                           Recoll user manual

  Jean-Francois Dockes

   <jean-francois.dockes@wanadoo.fr>

   Copyright (c) 2005 Jean-Francois Dockes

   This document introduces full text search notions and describes
   the installation and use of the Recoll application. It currently
   describes Recoll 1.9.

     --------------------------------------------------------------

   Table of Contents

   1. Introduction

                1.1. Giving it a try

                1.2. Full text search

                1.3. Recoll overview

   2. Indexing

                2.1. Introduction

                2.2. Index storage

                             2.2.1. Xapian index formats

                             2.2.2. Security aspects

                2.3. Indexing configuration

                             2.3.1. The indexing configuration GUI

                2.4. Periodic indexing

                             2.4.1. Starting indexing

                             2.4.2. Using cron to automate indexing

                2.5. Real time indexing

   3. Searching

                3.1. Simple search

                3.2. The result list

                             3.2.1. The result list right-click menu

                3.3. The preview window

                3.4. The query language

                3.5. Complex/advanced search

                3.6. The term explorer tool

                3.7. More about wildcards

                3.8. Multiple databases

                3.9. Document history

                3.10. Sorting search results

                3.11. Search tips, shortcuts

                3.12. Customizing the search interface

   4. Installation

                4.1. Installing a prebuilt copy

                             4.1.1. Installing through a package
                             system

                             4.1.2. Installing a prebuilt Recoll

                4.2. Supporting packages

                4.3. Building from source

                             4.3.1. Prerequisites

                             4.3.2. Building

                             4.3.3. Installation

                4.4. Configuration overview

                             4.4.1. Main configuration file

                             4.4.2. The mimemap file

                             4.4.3. The mimeconf file

                             4.4.4. The mimeview file

                             4.4.5. Examples of configuration
                             adjustments

                4.5. The KDE Kicker Recoll applet

                4.6. Extending Recoll

                             4.6.1. Writing a document filter

     --------------------------------------------------------------

                        Chapter 1. Introduction

1.1. Giving it a try

   If you do not like reading manuals (who does?) and would like to
   give Recoll 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 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 want to edit the configuration file
   first to restrict the indexed area.

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

     --------------------------------------------------------------

1.2. Full text search

   Recoll 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.

   Recoll 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 (example: floor, floors, floored, flooring...).
   Recoll 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 accommodate for misspellings or
   phonetic searches. Recoll supports these features through a
   specific tool (the term explorer) which will let you explore the
   set of index terms along different modes.

     --------------------------------------------------------------

1.3. Recoll overview

   Recoll uses the Xapian information retrieval library as its
   storage and retrieval engine. Xapian is a very mature package
   using a sophisticated probabilistic ranking model. Recoll provides
   the interface to get data into (indexing) and out (searching) of
   the system.

   In practice, Xapian 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. Recoll 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 capitalization are lost).

   Recoll 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. Recoll stores the
   unstemmed versions of terms and uses auxiliary databases for term
   expansion. It can switch stemming languages, or add a language,
   without re-indexing. Storing documents in different languages in
   the same index is possible, and useful in practice, but does
   introduce possibilities of confusion. Recoll currently makes no
   attempt at automatic language recognition.

   Recoll 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 overridden by values that
   you 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 Recoll 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.

     --------------------------------------------------------------

                          Chapter 2. Indexing

2.1. Introduction

   Indexing is the process by which the set of documents is analyzed
   and the data entered into the database. Recoll 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 by specifying an option to the indexing command (recollindex
   -z).

   Recoll indexing can be performed with two different methods:

     * Periodic indexing: indexing takes place at discrete times, by
       executing the recollindex command. The typical usage is to
       have a nightly indexing run programmed into your cron file.

     * Real time indexing: indexing takes place as soon as a file is
       created or changed. recollindex runs as a daemon and uses a
       file system alteration monitor such as Fam, Gamin or inotify
       do detect file changes. Monitoring a big directory tree can
       consume significant system resources.

