                           Recoll user manual

  Jean-Francois Dockes

   <jfd@recoll.org>

   Copyright (c) 2005-2012 Jean-Francois Dockes

   This document introduces full text search notions and describes
   the installation and use of the Recoll application. It currently
   describes Recoll 1.17.

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

   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. Using Beagle WEB browser plugins

                2.5. Periodic indexing

                             2.5.1. Running indexing

                             2.5.2. Using cron to automate indexing

                2.6. Real time indexing

                             2.6.1. Slowing down the reindexing rate
                             for fast changing files

   3. Searching

                3.1. Searching with the Qt graphical user interface

                             3.1.1. Simple search

                             3.1.2. The default result list

                             3.1.3. The result table

                             3.1.4. The preview window

                             3.1.5. Complex/advanced search

                             3.1.6. The term explorer tool

                             3.1.7. Multiple databases

                             3.1.8. Document history

                             3.1.9. Sorting search results and
                             collapsing duplicates

                             3.1.10. Search tips, shortcuts

                             3.1.11. Customizing the search interface

                3.2. Searching with the KDE KIO slave

                             3.2.1. What's this

                             3.2.2. Searchable documents

                3.3. Searching on the command line

                3.4. The query language

                             3.4.1. Modifiers

                3.5. Anchored searches and wildcards

                             3.5.1. More about wildcards

                             3.5.2. Anchored searches

                3.6. Desktop integration

                             3.6.1. Hotkeying recoll

                             3.6.2. The KDE Kicker Recoll applet

   4. Programming interface

                4.1. Writing a document filter

                             4.1.1. Simple filters

                             4.1.2. Telling Recoll about the filter

                             4.1.3. Filter HTML output

                4.2. Field data processing

                4.3. API

                             4.3.1. Interface elements

                             4.3.2. Python interface

   5. Installation and configuration

                5.1. Installing a binary copy

                             5.1.1. Installing through a package
                             system

                             5.1.2. Installing a prebuilt Recoll

                5.2. Supporting packages

                5.3. Building from source

                             5.3.1. Prerequisites

                             5.3.2. Building

                             5.3.3. Installation

                5.4. Configuration overview

                             5.4.1. Main configuration file

                             5.4.2. The fields file

                             5.4.3. The mimemap file

                             5.4.4. The mimeconf file

                             5.4.5. The mimeview file

                             5.4.6. Examples of configuration
                             adjustments

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

                        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 install the application and start the
   recoll graphical user interface (GUI), which will ask to index
   your home directory by default, allowing you to search immediately
   after indexing completes.

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

   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.

   A search application 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 is probably the most
   important aspect when evaluating 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...).
   Search applications usually expand queries to all such related
   terms (words that reduce to the same stem) and also provide a way
   to disable this expansion if you are actually searching for a
   specific form.

   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 mechanisms and interface to get data into and out 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 is the process by which Recoll reduces words to their
   radicals so that searching does not depend, for example, on a word
   being singular or plural (floor, floors), or on a verb tense
   (flooring, floored). Because the mechanisms used for stemming
   depend on the specific grammatical rules for each language, there
   is a separate stemmer module for most common languages where
   stemming makes sense. Storing documents written in different
   languages in the same index is possible, and commonly done. In
   this situation, you can specify several stemming languages for the
   index. Recoll stores the unstemmed versions of terms in the main
   index and uses auxiliary databases for term expansion (one for
   each stemming language), which means that you can switch stemming
   languages between searches, or add a language without needing a
   full reindex. Recoll currently makes no attempt at automatic
   language recognition, which means that the stemmer will sometimes
   be applied to terms from other languages with potentially strange
   results. In practise, even if this introduces possibilities of
   confusion, this approach has been proven quite useful, and,
   awaiting the addition of an automatic language recognition module
   to Recoll, it is much less cumbersome than separating your
   documents according to what language they are written in.

   Recoll has many parameters which define exactly what to index, and
   how to classify and decode the source documents. These are kept in
   configuration files. A default configuration is copied into a
   standard location (usually something like
   /usr/[local/]share/recoll/examples) during installation. The
   default values set by the configuration files in this directory
   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,
   which can be done either by editing the text files or by using
   configuration menus in the recoll GUI

   The indexing process is started automatically the first time you
   execute the recoll GUI. Indexing can also be performed by
   executing the recollindex command.

   Searches are usually performed inside the recoll GUI, which has
   many options to help you find what you are looking for. However,
   there are other ways to perform Recoll searches: mostly a command
   line interface, a Python programming interface, a KDE KIO slave
   module, and a Ubuntu Unity Lens module.

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

                          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, 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 (or Batch) 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 inotify, Fam or Gamin
       to detect file changes.

   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.

   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 email folders or zip archives, can
   hold many individually indexed documents, which may in turn be
   themselves compound ones. Such hierarchies can go quite deep, and
   Recoll can process, for example, an ms-word document stored as an
   attachment to an email message inside an email folder archived in
   a zip file...

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

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

   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.

   In the rare case where the index becomes corrupted (which can
   signal itself by weird search results or crashes), the index files
   need to be erased before restarting a clean indexing pass. Just
   delete the xapiandb directory (see next section), or,
   alternatively, start the next recollindex with the -z option,
   which will reset the database before indexing.

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

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 document set size, 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 nowadays (2012), typically, 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 (as long as the original
   documents exist), and it can always be destroyed safely.

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

  2.2.1. Xapian index formats

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

   Xapian will not convert automatically an existing index from the
   older format to the newer one. If you want to upgrade to the new
   format, or if a very old index needs to be converted because its
   format is not supported any more, you will have to explicitly
   delete the old index, then run a normal indexing process.

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

   Recoll (since version 1.4) 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 it to build the index. If you want to adjust the
   configuration before indexing, just click Cancel at this point,
   which will get you into the configuration interface. If you exit
   at this point, recoll will have created a ~/.recoll directory
   containing empty configuration files, which you can edit by hand.

