is not always listed as a dependancy.

Please note that, due to the relatively dynamic nature of this information, the most up to date version is now kept on RCLAPPS along with links to the home pages or best source/patches pages, and misc tips. The list below is not updated often and may be quite stale.

For many Linux distributions, most of the commands listed can be installed from the package repositories. However, the packages are sometimes outdated, or not the best version for RCL, so you should take a look at RCLAPPS if a file type is important to you.

As of RCL release 1.14, a number of XML-based formats that were handled by ad hoc handler code now use the xsltproc command, which usually comes with libxslt. These are: abiword, fb2 (ebooks), kword, openoffice, svg.

Now for the list:

  • Openoffice files need unzip and xsltproc.
  • PDF files need pdftotext which is part of Poppler (usually comes with the poppler-utils package). Avoid the original one from Xpdf.
  • Postscript files need pstotext. The original version has an issue with shell character in file names, which is corrected in recent packages. See RCLAPPS for more detail.
  • MS Word needs antiword. It is also useful to have wvWare installed as it may be be used as a fallback for some files which antiword does not handle.
  • MS Excel and PowerPoint are processed by internal Python handlers.
  • MS Open XML (docx) needs ``
    xsltproc``.
  • Wordperfect files need wpd2html from the libwpd (or libwpd-tools on Ubuntu) package.
  • RTF files need unrtf, which, in its older versions, has much trouble with non-western character sets. Many Linux distributions carry outdated unrtf versions. Check RCLAPPS for details.
  • TeX files need untex or detex. Check RCLAPPS for sources if it’s not packaged for your distribution.
  • dvi files need dvips.
  • djvu files need djvutxt and djvused from the DjVuLibre package.
  • Audio files: RCL releases 1.14 and later use a single Python handler based on mutagen for all audio file types.
  • Pictures: RCL uses the Exiftool Perl package to extract tag information. Most image file formats are supported. Note that there may not be much interest in indexing the technical tags (image size, aperture, etc.). This is only of interest if you store personal tags or textual descriptions inside the image files.
  • chm: files in Microsoft help format need Python and the pychm module (which needs chmlib).
  • ICS: up to RCL 1.13, iCalendar files need Python and the icalendar module. icalendar is not needed for newer versions, which use internal code.
  • Zip archives need Python (and the standard zipfile module).
  • Rar archives need Python, the rarfile Python module and the unrar utility.
  • Midi karaoke files need Python and the Midi module
  • Konqueror webarchive format with Python (uses the Tarfile module).
  • Mimehtml web archive format (support based on the email handler, which introduces some mild weirdness, but still usable).

Text, HTML, email folders, and Scribus files are processed internally. Lyx is used to index Lyx files. Many handlers need iconv and the standard sed and awk.

Building from source

Prerequisites

The following prerequisites are described in broad terms and not as specific package names (which will depend on the exact platform). The dependancies should be available as packages on most common Unix derivatives, and it should be quite uncommon that you would have to build one of them.

The shopping list:

  • The autoconf, automake and libtool triad. Only autoconf is needed for RCL 1.21 and earlier.

  • C++ compiler. Recent versions require C++11 compatibility (1.23 and later).

  • bison command (for RCL 1.21 and later).

  • xsltproc command. For building the documentation (for RCL 1.21 and later). This sometimes comes with the libxslt package. And also the Docbook XML and style sheet files.

  • Development files for Xapian core.

    Important

    If you are building Xapian for an older CPU (before Pentium 4 or Athlon 64), you need to add the --disable-sse flag to the configure command. Else all Xapian application will crash with an illegal instruction error.

  • Development files for Qt 4 or Qt 5. RCL 1.15.9 was the last version to support Qt 3. If you do not want to install or build the Qt Webkit module, RCL has a configuration option to disable its use (see further in the configuration section).

  • Development files for X11 and zlib.

  • Development files for Python (or use --disable-python-module).

  • You may also need libiconv. On Linux systems, the iconv interface is part of libc and you should not need to do anything special.

Check the RCL download page for up to date version information.

Building

RCL has been built on Linux, FreeBSD, Mac OS X, and Solaris, most versions after 2005 should be ok, maybe some older ones too (Solaris 8 is ok). If you build on another system, and need to modify things, I would very much welcome patches.

Configure options:.

  • --without-aspell will disable the code for phonetic matching of search terms.

  • --with-fam or --with-inotify will enable the code for real time indexing. Inotify support is enabled by default on recent Linux systems.

  • --with-qzeitgeist will enable sending Zeitgeist events about the visited search results, and needs the qzeitgeist package.

  • --disable-webkit is available from version 1.17 to implement the result list with a Qt QTextBrowser instead of a WebKit widget if you do not or can’t depend on the latter.

  • --disable-idxthreads is available from version 1.19 to suppress multithreading inside the indexing process. You can also use the run-time configuration to restrict recollindex to using a single thread, but the compile-time option may disable a few more unused locks. This only applies to the use of multithreading for the core index processing (data input). The RCL monitor mode always uses at least two threads of execution.

  • --disable-python-module will avoid building the Python module.

  • --disable-xattr will prevent fetching data from file extended attributes. Beyond a few standard attributes, fetching extended attributes data can only be useful is some application stores data in there, and also needs some simple configuration (see comments in the fields configuration file).

  • --enable-camelcase will enable splitting camelCase words. This is not enabled by default as it has the unfortunate side-effect of making some phrase searches quite confusing: ie, "MySQL manual" would be matched by "MySQL manual" and "my sql manual" but not ``“mysql

    manual”`` (only inside phrase searches).

  • --with-file-command Specify the version of the ‘file’ command to use (ie: –with-file-command=/usr/local/bin/file). Can be useful to enable the gnu version on systems where the native one is bad.

  • --disable-qtgui Disable the Qt interface. Will allow building the indexer and the command line search program in absence of a Qt environment.

  • --disable-x11mon Disable X11 connection monitoring inside recollindex. Together with –disable-qtgui, this allows building recoll without Qt and X11.

