git clone https://@opensourceprojects.eu/git/p/recoll1/code recoll1-code
Read Me
More documentation can be found in the doc/ directory or at http://www.recoll.org
Recoll user manual
Jean-Francois Dockes
<jean-francois.dockes@wanadoo.fr>
Copyright (c) 2005 Jean-Francois Dockes
This document introduces full text search notions and describes the
installation and use of the Recoll application. It currently describes
Recoll 1.9.
[ Split HTML / Single HTML ]
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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. Index formats
2.2.2. Security aspects
2.3. The indexing configuration
2.4. Periodic indexing
2.4.1. Starting indexing
2.4.2. Using cron to automate indexing
2.5. Real time indexing
3. Searching
3.1. Simple search
3.2. The result list
3.2.1. The result list right-click menu
3.3. The preview window
3.4. The query language
3.5. Complex/advanced search
3.6. The term explorer tool
3.7. More about wildcards
3.8. Multiple databases
3.9. Document history
3.10. Sorting search results
3.11. Search tips, shortcuts
3.12. Customizing the search interface
4. Installation
4.1. Installing a prebuilt copy
4.1.1. Installing through a package system
4.1.2. Installing a prebuilt Recoll
4.2. Supporting packages
4.3. Building from source
4.3.1. Prerequisites
4.3.2. Building
4.3.3. Installation
4.4. Configuration overview
4.4.1. Main configuration file
4.4.2. The mimemap file
4.4.3. The mimeconf file
4.4.4. The mimeview file
4.4.5. Examples of configuration adjustments
4.5. Extending Recoll
4.5.1. Writing a document filter
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Chapter 1. Introduction
1.1. Giving it a try
If you do not like reading manuals (who does?) and would like to give
Recoll a try, just perform installation and start the recoll user
interface, which will index your home directory by default, allowing you
to search immediately after indexing completes.
Do not do this if your home directory contains a huge number of documents
and you do not want to wait or are very short on disk space. In this case,
you may want to edit the configuration file first to restrict the indexed
area.
Also be aware that you may need to install the appropriate supporting
applications for document types that need them (for example antiword for
ms-word files).
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1.2. Full text search
Recoll is a full text search application. Full text search applications
let you find your data by content rather than by external attributes (like
a file name). More specifically, they will let you specify words (terms)
that should or should not appear in the text you are looking for, and
return a list of matching documents, ordered so that the most relevant
documents will appear first.
You do not need to remember in what file or email message you stored a
given piece of information. You just ask for related terms, and the tool
will return a list of documents where those terms are prominent, in a
similar way to Internet search engines.
Recoll tries to determine which documents are most relevant to the search
terms you provide. Computer algorithms for determining relevance can be
very complex, and in general are inferior to the power of the human mind
to rapidly determine relevance. The quality of relevance guessing by the
search tool is probably the most important element for a search
application.
In many cases, you are looking for all the forms of a word, not for a
specific form or spelling. These different forms may include plurals,
different tenses for a verb, or terms derived from the same root or stem
(example: floor, floors, floored, flooring...). Recoll will by default
expand queries to all such related terms (words that reduce to the same
stem). This expansion can be disabled at search time.
Stemming, by itself, does not accommodate for misspellings or phonetic
searches. Recoll supports these features through a specific tool (the term
explorer) which will let you explore the set of index terms along
different modes.
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1.3. Recoll overview
Recoll uses the Xapian information retrieval library as its storage and
retrieval engine. Xapian is a very mature package using a sophisticated
probabilistic ranking model. Recoll provides the interface to get data
into (indexing) and out (searching) of the system.
In practice, Xapian works by remembering where terms appear in your
document files. The acquisition process is called indexing.
The resulting index can be big (roughly the size of the original document
set), but it is not a document archive. Recoll can only display documents
that still exist at the place from which they were indexed. (Actually,
there is a way to reconstruct a document from the information in the
index, but the result is not nice, as all formatting, punctuation and
capitalization are lost).
Recoll stores all internal data in Unicode UTF-8 format, and it can index
files with different character sets, encodings, and languages into the
same index. It has input filters for many document types.
Stemming depends on the document language. Recoll stores the unstemmed
versions of terms and uses auxiliary databases for term expansion. It can
switch stemming languages, or add a language, without re-indexing. Storing
documents in different languages in the same index is possible, and useful
in practice, but does introduce possibilities of confusion. Recoll
currently makes no attempt at automatic language recognition.
Recoll has many parameters which define exactly what to index, and how to
classify and decode the source documents. These are kept in a
configuration file. A default configuration is copied into a standard
location (usually something like /usr/[local/]share/recoll/examples)
during installation. The default parameters from this file may be
overridden by values that you set inside your personal configuration,
found by default in the .recoll sub-directory of your home directory. The
default configuration will index your home directory with default
parameters and should be sufficient for giving Recoll a try, but you may
want to adjust it later.
Indexing is started automatically the first time you execute the recoll
search graphical user interface, or by executing the recollindex command.
Searches are performed inside the recoll program, which has many options
to help you find what you are looking for.
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Chapter 2. Indexing
2.1. Introduction
Indexing is the process by which the set of documents is analyzed and the
data entered into the database. Recoll indexing is normally incremental:
documents will only be processed if they have been modified. On the first
execution, of course, all documents will need processing. A full index
build can be forced later by specifying an option to the indexing command
(recollindex -z).
Recoll indexing can be performed with two different methods:
* Periodic indexing: indexing takes place at discrete times, by
executing the recollindex command. The typical usage is to have a
nightly indexing run programmed into your cron file.
* Real time indexing: indexing takes place as soon as a file is created
or changed. recollindex runs as a daemon and uses a file system
alteration monitor such as Fam, Gamin or inotify do detect file
changes. Monitoring a big directory tree can consume significant
system resources.
The choice between the two methods is mostly a matter of preference, and
they can be combined by setting up multiple indexes (ie: use periodic
indexing on a big documentation directory, and real time indexing on a
small home directory). Monitoring a big file system tree can consume
significant system resources, for dubious gains.
Recoll knows about quite a few different document types. The parameters
for document types recognition and processing are set in configuration
files Most file types, like HTML or word processing files, only hold one
document. Some file types, like mail folder files can hold many
individually indexed documents.
Recoll indexing processes plain text, HTML, openoffice and e-mail files
internally. Other types (ie: postscript, pdf, ms-word, rtf) need external
applications for preprocessing. The list is in the installation section.
