Copyright © 2005 Jean-Francois Dockes
If you do not like reading manuals (who does?) and would like to give Recoll a try, just perform installation and start the recoll user interface, which will index your home directory and let you search it right after.
Do not do this if your home has a huge number of documents and you do not want to wait or are very short on disk space. In this case, you may want to edit the configuration file first to restrict the indexed area.
Also be aware that you will need to install the appropriate supporting applications for document types that need them (for example antiword for ms-word files), and that the default character set used to read raw text files for indexing is iso8859-1, which may not be appropriate for you.
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.
This mode of operation has been made very familiar by www search engines.
The notion of relevance is a difficult one, as only you, the user, actually know which documents are relevant to your search, and the application can only try a guess. The quality of this guess is probably the most important element for a search application.
In many cases, you are looking for all the forms of a word, not for a specific form or spelling. These different forms may include plurals, different tenses for a verb, or terms derived from the same root or stem (exemple: floor, floors, floored, floorings...). Recoll will by default expand queries to all such related terms (words that reduce to the same stem). This expansion can be disabled at search time.
Stemming, by itself, does not provide for misspellings or phonetic searches. Recoll currently does not support these.
Recoll uses the Xapian information retrieval library as its storage and retrieval engine. Xapian is a very mature package using a sophisticated probabilistic ranking model. Recoll provides the interface to get data into (indexation) and out (searching) of the system.
In practice, Xapian works by remembering where terms appear in your document files. The acquisition process is called indexation.
The resulting database 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.
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 database. It has input filters for many document types.
Stemming depends on the document language. Recoll stores the unstemmed versions of terms and uses auxiliary databases for term expansion. It can switch stemming languages, or add a language, without reindexing. Storing documents in different languages in the same database is possible, and useful in practice, but does introduce possibilities of confusion. Recoll makes no attempt at automatic language recognition.
Recoll has many parameters which define exactly what to index, and how to classify and decode the source documents. These are kept in a configuration file. A sample configuration is installed into the .recoll subdirectory of your home directory when you first execute a Recoll command. The initial 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.
Indexation is started automatically the first time you execute the recoll search graphical user interface, or by executing the recollindex command.
Searches are performed inside the recoll program, which has many options to help you find what you are looking for.
Indexation is the process by which the set of documents is analyzed and the data entered into the database. Recoll indexation is normally incremental: documents will only be processed if they have been modified. On the first execution, of course, all documents will need processing. A full index build can be forced later on by specifying an option to the indexation command (recollindex -z).
Recoll indexation takes place at discrete times. There is currently no interface to real time file modification monitors. The typical usage is to have a nightly indexation run programmed into your cron file.
Recoll knows about quite a few different document types. The parameters for document types recognition and processing are set in configuration files Most file types, like HTML or word processing files, only hold one document. Some file types, like mail folder files can hold many individually indexed documents.
Recoll indexation processes plain text, HTML, openoffice and e-mail files internally. Other types (ie: postscript, pdf, ms-word, rtf) need external applications for preprocessing. The list is in the installation section.
Without further configuration, Recoll will index all appropriate files from your home directory, with a reasonable set of defaults, if you live in western Europe or the USA. If your normal character set is not iso8859-1, you almost certainly need to adjust the configuration.
The main configuration file is named $HOME/.recoll/recoll.conf by default or $RECOLL_CONFDIR/recoll.conf if RECOLL_CONFDIR is set.
The most accurate documentation for editing the file is given by comments inside the default file that will be created when you first start recoll. If you want to adjust the configuration before indexation, just click Cancel when the program asks if it should start initial indexation.
The configuration is also documented inside the installation chapter of this document, or in the recoll.conf(5) man page.
Indexation is performed either by the recollindex program, or by the indexation thread inside the recoll program (use the File menu).
If the recoll program finds no database when it starts, it will automatically start indexation (except if cancelled).