  • --disable-userdoc will avoid building the user manual. This avoids having to install the Docbook XML/XSL files and the TeX toolchain used for translating the manual to PDF.

  • --disable-pic (RCL versions up to 1.21 only) will compile RCL with position-dependant code. This is incompatible with building the KIO or the Python or PHP extensions, but might yield very marginally faster code.

  • Of course the usual autoconf configure options, like --prefix apply.

Normal procedure (for source extracted from a tar distribution):

cd recoll-xxx
./configure
make
(practices usual hardship-repelling invocations)

When building from source cloned from the git repository, you also need to install autoconf, automake, and libtool and you must execute ``sh

autogen.sh`` in the top source directory before running

configure.

Installing

Use make install in the root of the source tree. This will copy the commands to prefix/bin and the sample configuration files, scripts and other shared data to prefix/share/recoll.

Python API package

The Python interface can be found in the source tree, under the python/recoll directory.

As of RCL 1.19, the module can be compiled for Python3.

The normal RCL build procedure (see above) installs the API package for the default system version (python) along with the main code. The package for other Python versions (e.g. python3 if the system default is python2) must be explicitely built and installed.

The python/recoll/ directory contains the usual setup.py. After configuring and building the main RCL code, you can use the script to build and install the Python module:

cd recoll-xxx/python/recoll
pythonX setup.py build
sudo pythonX setup.py install

Building on Solaris

We did not test building the GUI on Solaris for recent versions. You will need at least Qt 4.4. There are some hints on an old web site page, they may still be valid.

Someone did test the 1.19 indexer and Python module build, they do work, with a few minor glitches. Be sure to use GNU make and install.

Configuration overview

Most of the parameters specific to the recoll GUI are set through the Preferences menu and stored in the standard Qt place ($HOME/.config/Recoll.org/recoll.conf). You probably do not want to edit this by hand.

RCL indexing options are set inside text configuration files located in a configuration directory. There can be several such directories, each of which defines the parameters for one index.

The configuration files can be edited by hand or through the Index configuration dialog (Preferences menu). The GUI tool will try to respect your formatting and comments as much as possible, so it is quite possible to use both approaches on the same configuration.

The most accurate documentation for the configuration parameters is given by comments inside the default files, and we will just give a general overview here.

For each index, there are at least two sets of configuration files. System-wide configuration files are kept in a directory named like /usr/share/recoll/examples, and define default values, shared by all indexes. For each index, a parallel set of files defines the customized parameters.

The default location of the customized configuration is the .recoll directory in your home. Most people will only use this directory.

This location can be changed, or others can be added with the RECOLL_CONFDIR environment variable or the -c option parameter to recoll and recollindex.

In addition (as of RCL version 1.19.7), it is possible to specify two additional configuration directories which will be stacked before and after the user configuration directory. These are defined by the RECOLL_CONFTOP and RECOLL_CONFMID environment variables. Values from configuration files inside the top directory will override user ones, values from configuration files inside the middle directory will override system ones and be overriden by user ones. These two variables may be of use to applications which augment RCL functionality, and need to add configuration data without disturbing the user’s files. Please note that the two, currently single, values will probably be interpreted as colon-separated lists in the future: do not use colon characters inside the directory paths.

If the .recoll directory does not exist when recoll or recollindex are started, it will be created with a set of empty configuration files. recoll will give you a chance to edit the configuration file before starting indexing. recollindex will proceed immediately. To avoid mistakes, the automatic directory creation will only occur for the default location, not if -c or RECOLL_CONFDIR were used (in the latter cases, you will have to create the directory).

All configuration files share the same format. For example, a short extract of the main configuration file might look as follows:

# Space-separated list of files and directories to index.
topdirs =  ~/docs /usr/share/doc

[~/somedirectory-with-utf8-txt-files]
defaultcharset = utf-8

There are three kinds of lines:

  • Comment (starts with #) or empty.
  • Parameter affectation (name = value).
  • Section definition ([somedirname]).

Long lines can be broken by ending each incomplete part with a backslash (\).

Depending on the type of configuration file, section definitions either separate groups of parameters or allow redefining some parameters for a directory sub-tree. They stay in effect until another section definition, or the end of file, is encountered. Some of the parameters used for indexing are looked up hierarchically from the current directory location upwards. Not all parameters can be meaningfully redefined, this is specified for each in the next section.

Important

Global parameters must not be defined in a directory subsection, else they will not be found at all by the RCL code, which looks for them at the top level (e.g. skippedPaths).

When found at the beginning of a file path, the tilde character (~) is expanded to the name of the user’s home directory, as a shell would do.

Some parameters are lists of strings. White space is used for separation. List elements with embedded spaces can be quoted using double-quotes. Double quotes inside these elements can be escaped with a backslash.

No value inside a configuration file can contain a newline character. Long lines can be continued by escaping the physical newline with backslash, even inside quoted strings.

astringlist =  "some string \
with spaces"
thesame = "some string with spaces"

Parameters which are not part of string lists can’t be quoted, and leading and trailing space characters are stripped before the value is used.

Encoding issues.

Most of the configuration parameters are plain ASCII. Two particular sets of values may cause encoding issues:

  • File path parameters may contain non-ascii characters and should use the exact same byte values as found in the file system directory. Usually, this means that the configuration file should use the system default locale encoding.
  • The unac_except_trans parameter should be encoded in UTF-8. If your system locale is not UTF-8, and you need to also specify non-ascii file paths, this poses a difficulty because common text editors cannot handle multiple encodings in a single file. In this relatively unlikely case, you can edit the configuration file as two separate text files with appropriate encodings, and concatenate them to create the complete configuration.