   The configuration is documented inside the installation chapter of
   this document, or in the recoll.conf(5) man page, but the most
   current information will most likely be the comments inside the
   sample file. The most immediately useful variable 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

   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->Indexing
   Configuration menu entry. It is divided in three tabs, Global
   parameters, Local parameters, and Beagle web history, which is
   explained in the next section.

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

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

   The 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. Using Beagle WEB browser plugins

   Beagle is (was?) a concurrent desktop indexer, built on Lucene and
   the Mono project (C#), for which a number of add-on browser
   plugins were written. These work by copying visited web pages to
   an indexing queue directory, which the indexer then processes.
   Especially, there is a Firefox extension.

   If, for any reason, you so happen to prefer Recoll to Beagle, you
   can still use the Firefox plugin, which is written in Javascript
   and completely independant of C#, Beagle, Lucene..., and set
   Recoll to process the Beagle queue directory. This supposes that
   Beagle is not running, else both programs will fight for the same
   files.

   This feature can be enabled in the GUI indexing configuration
   panel, or by editing the configuration file (set
   processbeaglequeue to 1).

   There are more recent instructions about how to find and install
   the Firefox extension on the Recoll wiki.

   Unfortunately, it seems that the plugin does not work anymore with
   recent Firefox versions (tried with 10.0). This is not the trival
   installation version check issue, explicit manual indexing
   requests still work, but automatic indexing on page load does not.

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

2.5. Periodic indexing

  2.5.1. Running indexing

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

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

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

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

   recollindex has a number of other options which are described in
   its man page.

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

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

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

  2.5.2. 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 > /some/tmp/dir/recolltrace 2>&1

   Or, using anacron:

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

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

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

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

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

2.6. 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.

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

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

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

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

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

 fvwm 

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

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

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

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

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

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

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

  2.6.1. Slowing down the reindexing rate for fast changing files

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

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

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

                          Chapter 3. Searching

3.1. Searching with the Qt graphical user interface

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

   recoll has two search modes:

     * Simple search (the default, on the main screen) has a single
       entry field where you can enter multiple words.

     * Advanced search (a panel accessed through the Tools menu or
       the toolbox bar icon) has multiple entry fields, which you may
       use to build a logical condition, with additional filtering on
       file type 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 example, Recoll can handle things like email addresses, or
   arbitrary cut and paste from another text window, punctation and
   all.

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

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

  3.1.1. Simple search

    1. Start the recoll program.

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

    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 Query language. Without special
   directives, this will look for documents containing all of the
   search terms (the ones with more terms will get better scores),
   just like the All terms mode which will ignore such directives.
   Any term will search for documents where at least one of the terms
   appear.

   The Query Language features are described in a separate section.

   File name will specifically look for file names. The entry will be
   split at white space characters, and each fragment will be
   separately expanded, then the search will be for file names
   matching all fragments (this is new in 1.15, older releases did an
   OR of the whole thing which did not make sense). Things to know:

     * The search is case- and accent-insensitive.

     * Fragments without any wild card character and not capitalized
       will be prepended and appended with '*' (ie: etc -> *etc*, but
       Etc -> etc). Of course it does not make sense to have multiple
       fragments if one of them is capitalized (as this one will
       require an exact match).

     * If you want to search for a pattern including white space, use
       double quotes (ie: "admin note*").

     * If you have a big index (many files), excessively generic
       fragments may result in inefficient searches.

     * As an example, inst recoll would match recollinstall.in (and
       quite a few others...).

   The point of having a separate file name search is that wild card
   expansion can be performed more efficiently on a relatively small
   subset of the index (allowing wild cards on the left of terms
   without excessive penality).

   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.

   You can cut and paste any text into an All terms or Any term
   search field, punctuation, newlines and all - except for wildcard
   characters (single ? characters are ok). 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.

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

  3.1.2. The default result list

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

   By default, the document list is presented in order of relevance
   (how well the system estimates that the document matches the
   query). You can sort the result by ascending or descending date by
   using the vertical arrows in the toolbar (the old sort tool is
   gone after release 1.15, because the new result table has much
   better capability).

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

   Clicking the Open link will attempt to start an external viewer.
   The viewer for each document type can be configured through the
   user preferences dialog, or by editing the mimeview configuration
   file. You can also check the Use desktop preferences option in the
   user preferences dialog to use the desktop defaults for all
   documents. This is probably the best option if you are using a
   well configured Gnome or KDE desktop.

   The Preview and Open 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 editor 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).

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

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

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

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

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

    3.1.2.1. 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

     * Open

     * Copy File Name

     * Copy Url

     * Save to File

     * Find similar

     * Preview Parent document

     * Open Parent document

   The Preview and Open 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.

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

   The 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 entries 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. In other cases, the Open option makes sense, for example to
   start a chm viewer on the parent document for a help page.

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

  3.1.3. The result table

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

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

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

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

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

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

  3.1.4. The preview window

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

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

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

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

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

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

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

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

   A right-click menu in the text area allows switching between
   displaying the main text or the contents of fields associated to
   the document (ie: author, abtract, etc.). This is especially
   useful in cases where the term match did not occur in the main
   text but in one of the fields.

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

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

  3.1.5. Complex/advanced search

   The advanced search dialog helps you build more complex queries
   without memorizing the search language constructs. It can be
   opened through the Tools menu or through the main toolbar.

   The dialog has two tabs:

    1. The first tab lets you specify terms to search for, and
       permits specifying multiple clauses which are combined to
       build the search.

    2. The second tab lets filter the results according to file size,
       date of modification, mime type, or location.

   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.

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

    3.1.5.1. Avanced search: the "find" tab

   This part of the dialog lets you constructc a query by combining
   multiple clauses of different types. 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.

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

   When searching, the non-empty clauses will be combined either with
   an AND or an OR conjunction, depending on the choice made on the
   left (All clauses or Any clause).

   Entries of all types except "Phrase" and "Near" accept a mix of
   single words and phrases enclosed in double quotes. Stemming and
   wildcard expansion will be performed as for simple search.