It is best to avoid interrupting the indexation process, as this may sometimes leave the database in a bad state. This is not a serious problem, as you then just need to clear everything and restart the indexation: the database files are normally stored in the $HOME/.recoll/xapiandb directory, which you can just delete if needed. Alternatively, you can start recollindex -z, which will reset the database before indexation.
The most common way to set up indexation is to have a cron task execute it every night. For example the following crontab entry would do it every day at 3:30AM (supposing recollindex is in your PATH):
30 3 * * * recollindex > /tmp/recolltrace 2>&1
The usual command to edit your crontab is crontab -e (which will usually start the vi editor to edit the file). You may have more sophisticated tools available on your system.
The recoll program provides the user interface for searching. It is based on the QT library.
Start the recoll program, then enter search term(s) in the text field at the top left of the window. Clicking the Search button or hitting the Enter key will start a search. By default, this will look for documents with any of the terms (the ones with more terms will get better scores). You can check the All terms checkbox to ensure that only documents with all the terms will be returned. Use the Tools / Advanced search dialog for more complex searches.
After starting a search, a list of results will instantly be displayed in the main list window. Clicking on an entry will open an internal preview window for the document. Double-clicking will attempt to start an external viewer (have a look at the ~/.recoll/mimeconf file to see how these are configured).
By default, the document list is presented in order of relevance (how well the system estimates that the document matches the query). You can specify a different ordering by using the Tools / Sort parameters dialog.
The advanced search dialog has fields that will allow a more refined search, looking for documents with all given words, a given exact phrase, or none of the given words (all fields may be combined by an implicit AND clause).
It will let you search for documents of specific mime types (ie: only text/plain, or text/html or application/pdf etc...)
It will let you restrict the search results to a subtree of the indexed area.
Click on the Start Search button in the advanced search dialog to start the search. The button in the main window always performs a simple search.
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.
The documents in a result list are normally sorted in order of relevance. It is possible to specify different sort parameters by using the Sort parameters dialog (located in the Tools menu).
The tool sorts a specified number of the most relevant documents in the result list, according to specified criteria. The currently available criteria are date and mime type.
The sort parameters stay in effect until they are explicitely reset, or the program exits.
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.
Phrases. A phrase can be looked for by enclosing it in double quotes. Example: "user manual" will look only for occurrences of user immediately followed by manual. You can use the This exact phrase field of the advanced search dialog to the same effect.
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.
Quitting. Entering ^Q almost anywhere will close the application.
Closing previews. Entering ^W in a preview tab will close it (and, for the last tab, close the preview window).
It is possible to customise some aspects of the search interface by using Query configuration entry in the Preferences menu.
There are two tabs in the dialog, to modify the appearance of the user interface (result list appearance), or the parameters used for searching (language used for stem expansion).
The stemming language can be chosen among those that were specified in the configuration file, or later added with recollindex -s (See the recollindex manual). Stemming languages which are dynamically added will be deleted at the next indexation pass unless they are also added in the configuration file.
At the very least, you will need to download and install the xapian core package (Recoll currently uses version 0.9.2), and the qt runtime and development packages (Recoll currently uses version 3.3.3).
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.
External file types. Recoll uses external applications to index some file types. You need to install them for the file types that you wish to have indexed:
Recoll has been built on Linux (redhat7.3, mandriva 2005), FreeBSD and Solaris 8. If you build on another system, I would very much welcome patches.
Normal procedure:
cd recoll-xxx
configure
make
(practises usual hardship-repelling invocations)
There little autoconfiguration. The configure script will mainly link one of the system-specific files in the mk directory to mk/sysconf. If your system is not known yet, it will tell you as much, and you may want to manually copy and modify one of the existing files (the new file name should be the output of uname -s).
Either type make install or execute recollinstall targetdir, in the root of the source tree. This will copy the commands to $targetdir/bin and the sample configuration files, scripts and other shared data to $targetdir/share/recoll.
If you are lucky enough to be using a port system or a prebuilt package (RPM or other), just follow the usual procedure, and have a look at the configuration section.