Environment variables

RECOLL_CONFDIR
Defines the main configuration directory.
RECOLL_TMPDIR, TMPDIR
Locations for temporary files, in this order of priority. The default if none of these is set is to use /tmp. Big temporary files may be created during indexing, mostly for decompressing, and also for processing, e.g. email attachments.
RECOLL_CONFTOP, RECOLL_CONFMID
Allow adding configuration directories with priorities below and above the user directory (see above the Configuration overview section for details).
RECOLL_EXTRA_DBS, RECOLL_ACTIVE_EXTRA_DBS
Help for setting up external indexes. See this paragraph for explanations.
RECOLL_DATADIR
Defines replacement for the default location of Recoll data files, normally found in, e.g., /usr/share/recoll).
RECOLL_FILTERSDIR
Defines replacement for the default location of Recoll filters, normally found in, e.g., /usr/share/recoll/filters).
ASPELL_PROG
aspell program to use for creating the spelling dictionary. The result has to be compatible with the libaspell which RCL is using.
VARNAME
Blabla

Recoll main configuration file, recoll.conf

Parameters affecting what documents we index
topdirs
Space-separated list of files or directories to recursively index. Default to ~ (indexes $HOME). You can use symbolic links in the list, they will be followed, independantly of the value of the followLinks variable.
monitordirs
Space-separated list of files or directories to monitor for updates. When running the real-time indexer, this allows monitoring only a subset of the whole indexed area. The elements must be included in the tree defined by the ‘topdirs’ members.
skippedNames
Files and directories which should be ignored. White space separated list of wildcard patterns (simple ones, not paths, must contain no / ), which will be tested against file and directory names. The list in the default configuration does not exclude hidden directories (names beginning with a dot), which means that it may index quite a few things that you do not want. On the other hand, email user agents like Thunderbird usually store messages in hidden directories, and you probably want this indexed. One possible solution is to have ”.*” in “skippedNames”, and add things like “~/.thunderbird” “~/.evolution” to “topdirs”. Not even the file names are indexed for patterns in this list, see the “noContentSuffixes” variable for an alternative approach which indexes the file names. Can be redefined for any subtree.
skippedNames-
List of name endings to remove from the default skippedNames list.
skippedNames+
List of name endings to add to the default skippedNames list.
noContentSuffixes
List of name endings (not necessarily dot-separated suffixes) for which we don’t try MIME type identification, and don’t uncompress or index content. Only the names will be indexed. This complements the now obsoleted recoll_noindex list from the mimemap file, which will go away in a future release (the move from mimemap to recoll.conf allows editing the list through the GUI). This is different from skippedNames because these are name ending matches only (not wildcard patterns), and the file name itself gets indexed normally. This can be redefined for subdirectories.
noContentSuffixes-
List of name endings to remove from the default noContentSuffixes list.
noContentSuffixes+
List of name endings to add to the default noContentSuffixes list.
skippedPaths
Absolute paths we should not go into. Space-separated list of wildcard expressions for absolute filesystem paths. Must be defined at the top level of the configuration file, not in a subsection. Can contain files and directories. The database and configuration directories will automatically be added. The expressions are matched using ‘fnmatch(3)’ with the FNM_PATHNAME flag set by default. This means that ‘/’ characters must be matched explicitely. You can set ‘skippedPathsFnmPathname’ to 0 to disable the use of FNM_PATHNAME (meaning that ‘/*/dir3’ will match ‘/dir1/dir2/dir3’). The default value contains the usual mount point for removable media to remind you that it is a bad idea to have Recoll work on these (esp. with the monitor: media gets indexed on mount, all data gets erased on unmount). Explicitely adding ‘/media/xxx’ to the ‘topdirs’ variable will override this.
skippedPathsFnmPathname
Set to 0 to override use of FNM_PATHNAME for matching skipped paths.
nowalkfn
File name which will cause its parent directory to be skipped. Any directory containing a file with this name will be skipped as if it was part of the skippedPaths list. Ex: .recoll-noindex
daemSkippedPaths
skippedPaths equivalent specific to real time indexing. This enables having parts of the tree which are initially indexed but not monitored. If daemSkippedPaths is not set, the daemon uses skippedPaths.
zipUseSkippedNames
Use skippedNames inside Zip archives. Fetched directly by the rclzip handler. Skip the patterns defined by skippedNames inside Zip archives. Can be redefined for subdirectories. See https://www.lesbonscomptes.com/recoll/faqsandhowtos/FilteringOutZipArchiveMembers.html
zipSkippedNames
Space-separated list of wildcard expressions for names that should be ignored inside zip archives. This is used directly by the zip handler. If zipUseSkippedNames is not set, zipSkippedNames defines the patterns to be skipped inside archives. If zipUseSkippedNames is set, the two lists are concatenated and used. Can be redefined for subdirectories. See https://www.lesbonscomptes.com/recoll/faqsandhowtos/FilteringOutZipArchiveMembers.html
followLinks
Follow symbolic links during indexing. The default is to ignore symbolic links to avoid multiple indexing of linked files. No effort is made to avoid duplication when this option is set to true. This option can be set individually for each of the ‘topdirs’ members by using sections. It can not be changed below the ‘topdirs’ level. Links in the ‘topdirs’ list itself are always followed.
indexedmimetypes
Restrictive list of indexed mime types. Normally not set (in which case all supported types are indexed). If it is set, only the types from the list will have their contents indexed. The names will be indexed anyway if indexallfilenames is set (default). MIME type names should be taken from the mimemap file (the values may be different from xdg-mime or file -i output in some cases). Can be redefined for subtrees.
excludedmimetypes
List of excluded MIME types. Lets you exclude some types from indexing. MIME type names should be taken from the mimemap file (the values may be different from xdg-mime or file -i output in some cases) Can be redefined for subtrees.
nomd5types
Don’t compute md5 for these types. md5 checksums are used only for deduplicating results, and can be very expensive to compute on multimedia or other big files. This list lets you turn off md5 computation for selected types. It is global (no redefinition for subtrees). At the moment, it only has an effect for external handlers (exec and execm). The file types can be specified by listing either MIME types (e.g. audio/mpeg) or handler names (e.g. rclaudio).
compressedfilemaxkbs
Size limit for compressed files. We need to decompress these in a temporary directory for identification, which can be wasteful in some cases. Limit the waste. Negative means no limit. 0 results in no processing of any compressed file. Default 50 MB.
textfilemaxmbs
Size limit for text files. Mostly for skipping monster logs. Default 20 MB.
indexallfilenames
Index the file names of unprocessed files Index the names of files the contents of which we don’t index because of an excluded or unsupported MIME type.
usesystemfilecommand
Use a system command for file MIME type guessing as a final step in file type identification This is generally useful, but will usually cause the indexing of many bogus ‘text’ files. See ‘systemfilecommand’ for the command used.