   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, for dubious gains.

   

   Recoll 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.

   Recoll 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, Recoll will index all appropriate
   files from your home directory, with a reasonable set of defaults.

   In some cases, it may be interesting to index different areas of
   the file system to separate databases. You can do this by using
   multiple configuration directories, each indexing a file system
   area to a specific database. See the section about using multiple
   databases for more information on multiple configurations and
   indexes.

     --------------------------------------------------------------

2.2. Index storage

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

     * You can specify a different configuration directory by setting
       the RECOLL_CONFDIR environment variable, or using the -c
       option to the Recoll 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
       commands:

 export RECOLL_CONFDIR=~/.indexes-email
 recoll
          

       Then Recoll 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 that
       you wish to make searchable.

     * You can also specify a different 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 concerns.

   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 (xapiandb) only contains data that can be
   completely rebuilt by an index run, and it can always be destroyed
   safely.

     --------------------------------------------------------------

  2.2.1. Xapian index formats

   If your first installation of Recoll was 1.9.0 or more recent, you
   can skip this section.

   Xapian has had two possible index formats for quite some time. The
   "old" one named Quartz, and the new one named Flint. Xapian 0.9
   used Quartz by default, but could use Flint if a specific
   environment variable (XAPIAN_PREFER_FLINT) was set. Xapian 1.0
   still supports Quartz but will use Flint by default for new index
   creations.

   The number of disk accesses performed during indexing has been
   much optimized in the new Flint engine and you may see indexing
   times improved by 50% in some cases (compared to Quartz),
   typically for big indexes where disk accesses dominate the
   indexing time. There is also a more modest improvement of index
   size.

   Xapian will not convert automatically an existing index from the
   Quartz to the Flint format. If you have an older index and want to
   take advantage of the new format (which can be done without
   setting the environment variable as of Recoll 1.8.2 and Xapian
   1.0.0), you will have to explicitely delete the old index, then
   run a normal indexing process.

   Unfortunately, using the -z option to recollindex is not
   sufficient to change the format, you have to delete all files
   inside the index directory (typically ~/.recoll/xapiandb) before
   starting indexing.

     --------------------------------------------------------------

  2.2.2. Security aspects

   The Recoll 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, Recoll 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.

     --------------------------------------------------------------

2.3. Indexing configuration

   Variables set inside the Recoll 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
   using the dialogs in the recoll GUI.

   You can also use multiple indexes defined by separate
   configurations, typically to separate personal and shared indexes,
   or to take advantage of the organization of your data to improve
   search precision.

   The first time you start recoll, you will be asked whether or not
   you would like recoll to build the index. If you want to adjust
   the configuration before indexing, just click Cancel at this
   point. That way, recoll will have created a ~/.recoll directory
   containing empty configuration files.

   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 you may
   interested in is probably topdirs, which determines what subtrees
   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

     --------------------------------------------------------------

  2.3.1. The indexing configuration GUI

   As of Recoll 1.10, most parameters for a given indexing
   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 menu. It has two
   main panels. The first panel allows setting global variables, like
   the list of top directories or the list of skipped paths. The
   second panel allows setting variables that can be redefined for
   subdirectories. This second panel 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 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...

     --------------------------------------------------------------

2.4. Periodic indexing

  2.4.1. Starting indexing

   Indexing is performed either by the recollindex program, or by the
   indexing thread inside the recoll program (use the File menu).
   Both programs will use of the RECOLL_CONFDIR variable or accept a
   -c confdir option to specify the configuration directory to be
   used.

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

   It is best to avoid interrupting the indexing process, as this may
   sometimes leave the index in a bad state. This is not a serious
   problem, as you then just need to delete the index files 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 with option -z,
   which will reset the database before indexing.

     --------------------------------------------------------------

  2.4.2. 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.

     --------------------------------------------------------------

2.5. 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.