Without further configuration, Recoll will index all appropriate files
from your home directory, with a reasonable set of defaults.
In some cases, it may be interesting to index different areas of the file
system to separate databases. You can do this by using multiple
configuration directories, each indexing a file system area to a specific
database. See the section about using multiple databases for more
information on multiple configurations and indexes.
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2.2. Index storage
The default location for the index data is the xapiandb subdirectory of
the Recoll configuration directory, typically $HOME/.recoll/xapiandb/.
This can be changed via two different methods (with different purposes):
* You can specify a different configuration directory by setting the
RECOLL_CONFDIR environment variable, or using the -c option to the
Recoll commands. This method would typically be used to index
different areas of the file system to different indexes. For example,
if you were to issue the following commands:
export RECOLL_CONFDIR=~/.indexes-email
recoll
Then Recoll would use configuration files stored in ~/.indexes-email/
and, (unless specified otherwise in recoll.conf) would look for the
index in ~/.indexes-email/xapiandb/.
Using multiple configuration directories and configuration options
allows you to tailor multiple configurations and indexes to handle
whatever subset of the available data that you wish to make
searchable.
* You can also specify a different storage location for the index by
setting the dbdir parameter in the configuration file (see the
configuration section). This method would mainly be of use if you
wanted to keep the configuration directory in its default location,
but desired another location for the index, typically out of disk
occupation concerns.
The size of the index is determined by the size of the set of documents,
but the ratio can vary a lot. For a typical mixed set of documents, the
index size will often be close to the data set size. In specific cases (a
set of compressed mbox files for example), the index can become much
bigger than the documents. It may also be much smaller if the documents
contain a lot of images or other non-indexed data (an extreme example
being a set of mp3 files where only the tags would be indexed).
Of course, images, sound and video do not increase the index size, which
means that it will be quite typical nowadays (2006), that even a big index
will be negligible against the total amount of data on the computer.
The index data directory (xapiandb) only contains data that can be
completely rebuilt by an index run, and it can always be destroyed safely.
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2.2.1. Index formats
Xapian has had two possible index formats for quite some time. The "old"
one named Quartz, and the new one named Flint. Xapian 0.9 used Quartz by
default, but could use Flint if a specific environment variable
(XAPIAN_PREFER_FLINT) was set. Xapian 1.0 still supports Quartz but will
use Flint by default for new index creations.
The number of disk accesses performed during indexing has been much
optimized in the new Flint engine and you may see indexing times improved
by 50% in some cases (compared to Quartz), typically for big indexes where
disk accesses dominate the indexing time. There is also a more modest
improvement of index size.
Xapian will not convert automatically an existing index from the Quartz to
the Flint format. If you have an older index and want to take advantage of
the new format (which can be done without setting the environment variable
as of Recoll 1.8.2 and Xapian 1.0.0), you will have to explicitely delete
the old index, then run a normal indexing process.
Unfortunately, using the -z option to recollindex is not sufficient to
change the format, you have to delete all files inside the index directory
(typically ~/.recoll/xapiandb) before starting indexing.
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2.2.2. Security aspects
The Recoll index does not hold copies of the indexed documents. But it
does hold enough data to allow for an almost complete reconstruction. If
confidential data is indexed, access to the database directory should be
restricted.
As of version 1.4, Recoll will create the configuration directory with a
mode of 0700 (access by owner only). As the index data directory is by
default a sub-directory of the configuration directory, this should result
in appropriate protection.
If you use another setup, you should think of the kind of protection you
need for your index, and set the directory and files access modes
appropriately.
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2.3. The indexing configuration
You can control which areas of the file system are indexed, and how files
are processed, by setting variables inside the Recoll configuration files.
You can also use multiple indexes defined by separate configurations,
typically to separate personal and shared indexes, or to take advantage of
the organization of your data to improve search precision.
The first time you start recoll, you will be asked whether or not you
would like recoll to build the index. If you want to adjust the
configuration before indexing, just click Cancel at this point. That way,
recoll will have created a ~/.recoll directory containing empty
configuration files.
The configuration is documented inside the installation chapter of this
document, or in the recoll.conf(5) man page, but the most current
information will most likely be the comments inside the sample file. The
most immediately useful variable you may interested in is probably
topdirs, which determines what subtrees get indexed.
The applications needed to index file types other than text, HTML or email
(ie: pdf, postscript, ms-word...) are described in the external packages
section
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2.4. Periodic indexing
2.4.1. Starting indexing
Indexing is performed either by the recollindex program, or by the
indexing thread inside the recoll program (use the File menu). Both
programs will use of the RECOLL_CONFDIR variable or accept a -c confdir
option to specify the configuration directory to be used.
If the recoll program finds no index when it starts, it will automatically
start indexing (except if canceled).
It is best to avoid interrupting the indexing process, as this may
sometimes leave the index in a bad state. This is not a serious problem,
as you then just need to delete the index files and restart the indexing.
The index files are normally stored in the $HOME/.recoll/xapiandb
directory, which you can just delete if needed. Alternatively, you can
start recollindex with option -z, which will reset the database before
indexing.
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2.4.2. Using cron to automate indexing
The most common way to set up indexing is to have a cron task execute it
every night. For example the following crontab entry would do it every day
at 3:30AM (supposing recollindex is in your PATH):
30 3 * * * recollindex > /tmp/recolltrace 2>&1
The usual command to edit your crontab is crontab -e (which will usually
start the vi editor to edit the file). You may have more sophisticated
tools available on your system.
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2.5. Real time indexing
Real time monitoring/indexing is performed by starting the recollindex -m
command. With this option, recollindex will detach from the terminal and
become a daemon, permanently monitoring file changes and updating the
index.
The real time indexing support can be customised during package
configuration with the --with[out]-fam or --with[out]-inotify options. The
default is currently to include inotify monitoring on systems that support
it.
The rclmon.sh script can be used to easily start and stop the daemon. It
can be found in the examples directory (typically
/usr/local/[share/]recoll/examples).
Starting the daemon is normally performed as part of the user session
script. For example, my out of fashion xdm-based session has a .xsession
script with the following lines at the end:
recollconf=$HOME/.recoll-home
recolldata=/usr/local/share/recoll
RECOLL_CONFDIR=$recollconf $recolldata/examples/rclmon.sh start
fvwm
The indexing daemon gets started, then the window manager, for which the
session waits.
By default the indexing daemon will monitor the state of the X11 session,
and exit when it finishes, it is not necessary to kill it explicitely.
