CM_PERL(7) claws-mail-perl-filter CM_PERL(7)

cm_perl -- A Perl Plugin for Claws Mail

This plugin provides an extended filtering engine for the email client Claws Mail. It allows for the use of full Perl power in email filters.

To get started, you can use the matcherrc2perlfilter.pl script in the tools-directory to translate your old filtering rules to Perl. Simply execute the script and follow the instructions. (note that with recent versions of Claws Mail, this script might not work due to upstream syntax changes. This will get updated in the future. Send me an email if you have problems getting started).

However, you might want to consider reading the rest of this manual and rewriting your rules if you choose to use the plugin, since the Perl code produced by this script is not exactly pretty.

Don't speak Perl? No problem, "perldoc perlintro" should give you enough information to do fancy stuff.

The Perl plugin expects a Perl script file called perl_filter in Claws Mail' config directory (usually $HOME/.claws-mail -- try `claws-mail --config-dir' if you're unsure). If that file doesn't exist on plugin start, an empty one is created. This file, which doesn't need to start with a sha-bang (!#/bin/perl), holds the Perl instructions for your email filters. To encourage some good manners, the code is executed in a "use strict;" environment.

Both Claws Mail' filtering conditions and actions are mapped to Perl functions with corresponding names, wherever this is possible.

For a detailed function description, see section "FUNCTION DESCRIPTIONS", below.

 all, marked, unread, deleted, new, replied,
 forwarded, locked, ignore_thread, colorlabel,
 match, matchcase, regexp, S<regexpcase, test,
 size_greater, size_smaller, size_equal,
 score_greater, score_lower, score_equal, age_greater,
 age_lower, partial, tagged
    
 mark, unmark, dele, mark_as_unread, mark_as_read,
 lock, unlock, move, copy, color, execute,
 hide, set_score, change_score, stop, forward,
 forward_as_attachment, redirect, set_tag, unset_tag,
 clear_tags
    
 header, body, filepath, extract_addresses,
 move_to_trash, abort, addr_in_addressbook,
 from_in_addressbook, get_attribute_value, SA_is_spam,
 exit, manual, make_sure_folder_exists,
 filter_log, filter_log_verbosity,
 make_sure_tag_exists

In general, after the filtering invoked by the Perl script, the mail is passed on to Claws' internal filtering engine, unless a final rule was hit. Final rules stop not only the Perl filtering script at the point of their occurrence, but also prevent processing that email by Claws' internal filtering engine (this might sound confusing, but you are already familiar with that concept from standard filters: After an email was e.g. moved, the following rules don't apply anymore).

Also, be careful with the way you quote. In particular, remember that the @-sign has a special meaning in Perl, and gets interpolated inside double quotes. See "Quote and Quote-like Operators" in perlop to learn more about quoting and interpolation.

Returns a true value. Available for completeness only.
Returns a true value if the marked flag is set, false otherwise.
Returns a true value if the unread flag is set, false otherwise.
Returns a true value if the deleted flag is set, false otherwise.
Returns a true value if the new flag is set, false otherwise.
Returns a true value if the replied flag is set, false otherwise.
Returns a true value if the forwarded flag is set, false otherwise.
Returns a true value if the locked flag is set, false otherwise.
Returns a true value if the "Ignore Thread" flag is set, false otherwise.
colorlabel COLOR
Returns a true value if message has the color COLOR. COLOR can be either a numeric value between 0 and 7 (with colors corresponding to the internal filtering engine), or the english color name as it is introduced in the filtering dialog (that is, one of: none, orange, red, pink, sky blue, blue, green or brown, while upper and lower case letters make no difference). If COLOR is omitted, 0 (none) is assumed.
Returns a true value if message size is greater than SIZE, false otherwise.
Returns a true value if message size is smaller than SIZE, false otherwise.
Returns a true value if message size is equal to SIZE, false otherwise.
Returns a true value if message score is greater than SCORE, false otherwise.
Returns a true value if message score is lower than SCORE, false otherwise.
Returns a true value if message score is equal to SCORE, false otherwise.
Returns a true value if message age is greater than AGE, false otherwise.
Returns a true value if message age is lower than AGE, false otherwise.
Returns a true value if message has only partially been downloaded, false otherwise.
Returns a true value if the messages has one or more tags.
Corresponds the 'test' internal filtering rule. In particular, it accepts the same symbols, namely:
%%
%
%s
Subject
%f
From
%t
To
%c
Cc
%d
Date
%i
Message-ID
%n
Newsgroups
%r
References
%F
Filename -- should not be modified
The matching functions have a special syntax. The first argument is either any of to_or_cc, body_part, headers_part, headers_cont, message, to, from, subject, cc, newsgroups, inreplyto, references, or tag (those strings may or may not be quoted), the pattern matching works on that area. If it is any other string (which must then be quoted), this string is taken to be the name of a header field.

