# Recoll user manual

Jean-Francois
Dockes

    jean-francois.dockes@wanadoo.fr

2005
Jean-Francois Dockes
$Id: usermanual.sgml,v 1.16 2006-09-11 14:22:15 dockes Exp $

This document introduces full text search notions and describes the installation and use of the &RCL; application.

## Introduction

### Giving it a try

If you do not like reading manuals (who does?) and would like to give &RCL; a try, just perform installation and start the `recoll` user interface, which will index your home directory by default, allowing you to search immediately after indexing completes.

Do not do this if your home has a huge number of documents and you do not want to wait or are very short on disk space. In this case, you may want to edit the configuration file first to restrict the indexed area.

Also be aware that you will need to install the appropriate supporting applications for document types that need them (for example antiword for ms-word files).

#### Full text search

&RCL; is a full text search application. Full text search applications let you find your data by content rather than by external attributes (like a file name). More specifically, they will let you specify words (terms) that should or should not appear in the text you are looking for, and 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 those terms are prominent, in a similar way to internet search engines.

&RCL; tries 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 by the search tool is probably the most important element for a search application.

In many cases, you are looking for all the forms of a word, not for a specific form or spelling. These different forms may include plurals, different tenses for a verb, or terms derived from the same root or stem (exemple: floor, floors, floored, floorings...). &RCL; will by default expand queries to all such related terms (words that reduce to the same stem). This expansion can be disabled at search time.

Stemming, by itself, does not accomodate for misspellings or phonetic searches. &RCL; currently does not support these features.

#### 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. &RCL; provides the interface to get data into (indexing) and out (searching) of the system.

In practice, &XAP; works by remembering where terms appear in your document files. The acquisition process is called indexing.

The resulting 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 the result is not nice, as all formatting, punctuation and capitalisation are lost).

&RCL; stores all internal data in Unicode UTF-8 format, and it can index files with different character sets, encodings, and languages into the same index. It has input filters for many document types.

Stemming depends on the document language. &RCL; stores the unstemmed versions of terms and uses auxiliary databases for term expansion. It can switch stemming languages, or add a language, without reindexing. Storing documents in different languages in the same index is possible, and useful in practice, but does introduce possibilities of confusion. &RCL; currently makes no attempt at automatic language recognition.

&RCL; has many parameters which define exactly what to index, and how to classify and decode the source documents. These are kept in a configuration file. A default configuration is copied into a standard location (usually something like `/usr/[local/]share/recoll/examples`) during installation. The default parameters from this file may be overriden by values that you set inside your personal configuration, found by default in the `.recoll` subdirectory 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.

Indexing is started automatically the first time you execute the `recoll` search graphical user interface, or by executing the `recollindex` command.

Searches are performed inside the `recoll` program, which has many options to help you find what you are looking for.

## 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. On the first execution, of course, all documents will need processing. A full index build can be forced later on by specifying an option to the indexing command (`recollindex -z`).

&RCL; indexing takes place at discrete times. There is currently no interface to real time file modification monitors. The typical usage is to have a nightly indexing run programmed into your `cron` file.

Side note: there is nothing in &RCL; and &XAP; that would prevent interfacing with a real time file modification monitor, but this would tend to consume significant system resources for dubious gain, because you rarely need a full text search to find documents you just modified. `recollindex -i` can be used to add individual files to the index if you want to play with this, see the manual page.

&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 mail folder files can hold many individually indexed documents.

&RCL; indexing processes plain text, HTML, openoffice and e-mail files internally. Other types (ie: postscript, pdf, ms-word, rtf) need external applications for preprocessing. The list is in the installation section.

Without further configuration, &RCL; will index all appropriate files from your home directory, with a reasonable set of defaults.

### Index storage

The default location for the index data is the `$HOME/.recoll/xapiandb/` directory. This can be changed by setting the `RECOLL_CONFDIR` environment variable, or by specifying the `dbdir` parameter in the configuration file (see the configuration section).

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 it will be quite typical nowadays (2006), that even a big index will be negligible against the total amount of data on the computer.

The index data directory only contains data that will be rebuilt by an index run, so that it can be destroyed safely.

#### Security aspects

The &RCL; index does not hold copies of the indexed documents. 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.

As of version 1.4, &RCL; will create the configuration directory with a mode of 0700 (access by owner only). As the index directory is by default a subdirectory 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, and set the directory access modes appropriately.

### The indexing configuration

Values set in the system-wide configuration file (named like `/usr/[local/]share/recoll/examples/recoll.conf`) can be overriden by those set in the personal one, named `$HOME/.recoll/recoll.conf` by default or `$RECOLL_CONFDIR/recoll.conf` if RECOLL_CONFDIR is set.