   Phrases and Proximity searches. These two clauses work in similar
   ways, with the difference that proximity searches do not impose an
   order on the words. In both cases, an adjustable number (slack) of
   non-matched words may be accepted between the searched ones (use
   the counter on the left to adjust this count). For phrases, the
   default count is zero (exact match). For proximity it is ten
   (meaning that two search terms, would be matched if found within a
   window of twelve words). Examples: a phrase search for quick fox
   with a slack of 0 will match quick fox but not quick brown fox.
   With a slack of 1 it will match the latter, but not fox quick. A
   proximity search for quick fox with the default slack will match
   the latter, and also a fox is a cunning and quick animal.

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

    3.1.5.2. Avanced search: the "filter" tab

   This part of the dialog has several sections which allow filtering
   the results of a search according to a number of criteria

     * The first section allows filtering by dates of last
       modification. You can specify both a minimum and a maximum
       date. The initial values are set according to the oldest and
       newest documents found in the index.

     * The next section allows filtering the results by file size.
       There are two entries for minimum and maximum size. Enter
       decimal numbers. You can use suffix multipliers: k/K, m/M,
       g/G, t/T for 1E3, 1E6, 1E9, 1E12 respectively.

     * The next section allows filtering the results by their mime
       types, or mime categories (ie: media/text/message/etc.).

       You can transfer the types between two boxes, to define which
       will be included or excluded by the search.

       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).

     * The bottom section allows restricting the search results to a
       sub-tree of the indexed area. You can use the Invert checkbox
       to search for files not in the sub-tree instead. If you use
       directory filtering often and on big subsets of the file
       system, you may think of setting up multiple indexes instead,
       as the performance may be better.

       You can use relative/partial paths for filtering. Ie, entering
       dirA/dirB would match either /dir1/dirA/dirB/myfile1 or
       /dir2/dirA/dirB/someother/myfile2.

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

  3.1.6. 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).

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

  3.1.7. 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.

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

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

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

  3.1.8. 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.

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

  3.1.9. Sorting search results and collapsing duplicates

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

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

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

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

  3.1.10. Search tips, shortcuts

    3.1.10.1. Terms and search expansion

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

   Picking up new terms from result or preview text. Double-clicking
   on a word in the result list or in a preview window will copy it
   to the simple search entry field.

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

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

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

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

   File names. File names are added as terms during indexing, and you
   can specify them as ordinary terms in normal search fields (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 may be faster than the generic search especially
   when using wildcards.

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

    3.1.10.2. Working with phrases and proximity

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

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

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

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

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

    3.1.10.3. Others

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

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

   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.

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

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

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

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

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

   Quitting. Entering Ctrl-Q almost anywhere will close the
   application.

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

  3.1.11. Customizing the search interface

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

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

   User interface parameters:

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

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

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

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

     * Use <PRE> tags instead of <BR> to display plain text as HTML
       in preview: when displaying plain text inside the preview
       window, Recoll tries to preserve some of the original text
       line breaks and indentation. It can either use PRE HTML tags,
       which will well preserve the indentation but will force
       horizontal scrolling for long lines, or use BR tags to break
       at the original line breaks, which will let the editor
       introduce other line breaks according to the window width, but
       will lose some of the original indentation.

     * 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 Open 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.

     * Choose editor applications this will let you choose the
       command started by the Open links inside the result list, for
       specific document types.

     * Display category filter as toolbar... this will let you choose
       if the document categories are displayed as a list or a set of
       buttons.

     * 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.

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

   Result list parameters:

     * Number of results in a result page

     * Result list font: There is quite a lot of information shown in
       the result list, and you may want to customize the font and/or
       font size. The rest of the fonts used by Recoll are determined
       by your generic Qt config (try the qtconfig command).

     * Edit result list paragraph format string: allows you to change
       the presentation of each result list entry. See the result
       list customisation section.

     * Edit result page html header insert: allows you to define text
       inserted at the end of the result page html header. More
       detail in the result list customisation section.

     * Date format: allows specifying the format used for displaying
       dates inside the result list. This should be specified as an
       strftime() string (man strftime).

     * Abstract snippet separator: for synthetic abstracts built from
       index data, which are usually made of several snippets from
       different parts of the document, this defines the snippet
       separator, an ellipsis by default.

   Search parameters:

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

     * Stemming language: stemming obviously depends on the
       document's language. This listbox will let you chose among the
       stemming databases which were built during indexing (this is
       set in the main configuration file), or later added with
       recollindex -s (See the recollindex manual). Stemming
       languages which are dynamically added will be deleted at the
       next indexing pass unless they are also added in the
       configuration file.

     * Automatically add phrase to simple searches: a phrase will be
       automatically built and added to simple searches when looking
       for Any terms. This will give a relevance boost to the results
       where the search terms appear as a phrase (consecutive and in
       order).

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

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

     * Dynamically build abstracts: this decides if 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.

     * Synthetic abstract size: adjust to taste...

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

     * Query language magic file name suffixes: a list of words which
       automatically get turned into ext:xxx file name suffix clauses
       when starting a query language query (ie: doc xls xlsx...).
       This will save some typing for people who use file types a lot
       when querying.

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

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

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

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

    3.1.11.1. The result list format

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

     * The paragraph format

     * Html code inside the header section

   These can be edited from the Result list tab of the Query
   configuration.

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

   No more detail will be given about the header part (only useful
   with the WebKit build), if there are restrictions to what you can
   do, they are beyond this author's HTML/CSS/Javascript abilities...
   There are a few examples on the page about customising the result
   list on the Recoll web site.

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

      3.1.11.1.1. The paragraph format

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

     * %A. Abstract

     * %D. Date

     * %I. Icon image name. This is normally determined from the mime
       type. The associations are defined inside the mimeconf
       configuration file. If a thumbnail for the file is found at
       the standard Freedesktop location, this will be displayed
       instead.