The unpackaged binary versions are just compressed tar files of a build tree, where only the useful parts were kept (executables and sample configuration).
The executable binary files are built with a static link to libxapian and libiconv, to make installation easier (no dependencies). However, this also means that you cannot change the versions which are used.
After extracting the tar file, you can proceed with installation as if you had built the package from source.
The personal configuration files and the database are normally kept in the .recoll directory in your home (this can be changed with the RECOLL_CONFDIR environment variable, and a parameter inside the main configuration file). If this directory does not exist when recoll or recollindex are started, the directory will be created and the sample configuration files will be copied. recoll will give you a chance to edit the configuration file before starting indexation. recollindex will proceed immediately.
Most of the parameters specific to the recoll GUI are set through the Preferences menu and stored in the standard QT place ($HOME/.qt/recollrc). You probably do not want to edit this by hand.
For other options, Recoll uses text configuration files. You will have to edit them by hand for now (there is still some hope for a GUI configuration tool in the future). The most accurate documentation for the configuration parameters is given by comments inside the sample files, and we will just give a general overview here.
All configuration files share the same format. For exemple, a short extract of the main configuration file might look as follows:
# Space-separated list of directories to index.
topdirs = ~/docs /usr/share/doc
[~/somedirectory-with-utf8-txt-files]
defaultcharset = utf-8
There are three kinds of lines:
Comment (starts with #) or empty.
Parameter affectation (name = value).
Section definition ([somedirname]).
Section lines allow redefining some parameters for a directory subtree. Some of the parameters used for indexation are looked up hierarchically from the more to the less specific. Not all parameters can be meaningfully redefined, this is specified for each in the next section.
The tilde character (~) is expanded in file names to the name of the user's home directory.
White space is used for separation inside lists. Elements with embedded spaces can be quoted using double-quotes.
~/.recoll/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, use recoll to copy the sample configuration, click Cancel, and edit the configuration file before restarting the command. This will start the initial indexation, which may take some time.
Paramers:
Specifies the list of directories to index (recursively).
A space-separated list of patterns for names of files or directories that should be completely ignored. The list defined in the default file is:
*~ #* bin CVS Cache caughtspam tmpThe list can be redefined for subdirectories, but is only actually changed for the top level ones in topdirs
Verbosity level for recoll and recollindex. A value of 4 lists quite a lot of debug/information messages. 3 only lists errors.
Where should the messages go. 'stderr' can be used as a special value.
A directory to search for the external filter scripts used to index some types of files. The value should not be changed, except if you want to modify one of the default scripts. The value can be redefined for any subdirectory.
A list of languages for which the stem expansion databases will be built. See recollindex(1) for possible values. You can add a stem expansion database for a different language by using recollindex -s, but it will be deleted during the next indexation. Only languages listed in the configuration file are permanent.
The name of the directory where recoll result list icons are stored. You can change this if you want different images.
The name of the Xapian database directory. It will be created if needed when the database is initialized.
The name of the character set used for files that do not contain a character set definition (ie: plain text files). This can be redefined for any subdirectory.
Decide if we try to guess the character set of files if no internal value is available (ie: for plain text files). This does not work well in general, and should probably not be used.
Decide if we use the file -i system command as a final step for determining the mime type for a file (the main procedure uses suffix associations as defined in the mimemap file). This can be useful for files with suffixless names, but it will also cause the indexation of many bogus "text" files.
~/.recoll/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).
mimemap also has a list of extensions which should be ignored totally (to avoid losing time by executing file for things that certainly should not be indexed).
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.
~/.recoll/mimeconf specifies how the different mime types are handled for indexation, and for display.
Changing the indexation parameters is probably not a good idea except if you are a Recoll developper.
You may want to adjust the external viewers defined in (ie: html is either previewed internally or displayed using firefox, but you may prefer mozilla...). Look for the [view] section.
You can also change the icons which are displayed by recoll in the result lists (the values are the basenames of the png images inside the iconsdir directory (specified in recoll.conf).