   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.

   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).

   Starting the daemon is normally performed as part of the user
   session script. 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
   explicitely. (The X11 server monitoring can be disabled with
   option -x to recollindex).

   Under KDE, you can place a small script to start recollindex -m
   under $HOME/.kde/Autostart. This will be executed when the session
   begins.

   There is a similar mechanism under Gnome (find the session control
   tool in the menus and use the "Startup programs" tab).

   By default, the indexing daemon will write its messages to a file
   inside the configuration directory (this is controlled by the
   daemlogfilename and daemloglevel configuration parameters). You
   may want to change this. 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.

   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. You probably do not want to enable
   it if your system is short on resources. Periodic indexing is
   adequate in most cases.

     --------------------------------------------------------------

                          Chapter 3. Searching

   The recoll program provides the 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) shas multiple entry fields, which you
       may use to build a logical condition, with additional
       filtering on file type and location in the file system.

   In most cases, you can enter the terms as you think them, even if
   they contain embedded punctuation or other non-textual characters.
   For exemple, Recoll can handle things like e-mail 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-oriental languages written with Chinese
   characters. 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).

     --------------------------------------------------------------

3.1. 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 All terms. This will look for
   documents containing all of the search terms (the ones with more
   terms will get better scores). Any term will search for documents
   where at least one of the terms appear. File name will
   specifically look for file names.

   The fourth entry (Query Language) is described in its own section.

   All search modes allow wildcards inside terms (*, ?, []). You may
   want to have a look at the section about wildcards for more
   information about this.

   You can search for exact phrases (adjacent words in a given order)
   by enclosing the input inside double quotes. Ex: "virtual
   reality".

   Character case has no influence on search, except that you can
   disable stem expansion for any term by capitalizing it. Ie: a
   search for floor will also normally look for flooring, floored,
   etc., but a search for Floor will only look for floor, in any
   character case (stemming can also be disabled globally in the
   preferences).

   Recoll 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/file name).

   Typing Esc Space while entering a word in the simple search entry
   will open a window with possible completions for the word. The
   completions are extracted from the database.

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

   Note that, apart from wildcard characters (single ? characters are
   ok), you can cut and paste any text into an All terms or Any term
   search field, punctuation, newlines and all. Recoll will process
   it and produce a meaningful search. This is what most
   differentiates this mode from the Query Language mode, where you
   have to care about the syntax.

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

     --------------------------------------------------------------

3.2. The 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 specify a different ordering by using the Tools /
   Sort parameters dialog.

   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 Edit link will attempt to start an external viewer.
   The viewers can be configured through the user preferences dialog,
   or by editing the mimeview configuration file.

   The Preview and Edit edit links may not be present for all
   entries, meaning that Recoll 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 mimeview configuration files
   (the latter can be modified with the user preferences dialog).

   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.

     --------------------------------------------------------------

  3.2.1. 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

     * Edit

     * Copy File Name

     * Copy Url

     * Find similar

     * Find similar

     * Parent document

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

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

   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.

   The Parent document entry will appear for documents which are not
   actually files but are part of, or attached to, a higher level
   document. This entry is mainly useful for email attachments and
   permits viewing the message to which the document is attached.
   Note that the entry will also appear for an email which is part of
   an mbox folder file, but that you can't actually visualize the
   folder (there will be an error dialog if you try). Recoll is
   unfortunately not yet smart enough to disable the entry in this
   case.

     --------------------------------------------------------------

3.3. 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 ^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).

   The preview tabs have an internal incremental search function. You
   initiate the search either by typing a / (slash) 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 ^Up/^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.

     --------------------------------------------------------------

3.4. The query language

   The query language processor is activated on the simple search
   entry when the search mode selector is set to Query Language.

   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).

   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. Do not enter explicit parenthesis, they are not
   supported for now.