systemfilecommand
Command used to guess MIME types if the internal methods fails This should be a “file -i” workalike. The file path will be added as a last parameter to the command line. ‘xdg-mime’ works better than the traditional ‘file’ command, and is now the configured default (with a hard-coded fallback to ‘file’)
processwebqueue
Decide if we process the Web queue. The queue is a directory where the Recoll Web browser plugins create the copies of visited pages.
textfilepagekbs
Page size for text files. If this is set, text/plain files will be divided into documents of approximately this size. Will reduce memory usage at index time and help with loading data in the preview window at query time. Particularly useful with very big files, such as application or system logs. Also see textfilemaxmbs and compressedfilemaxkbs.
membermaxkbs
Size limit for archive members. This is passed to the filters in the environment as RECOLL_FILTER_MAXMEMBERKB.
Parameters affecting how we generate terms and organize the index
indexStripChars
Decide if we store character case and diacritics in the index. If we do, searches sensitive to case and diacritics can be performed, but the index will be bigger, and some marginal weirdness may sometimes occur. The default is a stripped index. When using multiple indexes for a search, this parameter must be defined identically for all. Changing the value implies an index reset.
indexStoreDocText
Decide if we store the documents’ text content in the index. Storing the text allows extracting snippets from it at query time, instead of building them from index position data. Newer Xapian index formats have rendered our use of positions list unacceptably slow in some cases. The last Xapian index format with good performance for the old method is Chert, which is default for 1.2, still supported but not default in 1.4 and will be dropped in 1.6. The stored document text is translated from its original format to UTF-8 plain text, but not stripped of upper-case, diacritics, or punctuation signs. Storing it increases the index size by 10-20% typically, but also allows for nicer snippets, so it may be worth enabling it even if not strictly needed for performance if you can afford the space. The variable only has an effect when creating an index, meaning that the xapiandb directory must not exist yet. Its exact effect depends on the Xapian version. For Xapian 1.4, if the variable is set to 0, the Chert format will be used, and the text will not be stored. If the variable is 1, Glass will be used, and the text stored. For Xapian 1.2, and for versions after 1.5 and newer, the index format is always the default, but the variable controls if the text is stored or not, and the abstract generation method. With Xapian 1.5 and later, and the variable set to 0, abstract generation may be very slow, but this setting may still be useful to save space if you do not use abstract generation at all.
nonumbers
Decides if terms will be generated for numbers. For example “123”, “1.5e6”, 192.168.1.4, would not be indexed if nonumbers is set (“value123” would still be). Numbers are often quite interesting to search for, and this should probably not be set except for special situations, ie, scientific documents with huge amounts of numbers in them, where setting nonumbers will reduce the index size. This can only be set for a whole index, not for a subtree.
dehyphenate
Determines if we index ‘coworker’ also when the input is ‘co-worker’. This is new in version 1.22, and on by default. Setting the variable to off allows restoring the previous behaviour.
backslashasletter
Process backslash as normal letter This may make sense for people wanting to index TeX commands as such but is not of much general use.
maxtermlength
Maximum term length. Words longer than this will be discarded. The default is 40 and used to be hard-coded, but it can now be adjusted. You need an index reset if you change the value.
nocjk
Decides if specific East Asian (Chinese Korean Japanese) characters/word splitting is turned off. This will save a small amount of CPU if you have no CJK documents. If your document base does include such text but you are not interested in searching it, setting nocjk may be a significant time and space saver.
cjkngramlen
This lets you adjust the size of n-grams used for indexing CJK text. The default value of 2 is probably appropriate in most cases. A value of 3 would allow more precision and efficiency on longer words, but the index will be approximately twice as large.
indexstemminglanguages
Languages for which to create stemming expansion data. Stemmer names can be found by executing ‘recollindex -l’, or this can also be set from a list in the GUI.
defaultcharset
Default character set. This is used for files which do not contain a character set definition (e.g.: text/plain). Values found inside files, e.g. a ‘charset’ tag in HTML documents, will override it. If this is not set, the default character set is the one defined by the NLS environment ($LC_ALL, $LC_CTYPE, $LANG), or ultimately iso-8859-1 (cp-1252 in fact). If for some reason you want a general default which does not match your LANG and is not 8859-1, use this variable. This can be redefined for any sub-directory.
unac_except_trans
A list of characters, encoded in UTF-8, which should be handled specially when converting text to unaccented lowercase. For example, in Swedish, the letter a with diaeresis has full alphabet citizenship and should not be turned into an a. Each element in the space-separated list has the special character as first element and the translation following. The handling of both the lowercase and upper-case versions of a character should be specified, as appartenance to the list will turn-off both standard accent and case processing. The value is global and affects both indexing and querying. Examples: Swedish: unac_except_trans = ää Ää öö Öö üü Üü ßss œoe Œoe æae Æae ffff fifi flfl åå Åå . German: unac_except_trans = ää Ää öö Öö üü Üü ßss œoe Œoe æae Æae ffff fifi flfl In French, you probably want to decompose oe and ae and nobody would type a German ß unac_except_trans = ßss œoe Œoe æae Æae ffff fifi flfl . The default for all until someone protests follows. These decompositions are not performed by unac, but it is unlikely that someone would type the composed forms in a search. unac_except_trans = ßss œoe Œoe æae Æae ffff fifi flfl
maildefcharset
Overrides the default character set for email messages which don’t specify one. This is mainly useful for readpst (libpst) dumps, which are utf-8 but do not say so.
localfields
Set fields on all files (usually of a specific fs area). Syntax is the usual: name = value ; attr1 = val1 ; [...] value is empty so this needs an initial semi-colon. This is useful, e.g., for setting the rclaptg field for application selection inside mimeview.
testmodifusemtime
Use mtime instead of ctime to test if a file has been modified. The time is used in addition to the size, which is always used. Setting this can reduce re-indexing on systems where extended attributes are used (by some other application), but not indexed, because changing extended attributes only affects ctime. Notes: - This may prevent detection of change in some marginal file rename cases (the target would need to have the same size and mtime). - You should probably also set noxattrfields to 1 in this case, except if you still prefer to perform xattr indexing, for example if the local file update pattern makes it of value (as in general, there is a risk for pure extended attributes updates without file modification to go undetected). Perform a full index reset after changing this.
noxattrfields
Disable extended attributes conversion to metadata fields. This probably needs to be set if testmodifusemtime is set.