     * %K. Keywords (if any)

     * %L. Precooked Preview and Edit links

     * %M. Mime type

     * %N. result Number inside the result page

     * %R. Relevance percentage

     * %S. Size information

     * %T. Title or Filename if not set.

     * %t. Title or Filename if not set.

     * %U. Url

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

   In addition to the predefined values above, all strings like
   %(fieldname) will be replaced by the value of the field named
   fieldname for this document. Only stored fields can be accessed in
   this way, the value of indexed but not stored fields is not known
   at this point in the search process (see field configuration).
   There are currently very few fields stored by default, apart from
   the values above (only author and filename), so this feature will
   need some custom local configuration to be useful. For example,
   you could look at the fields for the document types of interest
   (use the right-click menu inside the preview window), and add what
   you want to the list of stored fields. A candidate example would
   be the recipient field which is generated by the message filters.

   The default value for the paragraph format 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>&nbsp;%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
        

   Note that the P%N link in the above paragraph makes the title a
   preview link.

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

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

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

3.2. Searching with the KDE KIO slave

  3.2.1. What's this

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

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

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

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

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

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

  3.2.2. Searchable documents

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

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

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

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

3.3. Searching on the command line

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

     * By passing option -t to the recoll program.

     * By using the recollq program.

     * By writing a custom Python program, using the Recoll Python
       API.

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

   recollq is not built by default. You can use the Makefile in the
   query directory to build it. This is a very simple program, and if
   you can program a little c++, you may find it useful to taylor its
   output format to your needs.

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

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

   Sample execution:

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

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

3.4. The query language

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

   The language is roughly based on the (seemingly defunct) Xesam
   user search language specification.

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

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

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

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

   An element is composed of an optional field specification, and a
   value, separated by a colon. Example: Beatles, author:balzac,
   dc:title:grandet

   The colon, if present, means "contains". Xesam defines other
   relations, which are not supported for now.

   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 element preceded by a - specifies a term that should not
   appear. Pure negative queries are forbidden.

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

   Modifiers can be set on a phrase clause, for example to specify a
   proximity search (unordered). See the modifier section.

   Recoll currently manages the following default fields:

     * title, subject or caption are synonyms which specify data to
       be searched for in the document title or subject.

     * author or from for searching the documents originators.

     * recipient or to for searching the documents recipients.

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

     * filename for the document's file name.

     * ext specifies the file name extension (Ex: ext:html)

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

     * dir for filtering the results on file location (Ex:
       dir:/home/me/somedir). -dir also works to find results out of
       the specified directory, only after release 1.15.8. A tilde
       inside the value will be expanded to the home directory. dir
       is not a regular field and only one value makes sense in a
       query (you can't use dir:dir1 OR dir:dir2). Relative paths
       make sense, for example, dir:share/doc would match either
       /usr/share/doc or /usr/local/share/doc

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

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

          * 2001-03-01/2002-05-01 the basic syntax for an interval of
            dates.

          * 2001-03-01/P1Y2M the same specified with a period.

          * 2001/ from the beginning of 2001 to the latest date in
            the index.

          * 2001 the whole year of 2001

          * P2D/ means 2 days ago up to now if there are no documents
            with dates in the future.

          * /2003 all documents from 2003 or older.

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

     * mime or format for specifying the mime type. 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 before a mime specification is not supported and will
       produce strange results. You can filter out certain types by
       using negation (-mime:some/type), and you can use wildcards in
       the value (mime:text/*). Note that mime is the ONLY field with
       an OR default. You do need to use OR with ext terms for
       example.

     * type or rclcat for specifying the category (as in
       text/media/presentation/etc.). The classification of mime
       types in categories is defined in the Recoll configuration
       (mimeconf), and can be modified or extended. The default
       category names are those which permit filtering results in the
       main GUI screen. Categories are OR'ed like mime types above.
       This can't be negated with - either.

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

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

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

  3.4.1. Modifiers

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

     * l can be used to turn off stemming (mostly makes sense with p
       because stemming is off by default for phrases).

     * o can be used to specify a "slack" for phrase and proximity
       searches: the number of additional terms that may be found
       between the specified ones. If o is followed by an integer
       number, this is the slack, else the default is 10.

     * p can be used to turn the default phrase search into a
       proximity one (unordered). Example:"order any in"p

     * A weight can be specified for a query element by specifying a
       decimal value at the start of the modifiers. Example:
       "Important"2.5.

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

3.5. Anchored searches and wildcards

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

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

  3.5.1. 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).

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

  3.5.2. Anchored searches

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

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

 "^someterm"o10

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

   This feature can also be used with an actual phrase search, but in
   this case, the distance applies to the whole phrase and anchor, so
   that, for example, bla bla my unexpected term at the beginning of
   the text would be a match for "^my term"o5.

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

3.6. Desktop integration

   Being independant of the desktop type has its drawbacks: Recoll
   desktop integration is minimal. Here follow a few things that may
   help.

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

  3.6.1. Hotkeying recoll

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

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

  3.6.2. 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, nor is it included with the main source distribution
   (because the KDE build boilerplate makes it relatively big). You
   can download its source from the recoll.org download page. Use the
   omnipotent configure;make;make install incantation to build and
   install.

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

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

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

                    Chapter 4. Programming interface

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

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

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

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

4.1. 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 may be text/plain or text/html.

   As of Recoll 1.13, there are two kinds of filters:

     * Simple filters (the old ones) run once and exit. They can be
       bare programs like antiword, or shell-scripts using other
       programs. They are very simple to write, just having to write
       the text to the standard output.

     * Multiple filters, new in 1.13, run as long as their master
       process (ie: recollindex) is active. They can process multiple
       files (sparing the process startup time which can be very
       significant), or multiple documents per file (ie: for zip or
       chm files). They communicate with the indexer through a simple
       protocol, but are nevertheless a bit more complicated than the
       older kind. Most of these new filters are written in Python,
       using a common module to handle the protocol.