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

   The first element in the above exemple, author:"john doe" is a
   phrase search limited to a specific field. Phrase searches are
   specified as usual by enclosing the words in double quotes. The
   field specification appears before the colon (of course this is
   not limited to phrases, author:Balzac would be ok too). Recoll
   currently manages the following 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.

     * keyword for searching the document specified keywords (few
       documents actually have any).

   As of release 1.9, the filters have the possibility to create
   other fields with arbitrary names. No standard filters use this
   possibility yet.

   There are two other elements which may be specified through the
   field syntax, but are somewhat special:

     * ext for specifying the file name extension (Ex: ext:html)

     * dir for specifying the file location (Ex:
       dir:/home/me/somedir). Please note that this is quite
       inefficient, that it may produce very slow searches, and that
       it may be worth in some cases to set up separate databases
       instead.

     * mime for specifying the mime type. This one is quite special
       because you can specify several values which will be OR'ed
       (the normal default for the language is AND). Ex:
       mime:text/plain mime:text/html. Specifying an explicit boolean
       operator or negation (-) before a mime specification is not
       supported and will produce strange results.

   The query language is currently the only way to use the Recoll
   field search capability.

   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.

   You can use the show query link at the top of the result list to
   check the exact query which was finally executed by Xapian.

     --------------------------------------------------------------

3.5. Complex/advanced search

   The advanced search dialog has a number of fields that will allow
   a more refined search. Each entry field is configurable for the
   following modes:

     * All terms.

     * Any term.

     * None of the terms.

     * Phrase (exact terms in order within an adjustable window).

     * Proximity (terms in any order within an adjustable window).

     * Filename search with wildcards.

   Additional entry fields can be created by clicking the Add clause
   button.

   You can choose that all relevant fields will be combined by either
   an AND or an OR conjunction. All types of clauses except "phrase"
   and "near" can accept a mix of single words and phrases enclosed
   in double quotes. Stemming expansion will be performed for all
   terms not beginning with a capital letter, except for terms inside
   "phrase" clauses. Wildcards will be processed everywhere.

   Advanced search will also let you search for documents of specific
   mime types (ie: only text/plain, or text/HTML or application/pdf
   etc...). The state of the file type selection can be saved as the
   default (the file type filter will not be activated at program
   start-up, but the lists will be in the restored state).

   You can also restrict the search results to a sub-tree of the
   indexed area. If you need to do this often, you may think of
   setting up multiple indexes instead, as the performance will be
   much better.

   Click on the Start Search button in the advanced search dialog, or
   type Enter in any text field 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.

     --------------------------------------------------------------

3.6. The term explorer tool

   Recoll 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 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 Recoll 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, Recoll 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 Recoll 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 200 results for wildcards and regular expressions.

   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).

     --------------------------------------------------------------

3.7. More about wildcards

   All words entered in Recoll 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 before using wildcards.

     * Using a wildcard character at the beginning of a word can make
       for a slow search because Recoll will have to scan the whole
       index term list to find the matches.

     * 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).

     --------------------------------------------------------------

3.8. Multiple databases

   Multiple Recoll databases or indexes can be created by using
   several configuration directories which are usually 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.

   A recollindex program instance can only update one specific index.

   A recoll program instance is also associated with a specific
   index, which is the one to be updated by its indexing thread, but
   it can use any number of Recoll 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. Of course, these parameters are retained
   across program executions (there are kept separately for each
   Recoll 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.

   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

   A typical 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. 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 will have much
   better performance and may be worth the trouble.

     --------------------------------------------------------------

3.9. 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.

     --------------------------------------------------------------

3.10. Sorting search results

   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 explicitly
   reset, or the program exits. An activated sort is indicated in the
   result list header.

   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.

     --------------------------------------------------------------

3.11. Search tips, shortcuts

   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.

   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 Recoll search.
   You can also disable stem expansion or change the stemming
   language in the preferences.

   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.
   Phrases can be entered along simple terms in all simple or
   advanced search entry fields (except This exact phrase).