(The X11 server monitoring can be disabled with option -x to recollindex).
Under KDE, you can place a small script to start recollindex -m under
$HOME/.kde/Autostart. This will be executed when the session begins.
There is a similar mechanism under Gnome (find the session control tool in
the menus and use the "Startup programs" tab).
By default, the indexing daemon will write its messages to a file inside
the configuration directory (this is controlled by the daemlogfilename and
daemloglevel configuration parameters). You may want to change this. Also
the log file will only be truncated when the daemon starts. If the daemon
runs permanently, the log file may grow quite big, depending on the log
level.
While it is convenient that data is indexed in real time, repeated
indexing can generate a significant load on the system when files such as
email folders change. You probably do not want to enable it if your system
is short on resources. Periodic indexing is adequate in most cases.
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Chapter 3. Searching
The recoll program provides the user interface for searching. It is based
on the QT library.
recoll has two search modes:
* Simple search (the default, on the main screen) has a single entry
field where you can enter multiple words.
* Advanced search (a panel accessed through the Tools menu or the
toolbox bar icon) shas multiple entry fields, which you may use to
build a logical condition, with additional filtering on file type and
location in the file system.
In most cases, you can enter the terms as you think them, even if they
contain embedded punctuation or other non-textual characters. For exemple,
Recoll can handle things like e-mail addresses, or arbitrary cut and paste
from another text window, punctation and all.
The main case where you should enter text differently from how it is
printed is for east-oriental languages written with Chinese characters.
Words composed of single or multiple characters should be entered
separated by white space in this case (they would typically be printed
without white space).
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3.1. Simple search
1. Start the recoll program.
2. Possibly choose a search mode: Any term or All terms or File name.
3. Enter search term(s) in the text field at the top of the window.
4. Click the Search button or hit the Enter key to start the search.
The initial default search mode is All terms. This will look for documents
containing all of the search terms (the ones with more terms will get
better scores). Any term will search for documents where at least one of
the terms appear. File name will specifically look for file names.
The fourth entry (Query Language) is described in its own section.
All search modes allow wildcards inside terms (*, ?, []). You may want to
have a look at the section about wildcards for more information about
this.
You can search for exact phrases (adjacent words in a given order) by
enclosing the input inside double quotes. Ex: "virtual reality".
Character case has no influence on search, except that you can disable
stem expansion for any term by capitalizing it. Ie: a search for floor
will also normally look for flooring, floored, etc., but a search for
Floor will only look for floor, in any character case (stemming can also
be disabled globally in the preferences).
Recoll remembers the last few searches that you performed. You can use the
simple search text entry widget (a combobox) to recall them (click on the
thing at the right of the text field). Please note, however, that only the
search texts are remembered, not the mode (all/any/file name).
Typing Esc Space while entering a word in the simple search entry will
open a window with possible completions for the word. The completions are
extracted from the database.
Double-clicking on a word in the result list or a preview window will
insert it into the simple search entry field.
Note that, apart from wildcard characters (single ? characters are ok),
you can cut and paste any text into an All terms or Any term search field,
punctuation, newlines and all. Recoll will process it and produce a
meaningful search. This is what most differentiates this mode from the
Query Language mode, where you have to care about the syntax.
You can use the Tools / Advanced search dialog for more complex searches.
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3.2. The result list
After starting a search, a list of results will instantly be displayed in
the main list window.
By default, the document list is presented in order of relevance (how well
the system estimates that the document matches the query). You can specify
a different ordering by using the Tools / Sort parameters dialog.
Clicking on the Preview link for an entry will open an internal preview
window for the document. Further Preview clicks for the same search will
open tabs in the existing preview window. You can use Shift+Click to force
the creation of another preview window, which may be useful to view the
documents side by side. (You can also browse successive results in a
single preview window by typing Shift+ArrowUp/Down in the window).
Clicking the Edit link will attempt to start an external viewer. The
viewers can be configured through the user preferences dialog, or by
editing the mimeview configuration file.
The Preview and Edit edit links may not be present for all entries,
meaning that Recoll has no configured way to preview a given file type
(which was indexed by name only), or no configured external viewer for the
file type. This can sometimes be adjusted simply by tweaking the mimemap
and mimeview configuration files (the latter can be modified with the user
preferences dialog).
You can click on the Query details link at the top of the results page to
see the query actually performed, after stem expansion and other
processing.
Double-clicking on any word inside the result list or a preview window
will insert it into the simple search text.
The result list is divided into pages (the size of which you can change in
the preferences). Use the arrow buttons in the toolbar or the links at the
bottom of the page to browse the results.
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3.2.1. The result list right-click menu
Apart from the preview and edit links, you can display a pop-up menu by
right-clicking over a paragraph in the result list. This menu has the
following entries:
* Preview
* Edit
* Copy File Name
* Copy Url
* Find similar
* Find similar
* Parent document
The Preview and Edit entries do the same thing as the corresponding links.
The Copy File Name and Copy Url copy the relevant data to the clipboard,
for later pasting.
The Find similar entry will select a number of relevant term from the
current document and enter them into the simple search field. You can then
start a simple search, with a good chance of finding documents related to
the current result.
The Parent document entry will appear for documents which are not actually
files but are part of, or attached to, a higher level document. This entry
is mainly useful for email attachments and permits viewing the message to
which the document is attached. Note that the entry will also appear for
an email which is part of an mbox folder file, but that you can't actually
visualize the folder (there will be an error dialog if you try). Recoll is
unfortunately not yet smart enough to disable the entry in this case.
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3.3. The preview window
The preview window opens when you first click a Preview link inside the
result list.
Subsequent preview requests for a given search open new tabs in the
existing window (except if you hold the Shift key while clicking which
will open a new window for side by side viewing).
Starting another search and requesting a preview will create a new preview
window. The old one stays open until you close it.
You can close a preview tab by typing ^W (Ctrl + W) in the window. Closing
the last tab for a window will also close the window.
Of course you can also close a preview window by using the window manager
button in the top of the frame.
You can display successive or previous documents from the result list
inside a preview tab by typing Shift+Down or Shift+Up (Down and Up are the
arrow keys).
The preview tabs have an internal incremental search function. You
initiate the search either by typing a / (slash) inside the text area or
by clicking into the Search for: text field and entering the search
string. You can then use the Next and Previous buttons to find the
next/previous occurrence. You can also type F3 inside the text area to get
to the next occurrence.
If you have a search string entered and you use ^Up/^Down to browse the
results, the search is initiated for each successive document. If the
string is found, the cursor will be positioned at the first occurrence of
the search string.