The second argument is the string to look for. For match, matchcase, regexp and regexpcase we have case sensitive normal matching, case insensitive normal matching, case sensitive regular expression matching and case insensitive regular expression pattern matching, respectively.

The functions return true if the pattern was found, false otherwise.

Just as with the built-in filtering engine, the message body is searched and provided as is - no character-set analysis is done. Likewise, no HTML-tags are stripped. It should be possible to use external modules or programs for these tasks though. If you're doing that, drop me a message with your experiences.

With Perl having its strengths in pattern matching, using Perl's builtin operators are usually a better option than using these functions.

The actions return a true value upon success, and 'undef' when an error occurred. Final message rules are indicated. (See above for a sketch what a final rule is)

Mark the message.
Unmark the message.
Delete the message. Note the name change of Claws Mail' "delete" to "dele". This is because "delete" is one of Perl's builtin commands which cannot be redefined (if it can, tell me how).

This is a final rule.

Mark the message as read
Mark the message as unread
Lock the message
Remove the message lock
Move the message to folder DESTINATION. The folder notation is the same that Claws Mail uses. You can copy & paste from the move dialog of the normal filtering, until you get a feeling for the notation.

This is a final rule.

Copy the message to folder DESTINATION. The folder notation is the same that Claws Mail uses. You can copy & paste from the move dialog of the normal filtering, until you get a feeling for the notation.
This is the same as the test - rule from section "Standard Filtering Conditions" execpt that it always returns a true value.
Hide the message
Set message score to SCORE
Change message score by SCORE
Stop Perl script at this point. Note that this is not a final rule, meaning that the email gets passed on to the internal filtering engine. See "abort" below if you don't want that.
Forward the message to email address EMAIL, using the account ID ACCOUNT as sender account. So far, you have to create a rule in the normal filtering engine to find out that number.
Forward the message to email address EMAIL in an attachment, using the account ID ACCOUNT as sender account. So far, you have to create a rule in the normal filtering engine to find out that number.
Redirect the message to EMAIL, using the account ID ACCOUNT as sender account. So far, you have to create a rule in the normal filtering engine to find out that number.
Apply tag TAG. TAG must exist.
Unset tag TAG.
Clear all tags.

Functions

header ARG
If ARG is not given, returns a list of all header field names of the mail.

If ARG is given, returns 'undef' if the header field ARG does not exist in the email. Otherwise, it returns

The value of the header field ARG.
A list of all available header field values. This is useful if a header field occurs more than once in an email (eg the Received - header).

The header field "References" forms a special case. In a scalar context, it returns the first reference. In a list context, it returns a list of all references.

Returns the email body in a scalar.
Returns the file and path of the email that is currently filtered (corresponds to the %F arguemnt in the 'test' rule).
Extracts email addresses from a string and gives back a list of addresses found. Currently an email address is found using the regular expression '[-.+\w]+\@[-.+\w]+'. This will not find all valid email addresses. Feel free to send me a better regexp.
Move the email message to default trash folder.

This is a final rule.

Stop Perl script at this point.

In contrast to 'stop', this is a final rule.

Returns a true value if the email address EMAIL is in the addressbook with the name ADDRESSBOOK. If ADDRESSBOOK is not given, returns true if the email address is in any addressbook.
from_in_addressbook ADDRESSBOOK
Checks if the email address found in the From-header is in addressbook ADDRESSBOOK (or any, if omitted). It is implemented as 

 my ($from) = extract_addresses(header("from"));
 return 0 unless $from;
 return addr_in_addressbook($from,@_);

so the same restrictions as to extract_addresses apply.

Looks through the addressbook ADDRESSBOOK (or all addressbooks, if omitted) for a contact with the an email address EMAIL. If found, the function checks if this contact has a user attribute with name ATTRIBUTE. It returns the value of this attribute, or an empty string if it was not found. As usual, 'undef' is returned if an error occurred.
Is an alias to

not test 'spamc -c < %F > /dev/null'

Has been redefined to be an alias to 'stop'. You shouldn't use Perl's own 'exit' command, since it would exit Claws Mail.
Returns a true value if the filter script was invoked manually, that is, via the Tools menu.
Returns a true value if the folder with id IDENTIFIER (e.g. #mh/Mail/foo/bar) exists or could be created.
Returns a true value if the tag TAG exists or could be created.
Writes TEXT to the filter logfile. SECTION can be any of
  • "LOG_MANUAL"
  • "LOG_MATCH"
  • "LOG_ACTION"

If the SECTION is omitted, "LOG_MANUAL" is assumed.

filter_log_verbosity VERBOSITY
Changes the filter log verbosity for the current mail. VERBOSITY must be any of
0
Be silent
1
Log MANUAL type
2
Log Action type
3
Log MATCH type

For the meaning of those numbers, read section "LOGGING". If VERBOSITY is omitted, the filter logfile verbosity is not changed.