   Browsing the result list inside a preview window (1.5). 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.

   Forced opening of a preview window (1.6). 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.

   AutoPhrases (1.5). 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.

   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 (Recoll
   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 can use wildcard expansion.

   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.

   Closing previews. Entering ^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.

   Quitting. Entering ^Q almost anywhere will close the application.

     --------------------------------------------------------------

3.12. Customizing the search interface

   It is possible to customize 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 customize the font and/or
       font size. The rest of the fonts used by Recoll are determined
       by your generic QT config (try the qtconfig command.

     * Result paragraph format string: allows you to change the
       presentation of each result list entry. This is a qt-html
       string where the following printf-like % substitutions will be
       performed:

          * %A. Abstract

          * %D. Date

          * %I. Icon image name

          * %K. Keywords (if any)

          * %L. Preview and Edit links

          * %M. Mime type

          * %N. result Number

          * %R. Relevance percentage

          * %S. Size information

          * %T. Title

          * %U. Url

       The default value for the string is:

 <img src="%I" align="left">%R %S %L &nbsp;&nbsp;<b>%T</b><br>
 %M&nbsp;%D&nbsp;&nbsp;&nbsp;<i>%U</i><br>
 %A %K
        

       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
        

       Or the clean looking:

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

       The format of the Preview and Edit links is <a href="Pdocnum">
       and <a href="Edocnum"> where docnum is what %N would print.
       This makes the title a preview link in the above format.

       Please note that, due to the way the program handles right
       mouse clicks in the result list, if the custom formatting
       results in multiple paragraphs per result, right clicks will
       only work inside the first one.

     * 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.

     * Auto-start simple search on white space 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...

     * Start with advanced search dialog open and Start with sort
       dialog open: If you use these dialogs all the time, checking
       these entries will get them to open when recoll starts.

     * Use desktop preferences to choose document editor: if this is
       checked, the xdg-open utility will be used to open files when
       you click the Edit link in the result list, instead of the
       application defined in mimeview. xdg-open will in term use
       your desktop preferences to choose an appropriate application.

   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 Recoll 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
       synthesize and display an abstract in place of an explicit
       abstract found within the document itself.

     * Synthetic abstract size: adjust to taste...

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

   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.

     --------------------------------------------------------------

                        Chapter 4. Installation

4.1. Installing a prebuilt copy

   Recoll binary packages from the Recoll web site are always linked
   statically to the Xapian libraries, and have no other
   dependencies. You will only have to check or install supporting
   applications for the file types that you want to index beyond
   text, HTML and mail files, and maybe have a look at the
   configuration section (but this may not be necessary for a quick
   test with default parameters).

     --------------------------------------------------------------

  4.1.1. Installing through a package system

   If you use a BSD-type port system or a prebuilt package (RPM or
   other), just follow the usual procedure for your system.

     --------------------------------------------------------------

  4.1.2. Installing a prebuilt Recoll

   The unpackaged binary versions on the Recoll web site 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).

   After extracting the tar file, you can proceed with installation
   as if you had built the package from source (that is, just type
   make install). The binary trees are built for installation to
   /usr/local.

     --------------------------------------------------------------

4.2. Supporting packages

   Recoll 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 Recoll):

     * Openoffice: supported natively, but needs the unzip command to
       be installed.

     * PDF: pdftotext is part of the Xpdf package.

     * Postscript: pstotext.

     * MS Word: antiword.

     * MS Excel and PowerPoint: catdoc.

     * Wordperfect files: libwpd.

     * RTF: unrtf

     * TeX: Recoll uses the untex program. Your distribution may have
       a package for it. If it doesn't, there is a copy of the source
       on the Recoll web site, because the program has no obvious
       home. The filter can also work with detex and will use it if
       it is installed.