   The following will just describe the simple filters. If you can
   program and want to write one of the other kind, it shouldn't be
   too difficult to make sense of one of the existing modules. For
   example, look at rclzip which uses Zip file paths as internal
   identifiers (ipath), and rclinfo, which uses an integer index.

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

  4.1.1. Simple filters

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

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

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

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

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

   Don't forget to make your filter executable before testing !

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

  4.1.2. Telling Recoll about the filter

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

   The association of files to mime types is mostly based on name
   suffixes. The types are defined inside the mimemap file. Example:

 
.doc = application/msword

   If no suffix association is found for the file name, Recoll will
   try to execute the file -i command to determine a mime type.

   The association of file types to filters is performed in the
   mimeconf file. A sample will probably be of better help than a
   long explanation:

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

 application/ogg = exec rclogg

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

 application/x-chm = execm rclchm

   The fragment specifies that:

     * application/msword files are processed by executing the
       antiword program, which outputs text/plain encoded in utf-8.

     * application/ogg files are processed by the rclogg script, with
       default output type (text/html, with encoding specified in the
       header, or utf-8 by default).

     * text/rtf is processed by unrtf, which outputs text/html. The
       iso-8859-1 encoding is specified because it is not the utf-8
       default, and not output by unrtf in the HTML header section.

     * application/x-chm is processed by a persistant filter. This is
       determined by the execm keyword.

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

  4.1.3. Filter HTML output

   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;".
   This is not always properly done by translating programs which
   output HTML, and of course nerver by those which output plain
   text.

   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.

   Filters also have the possibility to "invent" field names. This
   should be output as meta tags:

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

   See the following section for details about configuring how field
   data is processed by the indexer.

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

4.2. Field data processing

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

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

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

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

   Fields can be:

     * indexed, meaning that their terms are separately stored in
       inverted lists (with a specific prefix), and that a
       field-specific search is possible.

     * stored, meaning that their value is recorded in the index data
       record for the document, and can be returned and displayed
       with search results.

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

   You can find more information in the section about the fields
   file, or in comments inside the file.

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

4.3. API

  4.3.1. Interface elements

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

   udi

           An udi (unique document identifier) identifies a document.
           Because of limitations inside the index engine, it is
           restricted in length (to 200 bytes), which is why a
           regular URI cannot be used. The structure and contents of
           the udi is defined by the application and opaque to the
           index engine. For example, the internal file system
           indexer uses the complete document path (file path +
           internal path), truncated to length, the suppressed part
           being replaced by a hash value.

   ipath

           This data value (set as a field in the Doc object) is
           stored, along with the URL, but not indexed by Recoll. Its
           contents are not interpreted, and its use is up to the
           application. For example, the Recoll internal file system
           indexer stores the part of the document access path
           internal to the container file (ipath in this case is a
           list of subdocument sequential numbers). url and ipath are
           returned in every search result and permit access to the
           original document.

   Stored and indexed fields

           The fields file inside the Recoll configuration defines
           which document fields are either "indexed" (searchable),
           "stored" (retrievable with search results), or both.

   Data for an external indexer, should be stored in a separate
   index, not the one for the Recoll internal file system indexer,
   except if the latter is not used at all). The reason is that the
   main document indexer purge pass would remove all the other
   indexer's documents, as they were not seen during indexing. The
   main indexer documents would also probably be a problem for the
   external indexer purge operation.

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

  4.3.2. Python interface

    4.3.2.1. Introduction

   Recoll versions after 1.11 define a Python programming interface,
   both for searching and indexing.

   The Python interface is not built by default and can be found in
   the source package, under python/recoll.

   In order to build the module, you should first build or re-build
   the Recoll library using position-independant objects:

   cd recoll-xxx/
   configure --enable-pic
   make

   There is no significant disadvantage in using PIC objects for the
   main Recoll executables, so you can use the --enable-pic option
   for the main build too.

   The python/recoll/ directory contains the usual setup.py script
   which you can then use to build and install the module:

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

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

    4.3.2.2. Interface manual

   NAME
       recoll - This is an interface to the Recoll full text indexer.

   FILE
       /usr/local/lib/python2.5/site-packages/recoll.so

   CLASSES
           Db
           Doc
           Query
           SearchData
       
       class Db(__builtin__.object)
        |  Db([confdir=None], [extra_dbs=None], [writable = False])
        |  
        |  A Db object holds a connection to a Recoll index. Use the connect()
        |  function to create one.
        |  confdir specifies a Recoll configuration directory (default: 
        |   $RECOLL_CONFDIR or ~/.recoll).
        |  extra_dbs is a list of external databases (xapian directories)
        |  writable decides if we can index new data through this connection
        |  
        |  Methods defined here:
        |  
        |  
        |  addOrUpdate(...)
        |      addOrUpdate(udi, doc, parent_udi=None) -> None
        |      Add or update index data for a given document
        |      The udi string must define a unique id for the document. It is not
        |      interpreted inside Recoll
        |      doc is a Doc object
        |      if parent_udi is set, this is a unique identifier for the
        |      top-level container (ie mbox file)
        |  
        |  delete(...)
        |      delete(udi) -> Bool.
        |      Purge index from all data for udi. If udi matches a container
        |      document, purge all subdocs (docs with a parent_udi matching udi).
        |  
        |  makeDocAbstract(...)
        |      makeDocAbstract(Doc, Query) -> string
        |      Build and return 'keyword-in-context' abstract for document
        |      and query.
        |  
        |  needUpdate(...)
        |      needUpdate(udi, sig) -> Bool.
        |      Check if the index is up to date for the document defined by udi,
        |      having the current signature sig.
        |  
        |  purge(...)
        |      purge() -> Bool.
        |      Delete all documents that were not touched during the just finished
        |      indexing pass (since open-for-write). These are the documents for
        |      the needUpdate() call was not performed, indicating that they no
        |      longer exist in the primary storage system.
        |  
        |  query(...)
        |      query() -> Query. Return a new, blank query object for this index.
        |  
        |  setAbstractParams(...)
        |      setAbstractParams(maxchars, contextwords).
        |      Set the parameters used to build 'keyword-in-context' abstracts
        |  
        |  ----------------------------------------------------------------------
        |  Data and other attributes defined here:
        |  
       