The most accurate documentation for editing the file is given by comments inside the central one. If you want to adjust the configuration before indexing, just click Cancel when the program asks if it should start initial indexing. This will have created a `.recoll` directory containing empty configuration files.

The configuration is also documented inside the installation chapter of this document, or in the recoll.conf(5) man page.

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

### Starting indexing

Indexing is performed either by the `recollindex` program, or by the indexing thread inside the `recoll` program (use the File menu).

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

It is best to avoid interrupting the indexing process, as this may sometimes leave the database in a bad state. This is not a serious problem, as you then just need to clear everything and restart the indexing: the index files are normally stored in the `$HOME/.recoll/xapiandb` directory, which you can just delete if needed. Alternatively, you can start `recollindex -z`, which will reset the database before indexing.

### 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 > /tmp/recolltrace 2>&1

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.

## Search

The `recoll` program provides the user interface for searching. It is based on the QT library.

### Simple search

1. Start the `recoll` program.

2. Possibly choose a search mode: Any term or All terms or File name.

3. Enter search term(s) in the text field at the top of the window.

4. Click the Search button or hit the Enter key to start the search.

The initial default search mode is Any term. This will look for documents with any of the search terms (the ones with more terms will get better scores). All terms will ensure that only documents with all the terms will be returned. File name will specifically look for file names, and allows using wildcards (`*`, `?` , `[]`).

&RCL; remembers the last few searches that you performed. You can use the simple search text entry widget (a combobox) to recall them (click on the thing at the right of the text field). Please note, however, that only the search texts are remembered, not the mode (all/any/filename).

You can use the Tools / Advanced search dialog for more complex searches.

After starting a search, a list of results will instantly be displayed in the main list window. Clicking on the `Preview` link for an entry will open an internal preview window for the document. Clicking the `Edit` link will attempt to start an external viewer (have a look at the `mimeconf` configuration file to see how these are configured).

By default, the document list is presented in order of relevance (how well the system estimates that the document matches the query). You can specify a different ordering by using the Tools / Sort parameters dialog.

The `Preview` and `Edit` 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 viewer for the file type. This can sometimes be adjusted simply by tweaking the `mimemap` and `mimeconf` configuration files.

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.

### Complex/advanced search

The advanced search dialog has fields that will allow a more refined search, looking for documents with all given elements, a given exact phrase, none of the given elements, or a given file name (with wildcard expansion). All relevant fields will be combined by an implicit AND clause. All fields except "Exact phrase" can accept single words, or phrases enclosed in double quotes.

It will let you search for documents of specific mime types (ie: only `text/plain`, or `text/html` or `application/pdf` etc...)

It will let you restrict the search results to a subtree of the indexed area.

Click on the Start Search button in the advanced search dialog to start the search. The button in the main window always performs a simple search.

Click on the `Show query details` link at the top of the result page to see the query expansion.

### Multiple databases

Your &RCL; configuration always defines a main index. This is what gets updated, for example, when you execute `recollindex`.

You can use the search configuration tool to define additional databases to be searched. These databases can be made active or inactive at any moment.

The typical use of this feature is for a system administrator to set up a central index, that you may choose to search, or not, in addition to your personal data. Of course, there are other possibilities.

The main index (defined by your personal configuration) is always active.

The list of searchable databases may also be defined by the `RECOLL_EXTRA_DBS` environment variable. This should hold a colon-separated list of index directories, ie:

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

### 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.

### Result list sorting

The documents in a result list are normally sorted in order of relevance. It is possible to specify different sort parameters by using the Sort parameters dialog (located in the Tools menu).

The tool sorts a specified number of the most relevant documents in the result list, according to specified criteria. The currently available criteria are date and mime type.

The sort parameters stay in effect until they are explicitely reset, or the program exits. An activated sort is indicated in the result list header.

### Additional result list functionality

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

- Preview

- Edit

- Copy File Name

- Copy Url

- Find similar

The Preview and Edit entries do the same thing as the corresponding links. The two following entries will copy either an url or the file path to the clipboard, for pasting into another application.

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.

### Search tips, shortcuts

#### 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.

#### Phrases

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 exact phrase field of the advanced search dialog to the same effect.

#### Term completion

Typing ^TAB (Control+Tab) 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 for search from displayed documents

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

#### Finding related documents

Selecting the More like this 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.

#### 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.

#### 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 abandonned as it did not seem really useful). Alternatively, you can use specific file name search which will only look for file names and can use wildcard expansion.