     * dvi: dvips

     * djvu: DjVuLibre

     * MP3: Recoll will use the id3info command from the id3lib
       package to extract tag information. Without it, only the file
       names will be indexed.

     * Pictures: Recoll uses the Exiftool Perl package to extract tag
       information. Most image file formats are supported.

   Text, HTML, mail folders Openoffice and Scribus files are
   processed internally. Lyx is used to index Lyx files. Many filters
   need sed and awk.

     --------------------------------------------------------------

4.3. Building from source

  4.3.1. Prerequisites

   At the very least, you will need to download and install the
   xapian core package (Recoll 1.9 normally uses version 1.0.2, but
   any 0.9 or 1.0.x version will work too), and the qt run-time and
   development packages (Recoll 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 Xapian but this is not
   difficult (if you are using FreeBSD, there is a port).

   You may also need libiconv. Recoll 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.

     --------------------------------------------------------------

  4.3.2. Building

   Recoll has been built on Linux (redhat7.3, mandriva 2005/6, Fedora
   Core 3/4/5/6), FreeBSD 5/6, macosx, and Solaris 8. If you build on
   another system, and need to modify things, 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: if qt.h is
       /usr/local/qt/include/qt.h, QTDIR should be /usr/local/qt).

     * QMAKESPECS should be set to the name of one of the qt mkspecs
       sub-directories (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/.

   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.

   Normal procedure:

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

   There little auto-configuration. 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).

     --------------------------------------------------------------

  4.3.3. 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.

   If the installation prefix given to recollinstall is different
   from what was specified when executing configure, you will have to
   set the RECOLL_DATADIR environment variable to indicate where the
   shared data is to be found.

   You can then proceed to configuration.

     --------------------------------------------------------------

4.4. 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/.qt/recollrc). You probably do not want to edit this by
   hand.

   For other options, Recoll 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.

   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. 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 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 definitions 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.

   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.

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

     --------------------------------------------------------------

  4.4.1. 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 by default (see
           the followLinks options though).

   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. The value can have embedded
           spaces but starting or trailing spaces will be trimmed.
           You cannot use quotes here.

   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:

 skippedNames = #* bin CVS  Cache cache* caughtspam  tmp .thumbnails .svn \
              *~ recollrc

           The list can be redefined for sub-directories, 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.

   skippedPaths and daemSkippedPaths

           A space-separated list of patterns for paths of files or
           directories that should be skipped. There is no default in
           the sample configuration file, but the code always adds
           the configuration and database directories in there.

           skippedPaths is used both by batch and real time indexing.
           daemSkippedPaths can be used to specify things that should
           be indexed at startup, but not monitored.

           Example of use for skipping text files only in a specific
           directory:

 skippedPaths = ~/somedir/*.txt
              

   followLinks

           Specifies if the indexer should follow symbolic links
           while walking the file tree. 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.

   loglevel,daemloglevel

           Verbosity level for recoll and recollindex. A value of 4
           lists quite a lot of debug/information messages. 2 only
           lists errors. The daemversion is specific to the indexing
           monitor daemon.

   logfilename, daemlogfilename

           Where the messages should go. 'stderr' can be used as a
           special value, and is the default. The daemversion is
           specific to the indexing monitor daemon.

   indexstemminglanguages

           A list of languages for which the stem expansion databases
           will be built. See recollindex(1) or use the recollindex
           -l command 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.

   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 sub-directory. 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.

   maxfsoccuppc

           Maximum file system occupation before 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.

   idxflushmb

           Threshold (megabytes of new text data) where we flush from
           memory to disk index. Setting this can help control memory
           usage. A value of 0 means no explicit flushing, letting
           Xapian use its own default, which is flushing every 10000
           documents (memory usage depends on average document size).
           The default value is 10.