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3.4. The query language
The query language processor is activated on the simple search entry when
the search mode selector is set to Query Language.
Here follows a sample request that we are going to explain:
author:"john doe" Beatles OR Lennon Live OR Unplugged -potatoes
This would search for all documents with John Doe appearing as a phrase in
the author field (exactly what this is would depend on the document type,
ie: the From: header, for an email message), and containing either beatles
or lennon and either live or unplugged but not potatoes (in any part of
the document).
All elements in the search entry are normally combined with an implicit
AND. It is possible to specify that elements be OR'ed instead, as in
Beatles OR Lennon. The OR must be entered literally (capitals), and it has
priority over the AND associations: word1 word2 OR word3 means word1 AND
(word2 OR word3) not (word1 AND word2) OR word3. Do not enter explicit
parenthesis, they are not supported for now.
An entry preceded by a - specifies a term that should not appear.
The first element in the above exemple, author:"john doe" is a phrase
search limited to a specific field. Phrase searches are specified as usual
by enclosing the words in double quotes. The field specification appears
before the colon (of course this is not limited to phrases, author:Balzac
would be ok too). Recoll currently manages the following fields:
* title, subject or caption are synonyms which specify data to be
searched for in the document title or subject.
* author or from for searching the documents originators.
* keyword for searching the document specified keywords (few documents
actually have any).
As of release 1.9, the filters have the possibility to create other fields
with arbitrary names. No standard filters use this possibility yet.
There are two other elements which may be specified through the field
syntax, but are somewhat special:
* ext for specifying the file name extension (Ex: ext:html)
* mime for specifying the mime type. This one is quite special because
you can specify several values which will be OR'ed (the normal default
for the language is AND). Ex: mime:text/plain mime:text/html.
Specifying an explicit boolean operator or negation (-) before a mime
specification is not supported and will produce strange results.
The query language is currently the only way to use the Recoll field
search capability.
Words inside phrases and capitalized words are not stem-expanded.
Wildcards may be used anywhere inside a term. Specifying a wild-card on
the left of a term can produce a very slow search.
You can use the show query link at the top of the result list to check the
exact query which was finally executed by Xapian.
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3.5. Complex/advanced search
The advanced search dialog has a number of fields that will allow a more
refined search. Each entry field is configurable for the following modes:
* All terms.
* Any term.
* None of the terms.
* Phrase (exact terms in order within an adjustable window).
* Proximity (terms in any order within an adjustable window).
* Filename search with wildcards.
Additional entry fields can be created by clicking the Add clause button.
You can choose that all relevant fields will be combined by either an AND
or an OR conjunction. All types of clauses except "phrase" and "near" can
accept a mix of single words and phrases enclosed in double quotes.
Stemming expansion will be performed for all terms not beginning with a
capital letter, except for terms inside "phrase" clauses. Wildcards will
be processed everywhere.
Advanced search will also let you search for documents of specific mime
types (ie: only text/plain, or text/HTML or application/pdf etc...). The
state of the file type selection can be saved as the default (the file
type filter will not be activated at program start-up, but the lists will
be in the restored state).
You can also restrict the search results to a sub-tree of the indexed
area. If you need to do this often, you may think of setting up multiple
indexes instead, as the performance will be much better.
Click on the Start Search button in the advanced search dialog, or type
Enter in any text field to start the search. The button in the main window
always performs a simple search.
Click on the Show query details link at the top of the result page to see
the query expansion.
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3.6. The term explorer tool
Recoll automatically manages the expansion of search terms to their
derivatives (ie: plural/singular, verb inflections). But there are other
cases where the exact search term is not known. For example, you may not
remember the exact spelling, or only know the beginning of the name.
The term explorer tool (started from the toolbar icon or from the Term
explorer entry of the Tools menu) can be used to search the full index
terms list. It has three modes of operations:
Wildcard
In this mode of operation, you can enter a search string with
shell-like wildcards (*, ?, []). ie: xapi* would display all index
terms beginning with xapi. (More about wildcards here).
Regular expression
This mode will accept a regular expression as input. Example:
word[0-9]+. The expression is implicitely anchored at the
beginning. Ie: press will match pression but not expression. You
can use .*press to match the latter, but be aware that this will
cause a full index term list scan, which can be quite long.
Stem expansion
This mode will perform the usual stem expansion normally done as
part user input processing. As such it is probably mostly useful
to demonstrate the process.
Spelling/Phonetic
In this mode, you enter the term as you think it is spelled, and
Recoll will do its best to find index terms that sound like your
entry. This mode uses the Aspell spelling application, which must
be installed on your system for things to work (if your documents
contain non-ascii characters, Recoll needs an aspell version newer
than 0.60 for UTF-8 support). The language which is used to build
the dictionary out of the index terms (which is done at the end of
an indexing pass) is the one defined by your NLS environment.
Weird things will probably happen if languages are mixed up.
Note that in cases where Recoll does not know the beginning of the string
to search for (ie a wildcard expression like *coll), the expansion can
take quite a long time because the full index term list will have to be
processed. The expansion is currently limited at 200 results for wildcards
and regular expressions.
Double-clicking on a term in the result list will insert it into the
simple search entry field. You can also cut/paste between the result list
and any entry field (the end of lines will be taken care of).
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3.7. More about wildcards
All words entered in Recoll search fields will be processed for wildcard
expansion before the request is finally executed.
The wildcard characters are:
* * which matches 0 or more characters.
* ? which matches a single character.
* [] which allow defining sets of characters to be matched (ex: [abc]
matches a single character which may be 'a' or 'b' or 'c', [0-9]
matches any number.
You should be aware of a few things before using wildcards.
* Using a wildcard character at the beginning of a word can make for a
slow search because Recoll will have to scan the whole index term list
to find the matches.
* Using a * at the end of a word can produce more matches than you would
think, and strange search results. You can use the term explorer tool
to check what completions exist for a given term. You can also see
exactly what search was performed by clicking on the link at the top
of the result list. In general, for natural language terms, stem
expansion will produce better results than an ending * (stem expansion
is turned off when any wildcard character appears in the term).
----------------------------------------------------------------------
3.8. Multiple databases
Multiple Recoll databases or indexes can be created by using several
configuration directories which are usually set to index different areas
of the file system. A specific index can be selected for updating or
searching, using the RECOLL_CONFDIR environment variable or the -c option
to recoll and recollindex.
A recollindex program instance can only update one specific index.