       class Doc(__builtin__.object)
        |  Doc()
        |  
        |  A Doc object contains index data for a given document.
        |  The data is extracted from the index when searching, or set by the
        |  indexer program when updating. The Doc object has no useful methods but
        |  many attributes to be read or set by its user. It matches exactly the
        |  Rcl::Doc c++ object. Some of the attributes are predefined, but, 
        |  especially when indexing, others can be set, the name of which will be
        |  processed as field names by the indexing configuration.
        |  Inputs can be specified as unicode or strings.
        |  Outputs are unicode objects.
        |  All dates are specified as unix timestamps, printed as strings
        |  Predefined attributes (index/query/both):
        |   text (index): document plain text
        |   url (both)
        |   fbytes (both) optional) file size in bytes
        |   filename (both)
        |   fmtime (both) optional file modification date. Unix time printed 
        |      as string
        |   dbytes (both) document text bytes
        |   dmtime (both) document creation/modification date
        |   ipath (both) value private to the app.: internal access path
        |      inside file
        |   mtype (both) mime type for original document
        |   mtime (query) dmtime if set else fmtime
        |   origcharset (both) charset the text was converted from
        |   size (query) dbytes if set, else fbytes
        |   sig (both) app-defined file modification signature. 
        |      For up to date checks
        |   relevancyrating (query)
        |   abstract (both)
        |   author (both)
        |   title (both)
        |   keywords (both)
        |  
        |  Methods defined here:
        |  
        |  
        |  ----------------------------------------------------------------------
        |  Data and other attributes defined here:
        |  
       
       class Query(__builtin__.object)
        |  Recoll Query objects are used to execute index searches. 
        |  They must be created by the Db.query() method.
        |  
        |  Methods defined here:
        |  
        |  
        |  execute(...)
        |      execute(query_string, stemming=1|0)
        |      
        |      Starts a search for query_string, a Recoll search language string
        |      (mostly Xesam-compatible).
        |      The query can be a simple list of terms (and'ed by default), or more
        |      complicated with field specs etc. See the Recoll manual.
        |  
        |  executesd(...)
        |      executesd(SearchData)
        |      
        |      Starts a search for the query defined by the SearchData object.
        |  
        |  fetchone(...)
        |      fetchone(None) -> Doc
        |      
        |      Fetches the next Doc object in the current search results.
        |  
        |  sortby(...)
        |      sortby(field=fieldname, ascending=true)
        |      Sort results by 'fieldname', in ascending or descending order.
        |      Only one field can be used, no subsorts for now.
        |      Must be called before executing the search
        |  
        |  ----------------------------------------------------------------------
        |  Data descriptors defined here:
        |  
        |  next
        |      Next index to be fetched from results. Normally increments after
        |      each fetchone() call, but can be set/reset before the call effect
        |      seeking. Starts at 0
        |  
        |  ----------------------------------------------------------------------
        |  Data and other attributes defined here:
        |  
       
       class SearchData(__builtin__.object)
        |  SearchData()
        |  
        |  A SearchData object describes a query. It has a number of global
        |  parameters and a chain of search clauses.
        |  
        |  Methods defined here:
        |  
        |  
        |  addclause(...)
        |      addclause(type='and'|'or'|'excl'|'phrase'|'near'|'sub',
        |                qstring=string, slack=int, field=string, stemming=1|0,
        |                subSearch=SearchData)
        |      Adds a simple clause to the SearchData And/Or chain, or a subquery
        |      defined by another SearchData object
        |  
        |  ----------------------------------------------------------------------
        |  Data and other attributes defined here:
        |  

   FUNCTIONS
       connect(...)
           connect([confdir=None], [extra_dbs=None], [writable = False])
                    -> Db.
           
           Connects to a Recoll database and returns a Db object.
           confdir specifies a Recoll configuration directory
           (the default is built like for any Recoll program).
           extra_dbs is a list of external databases (xapian directories)
           writable decides if we can index new data through this connection

   

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

    4.3.2.3. Example code

   The following sample would query the index with a user language
   string. See the python/samples directory inside the Recoll source
   for other examples.

 #!/usr/bin/env python
 import recoll

 db = recoll.connect()
 db.setAbstractParams(maxchars=80, contextwords=2)

 query = db.query()
 nres = query.execute("some user question")
 print "Result count: ", nres
 if nres > 5:
     nres = 5
 while query.next >= 0 and query.next < nres:
     doc = query.fetchone()
     print query.next
     for k in ("title", "size"):
         print k, ":", getattr(doc, k).encode('utf-8')
     abs = db.makeDocAbstract(doc, query).encode('utf-8')
     print abs
     print
 

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

               Chapter 5. Installation and configuration

5.1. Installing a binary copy

   There are three types of binary Recoll installations:

     * Through your system normal software distribution framework
       (ie, Debian/Ubuntu apt, FreeBSD ports, etc.).

     * From a package downloaded from the Recoll web site.

     * From a prebuilt tree downloaded from the Recoll web site.

   In all cases, the strict software dependancies (ie on Xapian or
   iconv) will be automatically satisfied, you should not have to
   worry about them.

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

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

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

  5.1.1. Installing through a package system

   If you use a BSD-type port system or a prebuilt package (DEB, RPM,
   manually or through the system software configuration utility),
   just follow the usual procedure for your system.

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

  5.1.2. 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.

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

5.2. 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 optional dependencies. None is needed
   for building or running Recoll except for indexing their specific
   file type).

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

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

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

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

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

   Now for the list:

     * Openoffice files need unzip and xsltproc.

     * PDF files need pdftotext which is part of the Xpdf or Poppler
       packages.

     * Postscript files need pstotext. The original version has an
       issue with shell character in file names, which is corrected
       in recent packages. See the the Recoll helper applications
       page for more detail.