metadatacmds
Define commands to gather external metadata, e.g. tmsu tags. There can be several entries, separated by semi-colons, each defining which field name the data goes into and the command to use. Don’t forget the initial semi-colon. All the field names must be different. You can use aliases in the “field” file if necessary. As a not too pretty hack conceded to convenience, any field name beginning with “rclmulti” will be taken as an indication that the command returns multiple field values inside a text blob formatted as a recoll configuration file (“fieldname = fieldvalue” lines). The rclmultixx name will be ignored, and field names and values will be parsed from the data. Example: metadatacmds = ; tags = tmsu tags %f; rclmulti1 = cmdOutputsConf %f
Parameters affecting where and how we store things
cachedir
Top directory for Recoll data. Recoll data directories are normally located relative to the configuration directory (e.g. ~/.recoll/xapiandb, ~/.recoll/mboxcache). If ‘cachedir’ is set, the directories are stored under the specified value instead (e.g. if cachedir is ~/.cache/recoll, the default dbdir would be ~/.cache/recoll/xapiandb). This affects dbdir, webcachedir, mboxcachedir, aspellDicDir, which can still be individually specified to override cachedir. Note that if you have multiple configurations, each must have a different cachedir, there is no automatic computation of a subpath under cachedir.
maxfsoccuppc
Maximum file system occupation over which we stop indexing. The value is a percentage, corresponding to what the “Capacity” df output column shows. The default value is 0, meaning no checking.
dbdir
Xapian database directory location. This will be created on first indexing. If the value is not an absolute path, it will be interpreted as relative to cachedir if set, or the configuration directory (-c argument or $RECOLL_CONFDIR). If nothing is specified, the default is then ~/.recoll/xapiandb/
idxstatusfile
Name of the scratch file where the indexer process updates its status. Default: idxstatus.txt inside the configuration directory.
mboxcachedir
Directory location for storing mbox message offsets cache files. This is normally ‘mboxcache’ under cachedir if set, or else under the configuration directory, but it may be useful to share a directory between different configurations.
mboxcacheminmbs
Minimum mbox file size over which we cache the offsets. There is really no sense in caching offsets for small files. The default is 5 MB.
webcachedir
Directory where we store the archived web pages. This is only used by the web history indexing code Default: cachedir/webcache if cachedir is set, else $RECOLL_CONFDIR/webcache
webcachemaxmbs
Maximum size in MB of the Web archive. This is only used by the web history indexing code. Default: 40 MB. Reducing the size will not physically truncate the file.
webqueuedir
The path to the Web indexing queue. This used to be hard-coded in the old plugin as ~/.recollweb/ToIndex so there would be no need or possibility to change it, but the WebExtensions plugin now downloads the files to the user Downloads directory, and a script moves them to webqueuedir. The script reads this value from the config so it has become possible to change it.
webdownloadsdir
The path to browser downloads directory. This is where the new browser add-on extension has to create the files. They are then moved by a script to webqueuedir.
aspellDicDir
Aspell dictionary storage directory location. The aspell dictionary (aspdict.(lang).rws) is normally stored in the directory specified by cachedir if set, or under the configuration directory.
filtersdir
Directory location for executable input handlers. If RECOLL_FILTERSDIR is set in the environment, we use it instead. Defaults to $prefix/share/recoll/filters. Can be redefined for subdirectories.
iconsdir
Directory location for icons. The only reason to change this would be if you want to change the icons displayed in the result list. Defaults to $prefix/share/recoll/images
Parameters affecting indexing performance and resource usage
idxflushmb
Threshold (megabytes of new data) where we flush from memory to disk index. Setting this allows some control over memory usage by the indexer process. A value of 0 means no explicit flushing, which lets Xapian perform its own thing, meaning flushing every $XAPIAN_FLUSH_THRESHOLD documents created, modified or deleted: as memory usage depends on average document size, not only document count, the Xapian approach is is not very useful, and you should let Recoll manage the flushes. The program compiled value is 0. The configured default value (from this file) is now 50 MB, and should be ok in many cases. You can set it as low as 10 to conserve memory, but if you are looking for maximum speed, you may want to experiment with values between 20 and 200. In my experience, values beyond this are always counterproductive. If you find otherwise, please drop me a note.
filtermaxseconds
Maximum external filter execution time in seconds. Default 1200 (20mn). Set to 0 for no limit. This is mainly to avoid infinite loops in postscript files (loop.ps)
filtermaxmbytes
Maximum virtual memory space for filter processes (setrlimit(RLIMIT_AS)), in megabytes. Note that this includes any mapped libs (there is no reliable Linux way to limit the data space only), so we need to be a bit generous here. Anything over 2000 will be ignored on 32 bits machines.
thrQSizes
Stage input queues configuration. There are three internal queues in the indexing pipeline stages (file data extraction, terms generation, index update). This parameter defines the queue depths for each stage (three integer values). If a value of -1 is given for a given stage, no queue is used, and the thread will go on performing the next stage. In practise, deep queues have not been shown to increase performance. Default: a value of 0 for the first queue tells Recoll to perform autoconfiguration based on the detected number of CPUs (no need for the two other values in this case). Use thrQSizes = -1 -1 -1 to disable multithreading entirely.
thrTCounts
Number of threads used for each indexing stage. The three stages are: file data extraction, terms generation, index update). The use of the counts is also controlled by some special values in thrQSizes: if the first queue depth is 0, all counts are ignored (autoconfigured); if a value of -1 is used for a queue depth, the corresponding thread count is ignored. It makes no sense to use a value other than 1 for the last stage because updating the Xapian index is necessarily single-threaded (and protected by a mutex).
Miscellaneous parameters
loglevel
Log file verbosity 1-6. A value of 2 will print only errors and warnings. 3 will print information like document updates, 4 is quite verbose and 6 very verbose.
logfilename
Log file destination. Use ‘stderr’ (default) to write to the console.
idxloglevel
Override loglevel for the indexer.
idxlogfilename
Override logfilename for the indexer.
daemloglevel
Override loglevel for the indexer in real time mode. The default is to use the idx... values if set, else the log... values.
daemlogfilename
Override logfilename for the indexer in real time mode. The default is to use the idx... values if set, else the log... values.
orgidxconfdir
Original location of the configuration directory. This is used exclusively for movable datasets. Locating the configuration directory inside the directory tree makes it possible to provide automatic query time path translations once the data set has moved (for example, because it has been mounted on another location).
curidxconfdir