A recoll program instance is also associated with a specific index, which
is the one to be updated by its indexing thread, but it can use any number
of Recoll indexes for searching. The external indexes can be selected
through the external indexes tab in the preferences dialog.
Index selection is performed in two phases. A set of all usable indexes
must first be defined, and then the subset of indexes to be used for
searching. Of course, these parameters are retained across program
executions (there are kept separately for each Recoll configuration). The
set of all indexes is usually quite stable, while the active ones might
typically be adjusted quite frequently.
The main index (defined by RECOLL_CONFDIR) is always active. If this is
undesirable, you can set up your base configuration to index an empty
directory.
As building the set of all indexes can be a little tedious when done
through the user interface, you can use the RECOLL_EXTRA_DBS environment
variable to provide an initial set. This might typically be set up by a
system administrator so that every user does not have to do it. The
variable should define a colon-separated list of index directories, ie:
export RECOLL_EXTRA_DBS=/some/place/xapiandb:/some/other/db
A typical usage scenario for the multiple index feature would be for a
system administrator to set up a central index for shared data, that you
choose to search or not in addition to your personal data. Of course,
there are other possibilities. There are many cases where you know the
subset of files that should be searched, and where narrowing the search
can improve the results. You can achieve approximately the same effect
with the directory filter in advanced search, but multiple indexes will
have much better performance and may be worth the trouble.
----------------------------------------------------------------------
3.9. Document history
Documents that you actually view (with the internal preview or an external
tool) are entered into the document history, which is remembered.
You can display the history list by using the Tools/Doc History menu
entry.
You can erase the document history by using the Erase document history
entry in the File menu.
----------------------------------------------------------------------
3.10. Sorting search results
The documents in a result list are normally sorted in order of relevance.
It is possible to specify different sort parameters by using the Sort
parameters dialog (located in the Tools menu).
The tool sorts a specified number of the most relevant documents in the
result list, according to specified criteria. The currently available
criteria are date and mime type.
The sort parameters stay in effect until they are explicitly reset, or the
program exits. An activated sort is indicated in the result list header.
Sort parameters are remembered between program invocations, but result
sorting is normally always inactive when the program starts. It is
possible to keep the sorting activation state between program invocations
by checking the Remember sort activation state option in the preferences.
----------------------------------------------------------------------
3.11. Search tips, shortcuts
Term completion. Typing Esc Space in the simple search entry field while
entering a word will either complete the current word if its beginning
matches a unique term in the index, or open a window to propose a list of
completions.
Picking up new terms from result or preview text. Double-clicking on a
word in the result list or in a preview window will copy it to the simple
search entry field.
Disabling stem expansion. Entering a capitalized word in any search field
will prevent stem expansion (no search for gardening if you enter Garden
instead of garden). This is the only case where character case should make
a difference for a Recoll search. You can also disable stem expansion or
change the stemming language in the preferences.
Phrases. A phrase can be looked for by enclosing it in double quotes.
Example: "user manual" will look only for occurrences of user immediately
followed by manual. You can use the This exact phrase field of the
advanced search dialog to the same effect. Phrases can be entered along
simple terms in all simple or advanced search entry fields (except This
exact phrase).
Browsing the result list inside a preview window (1.5). Entering
Shift-Down or Shift-Up (Shift + an arrow key) in a preview window will
display the next or the previous document from the result list. Any
secondary search currently active will be executed on the new document.
Forced opening of a preview window (1.6). You can use Shift+Click on a
result list Preview link to force the creation of a preview window instead
of a new tab in the existing one.
AutoPhrases (1.5). This option can be set in the preferences dialog. If it
is set, a phrase will be automatically built and added to simple searches
when looking for Any terms. This will not change radically the results,
but will give a relevance boost to the results where the search terms
appear as a phrase. Ie: searching for virtual reality will still find all
documents where either virtual or reality or both appear, but those which
contain virtual reality should appear sooner in the list.
Finding related documents. Selecting the Find similar documents entry in
the result list paragraph right-click menu will select a set of
"interesting" terms from the current result, and insert them into the
simple search entry field. You can then possibly edit the list and start a
search to find documents which may be apparented to the current result.
File names. File names are added as terms during indexing, and you can
specify them as ordinary terms in normal search fields (Recoll used to
index all directories in the file path as terms. This has been abandoned
as it did not seem really useful). Alternatively, you can use the specific
file name search which will only look for file names and can use wildcard
expansion.
Query explanation. You can get an exact description of what the query
looked for, including stem expansion, and Boolean operators used, by
clicking on the result list header.
Closing previews. Entering ^W in a tab will close it (and, for the last
tab, close the preview window). Entering Esc will close the preview window
and all its tabs.
Quitting. Entering ^Q almost anywhere will close the application.
----------------------------------------------------------------------
3.12. Customizing the search interface
It is possible to customize some aspects of the search interface by using
Query configuration entry in the Preferences menu.
There are two tabs in the dialog, dealing with the interface itself, and
with the parameters used for searching and returning results.
User interface parameters:
* Number of results in a result page
* Result list font: There is quite a lot of information shown in the
result list, and you may want to customize the font and/or font size.
The rest of the fonts used by Recoll are determined by your generic QT
config (try the qtconfig command.
* Result paragraph format string: allows you to change the presentation
of each result list entry. This is a qt-html string where the
following printf-like % substitutions will be performed:
* %A. Abstract
* %D. Date
* %I. Icon image name
* %K. Keywords (if any)
* %L. Preview and Edit links
* %M. Mime type
* %N. result Number
* %R. Relevance percentage
* %S. Size information
* %T. Title
* %U. Url
The default value for the string is:
<img src="%I" align="left">%R %S %L <b>%T</b><br>
%M %D <i>%U</i><br>
%A %K
You may, for example, try the following for a more web-like
experience:
<u><b><a href="P%N">%T</a></b></u><br>
%A<font color=#008000>%U - %S</font> - %L
Or the clean looking:
<img src="%I" align="left">%L <font color="#900000">%R</font>
<b>%T</b><br>%S
<font color="#808080"><i>%U</i></font>
<table bgcolor="#e0e0e0">
<tr><td><div>%A</div></td></tr>
</table>%K
The format of the Preview and Edit links is <a href="Pdocnum"> and <a
href="Edocnum"> where docnum is what %N would print. This makes the
title a preview link in the above format.
Please note that, due to the way the program handles right mouse
clicks in the result list, if the custom formatting results in
multiple paragraphs per result, right clicks will only work inside the
first one.