     * MS Word needs antiword. It is also useful to have wvWare
       installed as it may be be used as a fallback for some files
       which antiword does not handle.

     * MS Excel and PowerPoint need catdoc.

     * MS Open XML (docx) needs xsltproc.

     * Wordperfect files need wpd2html from the libwpd (or
       libwpd-tools on Ubuntu) package.

     * RTF files need unrtf, which, in its standard version, has much
       trouble with non-western character sets. Check the Recoll
       helper applications page.

     * TeX files need untex or detex. Check the Recoll helper
       applications page for sources if it's not packaged for your
       distribution.

     * dvi files need dvips.

     * djvu files need djvutxt and djvused from the DjVuLibre
       package.

     * Audio files: Recoll releases before 1.13 used the id3info
       command from the id3lib package to extract mp3 tag
       information, metaflac (standard flac tools) for flac files,
       and ogginfo (vorbis tools) for ogg files. Releases 1.14 and
       later use a single Python filter based on mutagen for all
       audio file types.

     * Pictures: Recoll uses the Exiftool Perl package to extract tag
       information. Most image file formats are supported. Note that
       there may not be much interest in indexing the technical tags
       (image size, aperture, etc.). This is only of interest if you
       store personal tags or textual descriptions inside the image
       files.

     * chm: files in microsoft help format need Python and the pychm
       module (which needs chmlib).

     * ICS: up to Recoll 1.13, iCalendar files need Python and the
       icalendar module. icalendar is not needed for newer versions,
       which use internal code.

     * Zip archives need Python (and the standard zipfile module).

     * Rar archives need Python, the rarfile Python module and the
       unrar utility.

     * Midi karaoke files need Python and the Midi module

     * Konqueror webarchive format with Python (uses the Tarfile
       module).

     * mimehtml web archive format (support based on the email
       filter, which introduces some mild weirdness, but still
       usable).

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

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

5.3. Building from source

  5.3.1. Prerequisites

   C++ compiler. Up to Recoll version 1.13.04, its absence can
   manifest itself by strange messages about a missing iconv_open.

   Development files for Xapian core.

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

   Development files for Qt .

   Development files for X11 and zlib.

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

   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.

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

  5.3.2. Building

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

   Depending on the Qt 3 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/.

   Neither QTDIR nor QMAKESPECS should be needed with Qt 4,
   configuration details are entirely determined by qmake (which is
   quite often installed as qmake-qt4).

   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.

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

     * --enable-xattr will enable code to fetch data from file
       extended attributes. This is only useful is some application
       stores data in there, and also needs some simple configuration
       (see comments in the fields configuration file).

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

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

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

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

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

   Normal procedure:

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

   There is 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).

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

  5.3.3. 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 either the system default or the value which was specified
   when executing configure (as in configure --prefix /some/path),
   you will have to set the RECOLL_DATADIR environment variable to
   indicate where the shared data is to be found (ie for (ba)sh:
   export RECOLL_DATADIR=/some/path/share/recoll).

   You can then proceed to configuration.

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

5.4. 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/.config/Recoll.org/recoll.conf). You probably do not want
   to edit this by hand.

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

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

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

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

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

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

   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]).

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

   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.

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

     * File path parameters may contain non-ascii characters and
       should use the exact same byte values as found in the file
       system directory. Usually, this means that the configuration
       file should use the system default locale encoding.

     * The unac_except_trans parameter should be encoded in UTF-8. If
       your system locale is not UTF-8, and you need to also specify
       non-ascii file paths, this poses a difficulty because common
       text editors cannot handle multiple encodings in a single
       file. In this relatively unlikely case, you can edit the
       configuration file as two separate text files with appropriate
       encodings, and concatenate them to create the complete
       configuration.

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

  5.4.1. 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.

   Most of the following parameters can be changed from the Index
   Configuration menu in the recoll interface. Some can only be set
   by editing the configuration file.

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

    5.4.1.1. Parameters affecting what documents we index:

   topdirs

           Specifies the list of directories or files to index
           (recursively for directories). You can use symbolic links
           as elements of this list. See the followLinks option about
           following symbolic links found under the top elements (not
           followed by default).

   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 \
                *~ .beagle .git .hg .bzr loop.ps .xsession-errors \
                .recoll* xapiandb recollrc recoll.conf

           The list can be redefined at any sub-directory in the
           indexed area.

           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, email user agents like
           thunderbird usually store messages in hidden directories,
           and you probably want this indexed. One possible solution
           is to have .* in skippedNames, and add things like
           ~/.thunderbird or ~/.evolution in topdirs.

           Not even the file names are indexed for patterns in this
           list. See the recoll_noindex variable in mimemap for an
           alternative approach which indexes the file names.

   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
              

   skippedPathsFnmPathname

           The values in the *skippedPaths variables are matched by
           default with fnmatch(3), with the FNM_PATHNAME and
           FNM_LEADING_DIR flags. This means that '/' characters must
           be matched explicitely. You can set
           skippedPathsFnmPathname to 0 to disable the use of
           FNM_PATHNAME (meaning that /*/dir3 will match
           /dir1/dir2/dir3).

   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.

   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.

   compressedfilemaxkbs

           Size limit for compressed (.gz or .bz2) files. These need
           to be decompressed in a temporary directory for
           identification, which can be very wasteful if
           'uninteresting' big compressed files are present. Negative
           means no limit, 0 means no processing of any compressed
           file. Defaults to -1.

   textfilemaxmbs

           Maximum size for text files. Very big text files are often
           uninteresting logs. Set to -1 to disable (default 20MB).

   textfilepagekbs

           If set to other than -1, text files will be indexed as
           multiple documents of the given page size. This may be
           useful if you do want to index very big text files as it
           will both reduce memory usage at index time and help with
           loading data to the preview window. A size of a few
           megabytes would seem reasonable (default: 1MB).

   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.

   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.

   processbeaglequeue

           If this is set, process the directory where Beagle Web
           browser plugins copy visited pages for indexing. Of
           course, Beagle MUST NOT be running, else things will
           behave strangely.

   beaglequeuedir

           The path to the Beagle indexing queue. This is hard-coded
           in the Beagle plugin as ~/.beagle/ToIndex so there should
           be no need to change it.