Current location of the configuration directory. Complement orgidxconfdir for movable datasets. This should be used if the configuration directory has been copied from the dataset to another location, either because the dataset is readonly and an r/w copy is desired, or for performance reasons. This records the original moved location before copy, to allow path translation computations. For example if a dataset originally indexed as ‘/home/me/mydata/config’ has been mounted to ‘/media/me/mydata’, and the GUI is running from a copied configuration, orgidxconfdir would be ‘/home/me/mydata/config’, and curidxconfdir (as set in the copied configuration) would be ‘/media/me/mydata/config’.
idxrundir
Indexing process current directory. The input handlers sometimes leave temporary files in the current directory, so it makes sense to have recollindex chdir to some temporary directory. If the value is empty, the current directory is not changed. If the value is (literal) tmp, we use the temporary directory as set by the environment (RECOLL_TMPDIR else TMPDIR else /tmp). If the value is an absolute path to a directory, we go there.
checkneedretryindexscript
Script used to heuristically check if we need to retry indexing files which previously failed. The default script checks the modified dates on /usr/bin and /usr/local/bin. A relative path will be looked up in the filters dirs, then in the path. Use an absolute path to do otherwise.
recollhelperpath
Additional places to search for helper executables. This is only used on Windows for now.
idxabsmlen
Length of abstracts we store while indexing. Recoll stores an abstract for each indexed file. The text can come from an actual ‘abstract’ section in the document or will just be the beginning of the document. It is stored in the index so that it can be displayed inside the result lists without decoding the original file. The idxabsmlen parameter defines the size of the stored abstract. The default value is 250 bytes. The search interface gives you the choice to display this stored text or a synthetic abstract built by extracting text around the search terms. If you always prefer the synthetic abstract, you can reduce this value and save a little space.
idxmetastoredlen
Truncation length of stored metadata fields. This does not affect indexing (the whole field is processed anyway), just the amount of data stored in the index for the purpose of displaying fields inside result lists or previews. The default value is 150 bytes which may be too low if you have custom fields.
idxtexttruncatelen
Truncation length for all document texts. Only index the beginning of documents. This is not recommended except if you are sure that the interesting keywords are at the top and have severe disk space issues.
aspellLanguage
Language definitions to use when creating the aspell dictionary. The value must match a set of aspell language definition files. You can type “aspell dicts” to see a list The default if this is not set is to use the NLS environment to guess the value.
aspellAddCreateParam
Additional option and parameter to aspell dictionary creation command. Some aspell packages may need an additional option (e.g. on Debian Jessie: –local-data-dir=/usr/lib/aspell). See Debian bug 772415.
aspellKeepStderr
Set this to have a look at aspell dictionary creation errors. There are always many, so this is mostly for debugging.
noaspell
Disable aspell use. The aspell dictionary generation takes time, and some combinations of aspell version, language, and local terms, result in aspell crashing, so it sometimes makes sense to just disable the thing.
monauxinterval
Auxiliary database update interval. The real time indexer only updates the auxiliary databases (stemdb, aspell) periodically, because it would be too costly to do it for every document change. The default period is one hour.
monixinterval
Minimum interval (seconds) between processings of the indexing queue. The real time indexer does not process each event when it comes in, but lets the queue accumulate, to diminish overhead and to aggregate multiple events affecting the same file. Default 30 S.
mondelaypatterns
Timing parameters for the real time indexing. Definitions for files which get a longer delay before reindexing is allowed. This is for fast-changing files, that should only be reindexed once in a while. A list of wildcardPattern:seconds pairs. The patterns are matched with fnmatch(pattern, path, 0) You can quote entries containing white space with double quotes (quote the whole entry, not the pattern). The default is empty. Example: mondelaypatterns = *.log:20 “*with spaces.*:30”
monioniceclass
ionice class for the real time indexing process On platforms where this is supported. The default value is 3.
monioniceclassdata
ionice class parameter for the real time indexing process. On platforms where this is supported. The default is empty.
Query-time parameters (no impact on the index)
autodiacsens
auto-trigger diacritics sensitivity (raw index only). IF the index is not stripped, decide if we automatically trigger diacritics sensitivity if the search term has accented characters (not in unac_except_trans). Else you need to use the query language and the “D” modifier to specify diacritics sensitivity. Default is no.
autocasesens
auto-trigger case sensitivity (raw index only). IF the index is not stripped (see indexStripChars), decide if we automatically trigger character case sensitivity if the search term has upper-case characters in any but the first position. Else you need to use the query language and the “C” modifier to specify character-case sensitivity. Default is yes.
maxTermExpand
Maximum query expansion count for a single term (e.g.: when using wildcards). This only affects queries, not indexing. We used to not limit this at all (except for filenames where the limit was too low at 1000), but it is unreasonable with a big index. Default 10000.
maxXapianClauses
Maximum number of clauses we add to a single Xapian query. This only affects queries, not indexing. In some cases, the result of term expansion can be multiplicative, and we want to avoid eating all the memory. Default 50000.
snippetMaxPosWalk
Maximum number of positions we walk while populating a snippet for the result list. The default of 1,000,000 may be insufficient for very big documents, the consequence would be snippets with possibly meaning-altering missing words.
Parameters for the PDF input script
pdfocr
Attempt OCR of PDF files with no text content if both tesseract and pdftoppm are installed. The default is off because OCR is so very slow.
pdfocrlang
Language to assume for PDF OCR. This is very important for having a reasonable rate of errors with tesseract. This can also be set through a configuration variable or directory-local parameters. See the rclpdf.py script.
pdfattach
Enable PDF attachment extraction by executing pdftk (if available). This is normally disabled, because it does slow down PDF indexing a bit even if not one attachment is ever found.
pdfextrameta
Extract text from selected XMP metadata tags. This is a space-separated list of qualified XMP tag names. Each element can also include a translation to a Recoll field name, separated by a ‘|’ character. If the second element is absent, the tag name is used as the Recoll field names. You will also need to add specifications to the ‘fields’ file to direct processing of the extracted data.
pdfextrametafix
Define name of XMP field editing script. This defines the name of a script to be loaded for editing XMP field values. The script should define a ‘MetaFixer’ class with a metafix() method which will be called with the qualified tag name and value of each selected field, for editing or erasing. A new instance is created for each document, so that the object can keep state for, e.g. eliminating duplicate values.
Parameters set for specific locations
mhmboxquirks
Enable thunderbird/mozilla-seamonkey mbox format quirks Set this for the directory where the email mbox files are stored.