* HTML help browser: this will let you chose your preferred browser
which will be started from the Help menu to read the user manual. You
can enter a simple name if the command is in your PATH, or browse for
a full pathname.
* Auto-start simple search on white space entry: if this is checked, a
search will be executed each time you enter a space in the simple
search input field. This lets you look at the result list as you enter
new terms. This is off by default, you may like it or not...
* Start with advanced search dialog open and Start with sort dialog
open: If you use these dialogs all the time, checking these entries
will get them to open when recoll starts.
* Use desktop preferences to choose document editor: if this is checked,
the xdg-open utility will be used to open files when you click the
Edit link in the result list, instead of the application defined in
mimeview. xdg-open will in term use your desktop preferences to choose
an appropriate application.
Search parameters:
* Stemming language: stemming obviously depends on the document's
language. This listbox will let you chose among the stemming databases
which were built during indexing (this is set in the main
configuration file), or later added with recollindex -s (See the
recollindex manual). Stemming languages which are dynamically added
will be deleted at the next indexing pass unless they are also added
in the configuration file.
* Dynamically build abstracts: this decides if Recoll tries to build
document abstracts when displaying the result list. Abstracts are
constructed by taking context from the document information, around
the search terms. This can slow down result list display significantly
for big documents, and you may want to turn it off.
* Replace abstracts from documents: this decides if we should synthesize
and display an abstract in place of an explicit abstract found within
the document itself.
* Synthetic abstract size: adjust to taste...
* Synthetic abstract context words: how many words should be displayed
around each term occurrence.
External indexes: This panel will let you browse for additional indexes
that you may want to search. External indexes are designated by their
database directory (ie: /home/someothergui/.recoll/xapiandb,
/usr/local/recollglobal/xapiandb).
Once entered, the indexes will appear in the External indexes list, and
you can chose which ones you want to use at any moment by checking or
unchecking their entries.
Your main database (the one the current configuration indexes to), is
always implicitly active. If this is not desirable, you can set up your
configuration so that it indexes, for example, an empty directory.
----------------------------------------------------------------------
Chapter 4. Installation
4.1. Installing a prebuilt copy
Recoll binary packages from the Recoll web site are always linked
statically to the Xapian libraries, and have no other dependencies. You
will only have to check or install supporting applications for the file
types that you want to index beyond text, HTML and mail files, and maybe
have a look at the configuration section (but this may not be necessary
for a quick test with default parameters).
----------------------------------------------------------------------
4.1.1. Installing through a package system
If you use a BSD-type port system or a prebuilt package (RPM or other),
just follow the usual procedure for your system.
----------------------------------------------------------------------
4.1.2. Installing a prebuilt Recoll
The unpackaged binary versions on the Recoll web site are just compressed
tar files of a build tree, where only the useful parts were kept
(executables and sample configuration).
The executable binary files are built with a static link to libxapian and
libiconv, to make installation easier (no dependencies).
After extracting the tar file, you can proceed with installation as if you
had built the package from source (that is, just type make install). The
binary trees are built for installation to /usr/local.
----------------------------------------------------------------------
4.2. Supporting packages
Recoll uses external applications to index some file types. You need to
install them for the file types that you wish to have indexed (these are
run-time dependencies. None is needed for building Recoll):
* Openoffice: supported natively, but needs the unzip command to be
installed.
* PDF: pdftotext is part of the Xpdf package.
* Postscript: pstotext.
* MS Word: antiword.
* MS Excel and PowerPoint: catdoc.
* Wordperfect files: libwpd.
* RTF: unrtf
* dvi: dvips
* djvu: DjVuLibre
* MP3: Recoll will use the id3info command from the id3lib package to
extract tag information. Without it, only the file names will be
indexed.
* Pictures: Recoll uses the Exiftool Perl package to extract tag
information. Most image file formats are supported.
Text, HTML, mail folders Openoffice and Scribus files are processed
internally. Lyx is used to index Lyx files. Many filters need sed and awk.
----------------------------------------------------------------------
4.3. Building from source
4.3.1. Prerequisites
At the very least, you will need to download and install the xapian core
package (Recoll 1.9 normally uses version 1.0.2, but any 0.9 or 1.0.x
version will work too), and the qt run-time and development packages
(Recoll development currently uses version 3.3.5, but any 3.3 version is
probably OK).
You will most probably be able to find a binary package for qt for your
system. You may have to compile Xapian but this is not difficult (if you
are using FreeBSD, there is a port).
You may also need libiconv. Recoll currently uses version 1.9 (this should
not be critical). On Linux systems, the iconv interface is part of libc
and you should not need to do anything special.
----------------------------------------------------------------------
4.3.2. Building
Recoll has been built on Linux (redhat7.3, mandriva 2005/6, Fedora Core
3/4/5/6), FreeBSD 5/6, macosx, and Solaris 8. If you build on another
system, and need to modify things, I would very much welcome patches.
Depending on the qt configuration on your system, you may have to set the
QTDIR and QMAKESPECS variables in your environment:
* QTDIR should point to the directory above the one that holds the qt
include files (ie: if qt.h is /usr/local/qt/include/qt.h, QTDIR should
be /usr/local/qt).
* QMAKESPECS should be set to the name of one of the qt mkspecs
sub-directories (ie: linux-g++).
On many Linux systems, QTDIR is set by the login scripts, and QMAKESPECS
is not needed because there is a default link in mkspecs/.
Configure options: --without-aspell will disable the code for phonetic
matching of search terms. --with-fam or --with-inotify will enable the
code for real time indexing. Inotify support is enabled by default on
recent Linux systems.
Normal procedure:
cd recoll-xxx
configure
make
(practices usual hardship-repelling invocations)
There little auto-configuration. The configure script will mainly link one
of the system-specific files in the mk directory to mk/sysconf. If your
system is not known yet, it will tell you as much, and you may want to
manually copy and modify one of the existing files (the new file name
should be the output of uname -s).
----------------------------------------------------------------------
4.3.3. Installation
Either type make install or execute recollinstall prefix, in the root of
the source tree. This will copy the commands to prefix/bin and the sample
configuration files, scripts and other shared data to prefix/share/recoll.
If the installation prefix given to recollinstall is different from what
was specified when executing configure, you will have to set the
RECOLL_DATADIR environment variable to indicate where the shared data is
to be found.
You can then proceed to configuration.