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

    5.4.1.2. Parameters affecting how we generate terms:

   Changing some of these parameters will imply a full reindex. Also,
   when using multiple indexes, it may not make sense to search
   indexes that don't share the values for these parameters, because
   they usually affect both search and index operations.

   nonumbers

           If this set to true, no terms will be generated for
           numbers. For example "123", "1.5e6", 192.168.1.4, would
           not be indexed ("value123" would still be). Numbers are
           often quite interesting to search for, and this should
           probably not be set except for special situations, ie,
           scientific documents with huge amounts of numbers in them.
           This can only be set for a whole index, not for a subtree.

   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.

   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.

   unac_except_trans

           This is a list of characters, encoded in UTF-8, which
           should be handled specially when converting text to
           unaccented lowercase. For example, in Swedish, the letter
           a with diaeresis has full alphabet citizenship and should
           not be turned into an a. Each element in the
           space-separated list has the special character as first
           element and the translation following. The handling of
           both the lowercase and upper-case versions of a character
           should be specified, as appartenance to the list will
           turn-off both standard accent and case processing. Example
           for Swedish:

 unac_except_trans =  aaaa AAaa a:a: A:a: o:o: O:o:
            

           Note that the translation is not limited to a single
           character, you could very well have something like u:ue in
           the list.

           This parameter can't be defined for subdirectories, it is
           global, because there is no way to do otherwise when
           querying. If you have document sets which would need
           different values, you will have to index and query them
           separately.

   maildefcharset

           This can be used to define the default character set
           specifically for email messages which don't specify it.
           This is mainly useful for readpst (libpst) dumps, which
           are utf-8 but do not say so.

   localfields

           This allows setting fields for all documents under a given
           directory. Typical usage would be to set an "rclaptg"
           field, to be used in mimeview to select a specific viewer.
           If several fields are to be set, they should be separated
           with a colon (':') character (which there is currently no
           way to escape). Ie: localfields= rclaptg=gnus:other = val,
           then select specifier viewer with mimetype|tag=... in
           mimeview.

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

    5.4.1.3. Parameters affecting where and how we store things:

   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.

   idxstatusfile

           The name of the scratch file where the indexer process
           updates its status. Default: idxstatus.txt inside the
           configuration directory.

   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.

   mboxcachedir

           The directory where mbox message offsets cache files are
           held. This is normally $RECOLL_CONFDIR/mboxcache, but it
           may be useful to share a directory between different
           configurations.

   mboxcacheminmbs

           The minimum mbox file size over which we cache the
           offsets. There is really no sense in caching offsets for
           small files. The default is 5 MB.

   webcachedir

           This is only used by the Beagle web browser plugin
           indexing code, and defines where the cache for visited
           pages will live. Default: $RECOLL_CONFDIR/webcache

   webcachemaxmbs

           This is only used by the Beagle web browser plugin
           indexing code, and defines the maximum size for the web
           page cache. Default: 40 MB.

   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
           (or XAPIAN_FLUSH_THRESHOLD) documents, which gives little
           memory usage control, as memory usage depends on average
           document size. The default value is 10.

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

    5.4.1.4. Miscellaneous parameters:

   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.

   mondelaypatterns

           This allows specify wildcard path patterns (processed with
           fnmatch(3) with 0 flag), to match files which change too
           often and for which a delay should be observed before
           re-indexing. This is a space-separated list, each entry
           being a pattern and a time in seconds, separated by a
           colon. You can use double quotes if a path entry contains
           white space. Example:

 mondelaypatterns = *.log:20 "this one has spaces*:10"
              

   monixinterval

           Minimum interval (seconds) for processing the indexing
           queue. The real time monitor does not process each event
           when it comes in, but will wait this time for the queue to
           accumulate to diminish overhead and in order to aggregate
           multiple events to the same file. Default 30 S.

   monauxinterval

           Period (in seconds) at which the real time monitor will
           regenerate the auxiliary databases (spelling, stemming) if
           needed. The default is one hour.

   filtermaxseconds

           Maximum filter execution time, after which it is aborted.
           Some postscript programs just loop...

   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.

   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.

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

  5.4.2. The fields file

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

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

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

   Field names should be lowercase alphabetic ASCII.

   [prefixes]

           A field becomes indexed (searchable) by having a prefix
           defined in this section.

   [stored]

           A field becomes stored (displayable inside results) by
           having its name listed in this section (typically with an
           empty value).

   [aliases]

           This section defines lists of synonyms for the canonical
           names used inside the [prefixes] and [stored] sections

   filter-specific sections

           Some filters may need specific configuration for handling
           fields. Only the email message filter currently has such a
           section (named [mail]). It allows indexing arbitrary email
           headers in addition to the ones indexed by default. Other
           such sections may appear in the future.

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

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

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

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

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

  5.4.3. 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 a few
   differences: it will not affect directories, it cannot be made
   dependant on the file-system location (it is a configuration-wide
   parameter), and the file names will still be indexed (not even the
   file names are indexed for patterns in skippedNames.
   recoll_noindex 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.

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

  5.4.4. 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).

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

  5.4.5. The mimeview file

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

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

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

   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.

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

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

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

     * %D. Document date

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

     * %F. Original file name. Same as %f except if a temporary file
       is used.

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

     * %M. Mime type

     * %U, %u. Url.

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

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

  5.4.6. Examples of configuration adjustments

    5.4.6.1. 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 Open link in the result list (when found by file name).
   The file names end in .blob and can be displayed by application
   blobviewer.

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

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

 .blob = application/x-blobapp

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

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

 application/x-blobapp = blobviewer %f

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

   If you just wanted to change the application used by 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. mimeview can also be modified from the Gui.

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

    5.4.6.2. 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 or html
   contents on the standard output.

   The filter programming section describes in more detail how to
   write a filter.

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