#### Quitting

Entering ^Q almost anywhere will close the application.

#### Closing previews

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

### Customising the search interface

It is possible to customise some aspects of the search interface by using Query configuration entry in the Preferences menu.

There are two tabs in the dialog, dealing with the interface itself, and with the parameters used for searching and returning results.

#### User interface 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 customise 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.

- Html help browser: this will let you chose your preferred browser which will be started from the Help menu to read the user manual. You can enter a simple name if the command is in your PATH, or browse for a full pathname.

- Show document type icons in result list: icons in the result list can be turned off. They take quite a lot of space and convey relatively little useful information.

- Auto-start simple search on whitespace entry: if this is checked, a search will be executed each time you enter a space in the simple search input field. This lets you look at the result list as you enter new terms. This is off by default, you may like it or not...

#### Search parameters:

- 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.

- Dynamically build abstracts: this decides if &RCL; tries to build document abstracts when displaying the result list. Abstracts are constructed by taking context from the document information, around the search terms. This can slow down result list display significantly for big documents, and you may want to turn it off.

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

#### Extra databases:

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

Once entered, the databases will appear in the All extra databases list, and you can chose which ones you want to use at any moment by tranferring them to/from the Active extra databases list.

Your main database (the one the current configuration indexes to), is always implicitely active. If this is not desirable, you can set up your configuration so that it indexes, for example, an empty directory.

## Installation

### Building from source

#### Prerequisites

At the very least, you will need to download and install the xapian core package (&RCL; development currently uses version 0.9.5), and the qt runtime and development packages (&RCL; development currently uses version 3.3.5, but any 3.3 version is probably ok).

You will most probably be able to find a binary package for qt for your system. You may have to compile &XAP; but this is not difficult (if you are using FreeBSD, there is a port).

You may also need libiconv. &RCL; currently uses version 1.9 (this should not be critical). On Linux systems, the iconv interface is part of libc and you should not need to do anything special.

##### Building

&RCL; has been built on Linux (redhat7.3, mandriva 2005, Fedora Core 3), FreeBSD and Solaris 8. If you build on another system, I would very much welcome patches.

Depending on the qt configuration on your system, you may have to set the `QTDIR` and `QMAKESPECS` variables in your environment:

- `QTDIR` should point to the directory above the one that holds the qt include files (ie: qt.h).

- `QMAKESPECS` should be set to the name of one of the qt mkspecs subdirectories (ie: linux-g++).

On many Linux systems, `QTDIR` is set by the login scripts, and `QMAKESPECS` is not needed because there is a `default` link in `mkspecs/`.

The &RCL; `configure` script does a better job of checking these variables after release 1.1.1. Before this, unexplained errors will occur during compilation if the environment is not set up. Also, for 1.1.0 the `qmake` command should be in your PATH (later releases can also find it in `$QTDIR/bin`).

Normal procedure:

            cd recoll-xxx
            configure
            make
            (practises usual hardship-repelling invocations)

There little autoconfiguration. The `configure` script will mainly link one of the system-specific files in the `mk` directory to `mk/sysconf`. If your system is not known yet, it will tell you as much, and you may want to manually copy and modify one of the existing files (the new file name should be the output of `uname -s`).

##### Installation

Either type `make install` or execute `recollinstall prefix`, 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`.

You can then proceed to configuration.

### Installing a prebuilt copy

#### Installing through a package system

If you are lucky enough to be using a port system or a prebuilt package (RPM or other), just follow the usual procedure, and have a look at the configuration section.

#### Installing a prebuilt &RCL;

The unpackaged binary versions are just compressed tar files of a build tree, where only the useful parts were kept (executables and sample configuration).

The executable binary files are built with a static link to libxapian and libiconv, to make installation easier (no dependencies). However, this also means that you cannot change the versions which are used.

After extracting the tar file, you can proceed with installation as if you had built the package from source.

### Packages needed for external file types

&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 dependencies. None is needed for building &RCL;):

- PDF: pdftotext is part of the Xpdf package.

- Postscript: pstotext.

- MS Word: antiword.

- RTF: unrtf

- dvi: dvips

- djvu: DjVuLibre

- MP3: &RCL; will use the `id3info` command from the id3lib package to extract tag information. Without it, only the filenames will be indexed.

Text, Html, mail folders and Openoffice files are processed internally.

### Configuration overview

There are two sets of configuration files. The system-wide files are kept in a directory named like `/usr/[local/]share/recoll/examples`, they define default values for the system. A parallel set of files exists by default in the `.recoll` directory in your home. This directory can be changed with the `RECOLL_CONFDIR` environment variable or the -c option parameter to `recoll` and `recollindex`.