The fields file

This file contains information about dynamic fields handling in RCL. Some very basic fields have hard-wired behaviour, and, mostly, you should not change the original data inside the fields file. But you can create custom fields fitting your data and handle them just like they were native ones.

The fields file has several sections, which each define an aspect of fields processing. Quite often, you’ll have to modify several sections to obtain the desired behaviour.

We will only give a short description here, you should refer to the comments inside the default file for more detailed information.

Field names should be lowercase alphabetic ASCII.

[prefixes]
A field becomes indexed (searchable) by having a prefix defined in this section. There is a more complete explanation of what prefixes are in used by a standard recoll installation. In a nutshell: extension prefixes should be all caps, begin with XY, and short. E.g. XYMFLD.
[values]
Fields listed in this section will be stored as XAP values inside the index. This makes them available for range queries, allowing to filter results according to the field value. This feature currently supports string and integer data. See the comments in the file for more detail
[stored]
A field becomes stored (displayable inside results) by having its name listed in this section (typically with an empty value).
[aliases]
This section defines lists of synonyms for the canonical names used inside the [prefixes] and [stored] sections
[queryaliases]
This section also defines aliases for the canonic field names, with the difference that the substitution will only be used at query time, avoiding any possibility that the value would pick-up random metadata from documents.
handler-specific sections
Some input handlers may need specific configuration for handling fields. Only the email message handler currently has such a section (named [mail]). It allows indexing arbitrary email headers in addition to the ones indexed by default. Other such sections may appear in the future.

Here follows a small example of a personal fields file. This would extract a specific email header and use it as a searchable field, with data displayable inside result lists. (Side note: as the email handler does no decoding on the values, only plain ascii headers can be indexed, and only the first occurrence will be used for headers that occur several times).

[prefixes]
        # Index mailmytag contents (with the given prefix)
        mailmytag = XMTAG

        [stored]
        # Store mailmytag inside the document data record (so that it can be
        # displayed - as %(mailmytag) - in result lists).
        mailmytag =

        [queryaliases]
        filename = fn
        containerfilename = cfn

        [mail]
        # Extract the X-My-Tag mail header, and use it internally with the
        # mailmytag field name
        x-my-tag = mailmytag
Extended attributes in the fields file

RCL versions 1.19 and later process user extended file attributes as documents fields by default.

Attributes are processed as fields of the same name, after removing the user prefix on Linux.

The [xattrtofields] section of the fields file allows specifying translations from extended attributes names to RCL field names. An empty translation disables use of the corresponding attribute data.

The mimemap file

mimemap specifies the file name extension to MIME type mappings.

For file names without an extension, or with an unknown one, a system command (file -i, or xdg-mime) will be executed to determine the MIME type (this can be switched off, or the command changed inside the main configuration file).

All extension values in mimemap must be entered in lower case. File names extensions are lower-cased for comparison during indexing, meaning that an upper case mimemap entry will never be matched.

The mappings can be specified on a per-subtree basis, which may be useful in some cases. Example: okular notes have a .xml extension but should be handled specially, which is possible because they are usually all located in one place. Example:

[~/.kde/share/apps/okular/docdata]
        .xml = application/x-okular-notes

The recoll_noindex mimemap variable has been moved to recoll.conf and renamed to noContentSuffixes, while keeping the same function, as of RCL version 1.21. For older RCL versions, see the documentation for noContentSuffixes but use recoll_noindex in mimemap.

The mimeconf file

The main purpose of the mimeconf file is to specify how the different MIME types are handled for indexing. This is done in the [index] section, which should not be modified casually. See the comments in the file.

The file also contains other definitions which affect the query language and the GUI, and which, in retrospect, should have been stored elsewhere.

The [icons] section allows you to change the icons which are displayed by the recoll GUI in the result lists (the values are the basenames of the png images inside the iconsdir directory (which is itself defined in recoll.conf).

The [categories] section defines the groupings of MIME types into categories as used when adding an rclcat clause to a query language query. rclcat clauses are also used by the default guifilters buttons in the GUI (see next).

The filter controls appear at the top of the recoll GUI, either as checkboxes just above the result list, or as a dropbox in the tool area.