   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 sub-directory.

   iconsdir

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

   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
           suffix-less names, but it will also cause the indexing of
           many bogus "text" files.

   indexedmimetypes

           Recoll normally indexes any file which it knows how to
           read. This list lets you restrict the indexed mime types
           to what you specify. If the variable is unspecified or the
           list empty (the default), all supported types are
           processed.

   indexallfilenames

           Recoll 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, independently of mime type.

   idxabsmlen

           Recoll stores an abstract for each indexed file inside the
           database. 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.

   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 config" to see
           where these are installed (look for data-dir). The default
           if the variable is not set is to use your desktop national
           language environment to guess the value.

   noaspell

           If this is set, the aspell dictionary generation is turned
           off. Useful for cases where you don't need the
           functionality or when it is unusable because aspell
           crashes during dictionary generation.

   nocjk

           If this set to true, 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.

     --------------------------------------------------------------

  4.4.2. 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 (which 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 cannot be made
   dependant on the file-system location (it is a configuration-wide
   parameter). You could accomplish with skippedNames anything that
   recoll_noindex does. The latter is used mostly for things known to
   be unindexable by a given Recoll version. Having it there avoids
   cluttering the more user-oriented and locally customized
   skippedNames.

     --------------------------------------------------------------

  4.4.3. The mimeconf file

   mimeconf specifies how the different mime types are handled for
   indexing, and which icons are displayed in the recoll result
   lists.

   Changing the parameters in the [index] section is probably not a
   good idea except if you are a Recoll developer.

   The [icons] section allows you to 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).

     --------------------------------------------------------------

  4.4.4. The mimeview file

   mimeview specifies which programs are started when you click on an
   Edit 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 user preferences dialog.

   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.

   Please note that these entries must be placed under a [view]
   section.

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

     --------------------------------------------------------------

  4.4.5. Examples of configuration adjustments

    4.4.5.1. 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 Edit 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:

              application/x-blobapp = .blob
           

       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:

                  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 Recoll 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

     --------------------------------------------------------------

    4.4.5.2. 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 Recoll 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
              

     * 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/[local/]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 filter should be an executable program or script which
   exists inside /usr/[local/]share/recoll/filters. It will be given
   a file name as argument and should output the text contents in
   html format on the standard output.

   You can find more details about writing a Recoll filter in the
   section about writing filters

     --------------------------------------------------------------

4.5. The KDE Kicker Recoll applet

   The Recoll 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 Recoll launcher to the KDE panel.

   The applet is not automatically built with the main Recoll
   programs. To build it, you need to unpack the Recoll source code,
   then go to the kde/recoll_applet/ directory, and type the usual
   configure;make;make 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
   Recoll query (in query language form), and an icon which can be
   used to restrict the search to certain types of files.

     --------------------------------------------------------------

4.6. Extending Recoll

  4.6.1. Writing a document filter

   Recoll filters are executable programs which translate from a
   specific format (ie: openoffice, acrobat, etc.) to the Recoll
   indexing input format, which was chosen to be HTML.

   Recoll filters are usually shell-scripts, but this is in no way
   necessary. These programs are extremely simple and most of the
   difficulty lies in extracting the text from the native format, not
   outputting what is expected by Recoll. Happily enough, most
   document formats already have translators or text extractors which
   handle the difficult part and can be called from the filter.

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

   The RECOLL_FILTER_FORPREVIEW environment variable (values yes, no)
   tells the filter if the operation is for indexing or previewing.
   Some filters use this to output a slightly different format. This
   is not essential.

   The output HTML 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. "&" should be
   transformed into "&amp;", "<" should be transformed into "&lt;".

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

   Recoll will also make use of other header fields if they are
   present: title, description, keywords.

   As of Recoll release 1.9, filters also have the possibility to
   "invent" field names. This should be output as meta tags:

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

   In this case, a correspondance between field name and Xapian
   prefix should also be added to the mimeconf file. See the existing
   entries for inspiration. The field can then be used inside the
   query language to narrow searches.

   The easiest way to write a new filter is probably to start from an
   existing one.

     --------------------------------------------------------------