This function returns the filter_log_verbosity number before the change (if any).

Variables

$permanent
This scalar keeps its value between filtered mail messages. On plugin start, it is initialized to the empty string.

To keep track of what has been done to the mails while filtering, the plugin supports logging. Three verbosity levels are recognized:

0
logging disabled
1
log only manual messages, that is, messages introduced by the "filter_log" command in filter scripts
2
log manual messages and filter actions
3
log manual messages, filter actions and filter matches

The messages are logged in Claws Mail' log window. The default log level is 2. Log level 3 is not recommended, because the matcher functions log a message if they succeeded, and thus, if you have negative checks, you'll get confusing entries. If you want to keep track of matching, do it manually, using "filter_log", or do it by temporary enabling matcher logging using "filter_log_verbosity".

The first time you unload this plugin (or shut down Claws Mail), a section called [PerlPlugin] will be created in Claws Mail' configuration file clawsrc, containing one variable:

 * filter_log_verbosity

If you want to change the default behaviour, you can edit this line. Make sure Claws Mail is not running while you do this.

It will be possible to access these setting via the GUI, as soon as I find the time to write a corresponding GTK plugin, or somebody else is interested in contributing that.

This section lists a small example of a Perl script file. I'm sure you get the idea..

 #-8<----------------------------------------------------
 # -*- perl -*-
 # local functions
 # Learn ham messages, and move them to specified folder. This is
 # useful for making sure a bayes filter sees ham as well.
 sub learn_and_move {
     execute('put command to learn ham here');
     move(@_);
 }
 # Two-stage spam filter. Every email that scores higher than 15
 # on SpamAssassin gets moved into the default trash folder.
 # All mails lower than that, but higher than SpamAssassin's
 # 'required_hits' go into  #mh/mail/Spam.
 sub spamcheck {
     my $surely_spam = 15;
     my $filepath = filepath;
     my $spamc = `spamc -c < $filepath`;
     my ($value,$threshold) = ($spamc =~ m|([-.,0-9]+)/([-.,0-9]+)|);
     if($value >= $surely_spam) {
        mark_as_read;
        move_to_trash;
     }
     if($value >= $threshold) {mark_as_read; move '#mh/mail/Spam';}
 }
 # Perl script execution starts here.
 # Some specific sorting
 learn_and_move '#mh/mail/MailLists/Claws Mail/user'
   if matchcase('sender','claws-mail-users-admin@lists.sourceforge.net');
 learn_and_move '#mh/mail/MailLists/Sylpheed'
   if matchcase('list-id','sylpheed.good-day.net');
 # Implement incoming folders using addressbook
 # attributes. Target folders for specific email addresses are
 # stored directly in the addressbook. This way, if an email
 # address changes, we only have to update the addressbook, not
 # the filter rules! Besides that, we can greatly unclutter the
 # filter script.
 # get the email address in the from header
 my $fromheader = header "from";
 my ($from) = extract_addresses $fromheader;
 # check if this email address has an associated attribute
 # called "incoming_folder". If if has, the value of this
 # attribute is supposed to be the target folder.
 my $value = get_attribute_value $from, "incoming_folder";
 learn_and_move($value) if $value;
 # An example of a whitelist: If the from-address is in my
 # "office" addressbook, move the mail to folder #mh/mail/office
 learn_and_move '#mh/mail/office' if from_in_addressbook("office");
 # If the from-address is in any other addressbook, move the
 # mail to folder #mh/mail/inbox/known
 learn_and_move '#mh/mail/inbox/known' if from_in_addressbook;
 # Feed the remaining mails through SpamAssassin.
 spamcheck;
 # mails that make it to the end of the script are passed on to
 # the internal filtering engine. If the internal rules don't say
 # otherwise, the mails end up in the default inbox.
 #-8<----------------------------------------------------

Please report comments, suggestions and bugreports to the address given in the "AUTHOR" section of this document.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

claws-mail(1), perl(1)

Holger Berndt <berndth@gmx.de>

2024-03-31 4.2.0-2build7