By default, they are labeled: media, message, other, presentation, spreadsheet and text, and each maps to a document category. This is determined in the [guifilters] section, where each control is defined by a variable naming a query language fragment.

A simple exemple will hopefully make things clearer.

[guifilters]

Big Books = dir:"~/My Books" size>10K
My Docs = dir:"~/My Documents"
Small Books = dir:"~/My Books" size<10K
System Docs = dir:/usr/share/doc

The above definition would create four filter checkboxes, labelled Big Books, My Docs, etc.

The text after the equal sign must be a valid query language fragment, and, when the button is checked, it will be combined with the rest of the query with an AND conjunction.

Any name text before a colon character will be erased in the display, but used for sorting. You can use this to display the checkboxes in any order you like. For exemple, the following would do exactly the same as above, but ordering the checkboxes in the reverse order.

[guifilters]

d:Big Books = dir:"~/My Books" size>10K
c:My Docs = dir:"~/My Documents"
b:Small Books = dir:"~/My Books" size<10K
a:System Docs = dir:/usr/share/doc

As you may have guessed, The default [guifilters] section looks like:

[guifilters]
text = rclcat:text
spreadsheet = rclcat:spreadsheet
presentation = rclcat:presentation
media = rclcat:media
message = rclcat:message
other = rclcat:other

The mimeview file

mimeview specifies which programs are started when you click on an Open link in a result list. Ie: HTML is normally displayed using firefox, but you may prefer Konqueror, your openoffice.org program might be named oofice instead of openoffice etc.

Changes to this file can be done by direct editing, or through the recoll GUI preferences dialog.

If Use desktop preferences to choose document editor is checked in the RCL GUI preferences, all mimeview entries will be ignored except the one labelled application/x-all (which is set to use xdg-open by default).

In this case, the xallexcepts top level variable defines a list of MIME type exceptions which will be processed according to the local entries instead of being passed to the desktop. This is so that specific RCL options such as a page number or a search string can be passed to applications that support them, such as the evince viewer.

As for the other configuration files, the normal usage is to have a mimeview inside your own configuration directory, with just the non-default entries, which will override those from the central configuration file.

All viewer definition entries must be placed under a [view] section.

The keys in the file are normally MIME types. You can add an application tag to specialize the choice for an area of the filesystem (using a localfields specification in mimeconf). The syntax for the key is mimetype|tag

The nouncompforviewmts entry, (placed at the top level, outside of the [view] section), holds a list of MIME types that should not be uncompressed before starting the viewer (if they are found compressed, ie: mydoc.doc.gz).

The right side of each assignment holds a command to be executed for opening the file. The following substitutions are performed:

  • %D.

    Document date

  • %f.

    File name. This may be the name of a temporary file if it was necessary to create one (ie: to extract a subdocument from a container).

  • %i.

    Internal path, for subdocuments of containers. The format depends on the container type. If this appears in the command line, RCL will not create a temporary file to extract the subdocument, expecting the called application (possibly a script) to be able to handle it.

  • %M.

    MIME type

  • %p.

    Page index. Only significant for a subset of document types, currently only PDF, Postscript and DVI files. Can be used to start the editor at the right page for a match or snippet.

  • %s.

    Search term. The value will only be set for documents with indexed page numbers (ie: PDF). The value will be one of the matched search terms. It would allow pre-setting the value in the “Find” entry inside Evince for example, for easy highlighting of the term.

  • %u.

    Url.

In addition to the predefined values above, all strings like %(fieldname) will be replaced by the value of the field named fieldname for the document. This could be used in combination with field customisation to help with opening the document.

The ptrans file

ptrans specifies query-time path translations. These can be useful in multiple cases.

The file has a section for any index which needs translations, either the main one or additional query indexes. The sections are named with the XAP index directory names. No slash character should exist at the end of the paths (all comparisons are textual). An exemple should make things sufficiently clear

[/home/me/.recoll/xapiandb]
/this/directory/moved = /to/this/place

[/path/to/additional/xapiandb]
/server/volume1/docdir = /net/server/volume1/docdir
/server/volume2/docdir = /net/server/volume2/docdir

Examples of configuration adjustments

Adding an external viewer for an non-indexed type

Imagine that you have some kind of file which does not have indexable content, but for which you would like to have a functional Open link in the result list (when found by file name). The file names end in .blob and can be displayed by application blobviewer.

You need two entries in the configuration files for this to work:

  • In $RECOLL_CONFDIR/mimemap (typically ~/.recoll/mimemap), add the following line:

    .blob = application/x-blobapp

    Note that the MIME type is made up here, and you could call it diesel/oil just the same.

  • In $RECOLL_CONFDIR/mimeview under the [view] section, add:

    application/x-blobapp = blobviewer %f

    We are supposing that blobviewer wants a file name parameter here, you would use %u if it liked URLs better.

If you just wanted to change the application used by RCL to display a MIME type which it already knows, you would just need to edit mimeview. The entries you add in your personal file override those in the central configuration, which you do not need to alter. mimeview can also be modified from the Gui.

Adding indexing support for a new file type

Let us now imagine that the above .blob files actually contain indexable text and that you know how to extract it with a command line program. Getting RCL to index the files is easy. You need to perform the above alteration, and also to add data to the mimeconf file (typically in ~/.recoll/mimeconf):

  • Under the [index] section, add the following line (more about the rclblob indexing script later):

    application/x-blobapp = exec rclblob

    Or if the files are mostly text and you don’t need to process them for indexing:

    application/x-blobapp = internal text/plain

  • Under the [icons] section, you should choose an icon to be displayed for the files inside the result lists. Icons are normally 64x64 pixels PNG files which live in /usr/share/recoll/images.

  • Under the [categories] section, you should add the MIME type where it makes sense (you can also create a category). Categories may be used for filtering in advanced search.

The rclblob handler should be an executable program or script which exists inside /usr/share/recoll/filters. It will be given a file name as argument and should output the text or html contents on the standard output.

The filter programming section describes in more detail how to write an input handler.