----------------------------------------------------------------------
4.4. Configuration overview
Most of the parameters specific to the recoll GUI are set through the
Preferences menu and stored in the standard QT place ($HOME/.qt/recollrc).
You probably do not want to edit this by hand.
For other options, Recoll uses text configuration files. You will have to
edit them by hand for now (there is still some hope for a GUI
configuration tool in the future). The most accurate documentation for the
configuration parameters is given by comments inside the default files,
and we will just give a general overview here.
There are two sets of configuration files. The system-wide files are kept
in a directory named like /usr/[local/]share/recoll/examples, they define
default values for the system. A parallel set of files exists by default
in the .recoll directory in your home. This directory can be changed with
the RECOLL_CONFDIR environment variable or the -c option parameter to
recoll and recollindex.
If the .recoll directory does not exist when recoll or recollindex are
started, it will be created with a set of empty configuration files.
recoll will give you a chance to edit the configuration file before
starting indexing. recollindex will proceed immediately. To avoid
mistakes, the automatic directory creation will only occur for the default
location, not if -c or RECOLL_CONFDIR were used (in the latter cases, you
will have to create the directory).
All configuration files share the same format. For example, a short
extract of the main configuration file might look as follows:
# Space-separated list of directories to index.
topdirs = ~/docs /usr/share/doc
[~/somedirectory-with-utf8-txt-files]
defaultcharset = utf-8
There are three kinds of lines:
* Comment (starts with #) or empty.
* Parameter affectation (name = value).
* Section definition ([somedirname]).
Section definitions allow redefining some parameters for a directory
sub-tree. They stay in effect until another section definition, or the end
of file, is encountered. Some of the parameters used for indexing are
looked up hierarchically from the current directory location upwards. Not
all parameters can be meaningfully redefined, this is specified for each
in the next section.
When found at the beginning of a file path, the tilde character (~) is
expanded to the name of the user's home directory, as a shell would do.
White space is used for separation inside lists. List elements with
embedded spaces can be quoted using double-quotes.
----------------------------------------------------------------------
4.4.1. Main configuration file
recoll.conf is the main configuration file. It defines things like what to
index (top directories and things to ignore), and the default character
set to use for document types which do not specify it internally.
The default configuration will index your home directory. If this is not
appropriate, start recoll to create a blank configuration, click Cancel,
and edit the configuration file before restarting the command. This will
start the initial indexing, which may take some time.
Paramers:
topdirs
Specifies the list of directories or files to index (recursively
for directories). The indexer will not follow symbolic links
inside the indexed trees by default (see the followLinks options
though).
dbdir
The name of the Xapian data directory. It will be created if
needed when the index is initialized. If this is not an absolute
path, it will be interpreted relative to the configuration
directory. The value can have embedded spaces but starting or
trailing spaces will be trimmed. You cannot use quotes here.
skippedNames
A space-separated list of patterns for names of files or
directories that should be completely ignored. The list defined in
the default file is:
skippedNames = #* bin CVS Cache cache* caughtspam tmp .thumbnails .svn \
*~ recollrc
The list can be redefined for sub-directories, but is only
actually changed for the top level ones in topdirs.
The top-level directories are not affected by this list (that is,
a directory in topdirs might match and would still be indexed).
The list in the default configuration does not exclude hidden
directories (names beginning with a dot), which means that it may
index quite a few things that you do not want. On the other hand,
mail user agents like thunderbird usually store messages in hidden
directories, and you probably want this indexed. One possible
solution is to have .* in skippedNames, and add things like
~/.thunderbird or ~/.evolution in topdirs.
skippedPaths and daemSkippedPaths
A space-separated list of patterns for paths of files or
directories that should be skipped. There is no default in the
sample configuration file, but the code always adds the
configuration and database directories in there.
skippedPaths is used both by batch and real time indexing.
daemSkippedPaths can be used to specify things that should be
indexed at startup, but not monitored.
Example of use for skipping text files only in a specific
directory:
skippedPaths = ~/somedir/*.txt
followLinks
Specifies if the indexer should follow symbolic links while
walking the file tree. The default is to ignore symbolic links to
avoid multiple indexing of linked files. No effort is made to
avoid duplication when this option is set to true. This option can
be set individually for each of the topdirs members by using
sections. It can not be changed below the topdirs level.
loglevel,daemloglevel
Verbosity level for recoll and recollindex. A value of 4 lists
quite a lot of debug/information messages. 2 only lists errors.
The daemversion is specific to the indexing monitor daemon.
logfilename, daemlogfilename
Where the messages should go. 'stderr' can be used as a special
value, and is the default. The daemversion is specific to the
indexing monitor daemon.
indexstemminglanguages
A list of languages for which the stem expansion databases will be
built. See recollindex(1) or use the recollindex -l command for
possible values. You can add a stem expansion database for a
different language by using recollindex -s, but it will be deleted
during the next indexing. Only languages listed in the
configuration file are permanent.
defaultcharset
The name of the character set used for files that do not contain a
character set definition (ie: plain text files). This can be
redefined for any sub-directory. If it is not set at all, the
character set used is the one defined by the nls environment
(LC_ALL, LC_CTYPE, LANG), or iso8859-1 if nothing is set.
maxfsoccuppc
Maximum file system occupation before we stop indexing. The value
is a percentage, corresponding to what the "Capacity" df output
column shows. The default value is 0, meaning no checking.
idxflushmb
Threshold (megabytes of new text data) where we flush from memory
to disk index. Setting this can help control memory usage. A value
of 0 means no explicit flushing, letting Xapian use its own
default, which is flushing every 10000 documents (memory usage
depends on average document size). The default value is 10.
filtersdir
A directory to search for the external filter scripts used to
index some types of files. The value should not be changed, except
if you want to modify one of the default scripts. The value can be
redefined for any sub-directory.
iconsdir
The name of the directory where recoll result list icons are
stored. You can change this if you want different images.
guesscharset
Decide if we try to guess the character set of files if no
internal value is available (ie: for plain text files). This does
not work well in general, and should probably not be used.
usesystemfilecommand
Decide if we use the file -i system command as a final step for
determining the mime type for a file (the main procedure uses
suffix associations as defined in the mimemap file). This can be
useful for files with suffix-less names, but it will also cause
the indexing of many bogus "text" files.
indexallfilenames
Recoll indexes file names in a special section of the database to
allow specific file names searches using wild cards. This
parameter decides if file name indexing is performed only for
files with mime types that would qualify them for full text
indexing, or for all files inside the selected subtrees,
independently of mime type.
idxabsmlen
Recoll stores an abstract for each indexed file inside the
database. The text can come from an actual 'abstract' section in
the document or will just be the beginning of the document. It is
stored in the index so that it can be displayed inside the result
lists without decoding the original file. The idxabsmlen parameter
defines the size of the stored abstract. The default value is 250
bytes. The search interface gives you the choice to display this
stored text or a synthetic abstract built by extracting text
around the search terms. If you always prefer the synthetic
abstract, you can reduce this value and save a little space.
aspellLanguage
Language definitions to use when creating the aspell dictionary.