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.

Most of the parameters specific to the `recoll` GUI are set through the Preferences menu and stored in the standard QT place (`$HOME/.qt/recollrc`). You probably do not want to edit this by hand.

For other options, &RCL; uses text configuration files. You will have to edit them by hand for now (there is still some hope for a GUI configuration tool in the future). 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.

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

            # Space-separated list of 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]).

Section lines allow redefining some parameters for a directory subtree. Some of the parameters used for indexing are looked up hierarchically from the more to the less specific. Not all parameters can be meaningfully redefined, this is specified for each in the next section.

The tilde character (~) is expanded in file names to the name of the user's home directory.

White space is used for separation inside lists. Elements with embedded spaces can be quoted using double-quotes.

#### Main configuration file

`recoll.conf` is the main configuration file. It defines things like what to index (top directories and things to ignore), and the default character set to use for document types which do not specify it internally.

The default configuration will index your home directory. If this is not appropriate, start `recoll` to create a blank configuration, click Cancel, and edit the configuration file before restarting the command. This will start the initial indexing, which may take some time.

Paramers:

`topdirs`

  Specifies the list of directories or files to index (recursively for directories). The indexer will not follow symbolic links inside the indexed trees. If an entry in the `topdirs` list is a symbolic link, indexing will not start and will generate an error.

`skippedNames`

  A space-separated list of patterns for names of files or directories that should be completely ignored. The list defined in the default file is:

      *~ #* bin CVS  Cache caughtspam  tmp

  The list can be redefined for subdirectories, but is only actually changed for the top level ones in `topdirs`.

  The top-level directories are not affected by this list (that is, a directory in `topdirs` might match and would still be indexed).

  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, mail 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` or `~/.evolution` in `topdirs`.

`loglevel`

  Verbosity level for recoll and recollindex. A value of 4 lists quite a lot of debug/information messages. 2 only lists errors.

`logfilename`

  Where the messages should go. 'stderr' can be used as a special value, and is the default.

`filtersdir`

  A directory to search for the external filter scripts used to index some types of files. The value should not be changed, except if you want to modify one of the default scripts. The value can be redefined for any subdirectory.

`indexstemminglanguages`

  A list of languages for which the stem expansion databases will be built. See recollindex(1) for possible values. You can add a stem expansion database for a different language by using `recollindex -s`, but it will be deleted during the next indexing. Only languages listed in the configuration file are permanent.

`iconsdir`

  The name of the directory where `recoll` result list icons are stored. You can change this if you want different images.

`dbdir`

  The name of the Xapian data directory. It will be created if needed when the index is initialized. If this is not an absolute path, it will be interpreted relative to the configuration directory.

`defaultcharset`

  The name of the character set used for files that do not contain a character set definition (ie: plain text files). This can be redefined for any subdirectory. If it is not set at all, the character set used is the one defined by the nls environment (LC_ALL, LC_CTYPE, LANG), or iso8859-1 if nothing is set.

`guesscharset`

  Decide if we try to guess the character set of files if no internal value is available (ie: for plain text files). This does not work well in general, and should probably not be used.

`usesystemfilecommand`

  Decide if we use the `file -i` system command as a final step for determining the mime type for a file (the main procedure uses suffix associations as defined in the `mimemap` file). This can be useful for files with suffixless names, but it will also cause the indexing of many bogus "text" files.

`indexallfilenames`

  &RCL; indexes file names in a special section of the database to allow specific file names searches using wild cards. This parameter decides if file name indexing is performed only for files with mime types that would qualify them for full text indexing, or for all files inside the selected subtrees, independant of mime type.

#### The mimemap file

`mimemap` specifies the file name extension to mime type mappings.

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

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

`mimemap` also has a `recoll_noindex` variable which is a list of suffixes. Matching files will be skipped (avoids unnecessary decompressions or `file` executions). This is partially redundant with `skippedNames` in the main configuration file, with two differences: it will not affect directories, and it can be changed for any subdirectory.

#### The mimeconf file

`mimeconf` specifies how the different mime types are handled for indexing, and for display.

Changing the indexing parameters is probably not a good idea except if you are a &RCL; developper.

You may want to adjust the external viewers defined in (ie: html is either previewed internally or displayed using firefox, but you may prefer mozilla, your openoffice.org program might be named `oofice` instead of `openoffice` ...). Look for the `[view]` section.

You can also change the icons which are displayed by `recoll` in the result lists (the values are the basenames of the png images inside the `iconsdir` directory (specified in `recoll.conf`).