The value must match a set of aspell language definition files.
You can type "aspell config" to see where these are installed
(look for data-dir). The default if the variable is not set is to
use your desktop national language environment to guess the value.
noaspell
If this is set, the aspell dictionary generation is turned off.
Useful for cases where you don't need the functionality or when it
is unusable because aspell crashes during dictionary generation.
----------------------------------------------------------------------
4.4.2. The mimemap file
mimemap specifies the file name extension to mime type mappings.
For file names without an extension, or with an unknown one, the system's
file -i command will be executed to determine the mime type (this can be
switched off inside the main configuration file).
The mappings can be specified on a per-subtree basis, which may be useful
in some cases. Example: gaim logs have a .txt extension but should be
handled specially, which is possible because they are usually all located
in one place.
mimemap also has a recoll_noindex variable which is a list of suffixes.
Matching files will be skipped (which avoids unnecessary decompressions or
file executions). This is partially redundant with skippedNames in the
main configuration file, with two differences: it will not affect
directories, and it cannot be made dependant on the file-system location
(it is a configuration-wide parameter). You could accomplish with
skippedNames anything that recoll_noindex does. The latter is used mostly
for things known to be unindexable by a given Recoll version. Having it
there avoids cluttering the more user-oriented and locally customized
skippedNames.
----------------------------------------------------------------------
4.4.3. The mimeconf file
mimeconf specifies how the different mime types are handled for indexing,
and which icons are displayed in the recoll result lists.
Changing the parameters in the [index] section is probably not a good idea
except if you are a Recoll developer.
The [icons] section allows you to change the icons which are displayed by
recoll in the result lists (the values are the basenames of the png images
inside the iconsdir directory (specified in recoll.conf).
----------------------------------------------------------------------
4.4.4. The mimeview file
mimeview specifies which programs are started when you click on an Edit
link in a result list. Ie: HTML is normally displayed using firefox, but
you may prefer Konqueror, your openoffice.org program might be named
oofice instead of openoffice etc.
Changes to this file can be done by direct editing, or through the recoll
user preferences dialog.
As for the other configuration files, the normal usage is to have a
mimeview inside your own configuration directory, with just the
non-default entries, which will override those from the central
configuration file.
Please note that these entries must be placed under a [view] section.
If Use desktop preferences to choose document editor is checked in the
user preferences, all mimeview entries will be ignored except the one
labelled application/x-all (which is set to use xdg-open by default).
----------------------------------------------------------------------
4.4.5. Examples of configuration adjustments
4.4.5.1. Adding an external viewer for an non-indexed type
Imagine that you have some kind of file which does not have indexable
content, but for which you would like to have a functional Edit link in
the result list (when found by file name). The file names end in .blob and
can be displayed by application blobviewer.
You need two entries in the configuration files for this to work:
* In $RECOLL_CONFDIR/mimemap (typically ~/.recoll/mimemap), add the
following line:
application/x-blobapp = .blob
Note that the mime type is made up here, and you could call it
diesel/oil just the same.
* In $RECOLL_CONFDIR/mimeview under the [view] section:
application/x-blobapp = blobviewer %f
We are supposing that blobviewer wants a file name parameter here, you
would use %u if it liked URLs better.
If you just wanted to change the application used by Recoll to display a
mime type which it already knows, you would just need to edit mimeview.
The entries you add in your personal file override those in the central
configuration, which you do not need to alter
----------------------------------------------------------------------
4.4.5.2. Adding indexing support for a new file type
Let us now imagine that the above .blob files actually contain indexable
text and that you know how to extract it with a command line program.
Getting Recoll to index the files is easy. You need to perform the above
alteration, and also to add data to the mimeconf file (typically in
~/.recoll/mimeconf):
* Under the [index] section, add the following line (more about the
rclblob indexing script later):
application/x-blobapp = exec rclblob
* Under the [icons] section, you should choose an icon to be displayed
for the files inside the result lists. Icons are normally 64x64 pixels
PNG files which live in /usr/[local/]share/recoll/images.
* Under the [categories] section, you should add the mime type where it
makes sense (you can also create a category). Categories may be used
for filtering in advanced search.
The rclblob filter should be an executable program or script which exists
inside /usr/[local/]share/recoll/filters. It will be given a file name as
argument and should output the text contents in html format on the
standard output.
You can find more details about writing a Recoll filter in the section
about writing filters
----------------------------------------------------------------------
4.5. Extending Recoll
4.5.1. Writing a document filter
Recoll filters are executable programs which translate from a specific
format (ie: openoffice, acrobat, etc.) to the Recoll indexing input
format, which was chosen to be HTML.
Recoll filters are usually shell-scripts, but this is in no way necessary.
These programs are extremely simple and most of the difficulty lies in
extracting the text from the native format, not outputting what is
expected by Recoll. Happily enough, most document formats already have
translators or text extractors which handle the difficult part and can be
called from the filter.
Filters are called with a single argument which is the source file name.
They should output the result to stdout.
The RECOLL_FILTER_FORPREVIEW environment variable (values yes, no) tells
the filter if the operation is for indexing or previewing. Some filters
use this to output a slightly different format. This is not essential.
The output HTML could be very minimal like the following example:
<html><head>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
</head>
<body>some text content</body></html>
You should take care to escape some characters inside the text by
transforming them into appropriate entities. "&" should be transformed
into "&", "<" should be transformed into "<".
The character set needs to be specified in the header. It does not need to
be UTF-8 (Recoll will take care of translating it), but it must be
accurate for good results.
Recoll will also make use of other header fields if they are present:
title, description, keywords.
As of Recoll release 1.9, filters also have the possibility to "invent"
field names. This should be output as meta tags:
<meta name="somefield" content="Some textual data" />
In this case, a correspondance between field name and Xapian prefix should
also be added to the mimeconf file. See the existing entries for
inspiration. The field can then be used inside the query language to
narrow searches.
The easiest way to write a new filter is probably to start from an
existing one.
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dockes