FILTER(1)						      General Commands Manual							 FILTER(1)

NAME

       filter - filter incoming messages before adding to mailbox

SYNOPSIS

       filter [-q] [-v] [-l] [-o output] [-f rules-file] [-m mailbox]
       filter [-n] [-f rules-file]
       filter [-r] [-o output] [-f rules-file]
       filter [-c] [-s] [-o output] [-f rules-file]
       filter [-c] [-S] [-o output] [-f rules-file]

DESCRIPTION

       In brief, filter is designed to sort incoming mail based on user preferences for various recognized headers.  It logs a summary of messages
       filtered to a logfile.  See the USAGE section for full details.

OPTIONS

       The flags the filter program understands are;

       -c	 Clear logs.  If this flag is used, the log files will be removed after being summarized by either "-s" or "-S" (see below).

       -f rules-file
		 Get rules from specified file instead of default $HOME/.filter/filter-rules

       -l	 Log actions only.  Do not log information about mailed messages.

       -n	 Not really.  Output what would happen if given message from standard input, but don't actually do anything with it.

       -o file	 Redirect stdout messages to the specified file or device.  Logging of filter actions is not affected.	(This  is  added  to  more
		 gracefully deal with changes in the file system (since sendmail is quite picky about modes of files being redirected into.))

       -m mailbox
		 Override the compiled in definition of your primary 'mailbox'.  This is disabled if filter is setgid.

       -q	 Quiet.  Do not log filtering actions.

       -r	 Rules.  List the rules currently being used.

       -s	 Summarize.  List a summary of the message filtering log.

       -S	 This is the same as `-s' but includes message-by-message information additionally.

       -v	 Verbose.   Give  output on standard out for each message filtered.  May be useful to set output to ``/dev/console'' or other log-
		 ging device.  (see -o).

USAGE

       Filter uses a set of selection rules to process incoming mail messages. These rules are normally read in  from  $HOME/.filter/filter-rules.
       As  soon  as  a rule matches something about the message, that rule is used, and no further action is taken.  The general format for a rule
       is;

	       if  (expression)  then  action

       where expression is:

	       expression  ::=	{ not }  condition  { and expression }

	       condition  ::=  field  =  stringvalue
			  ::=  field  != stringvalue
			  ::=  lines  relop  numvalue
       or		  ::=  always

       These further break down as:

	       field  ::=  from  |  subject  |	alphasubject  |  to  |	lines | sender

	       relop  ::=  =  |  !=  |	<  |  >  |  <=	|  >=

	       stringvalue  ::=  any  quoted  string

	       numvalue  ::=  any  integer  value

       Note: alphasubject is a transformed version of the subject line, where only alpha chars are preserved, and they are forced to  lower  case.
       It is then simpler to use a regular expression match across a wide variety of similar subjects.

       from matches any and all of the following headers:
	 "From " From: Reply-To: Sender:

       Action can be any of:

	   delete	       (ignore this message; throw it away)
	   save  foldername    (put in 'foldername' for later)
	   savecopy foldername (save a copy AND put in my inbox)
	   execute  command    (pipe message to 'command')
	   executec command    (copy to inbox, AND pipe to 'command')
	   forward  address    (forward this message)
	   forwardc address    (forward this message, AND copy to inbox)
	   resend   address    (resend to new addr without change)
	   leave	       (just put it in my inbox)
	   bounce	       (say there's no such user)

       An example of a rules file would be:

	   # I'll read this stuff later when I feel like it
	   if (from = "list@interest.org") then save "~/Mail/mailinglist"
	   # This mailing list actually has an x-mailing-list header
	   if (mailinglist = "smartlist@other.com") then save "~/Mail/otherlist"
	   # auto-archive this project's email, AND put in my current mailbox
	   if (subject = "strange project") then savecopy "~/Mail/proj-archive"
	   # If "make money" appears ANYWHERE in subject, upper/lowercase,
	   # delete the lousy spam
	   if ( subject = "make money" ) then delete
	   # This person no longer shares this virtual mailbox with me.
	   # Resend visibly as a "forwarded" message.
	   if (to = "partner") then forward "partner@new.address.com"
	   # If email for an old address comes to me, resend to new one.
	   # Note that the "envelope" will show my address, but the
	   # normal headers will not
	   if ( to = "old_address" ) then resend new@address.here"
	   # Special virtual headerline derived from normal subject line
	   # catches "multiple!!!wor+ds**here"
	   if ( alphasubject = "multiplewordshere" ) then delete
	   # If email for a special address comes to me, resend through
	   # a non-standard "special" mailer
	   if ( to = "special_address" ) then exec "/usr/lib/mailer special@addr"
	   #
	   # The rules file doesnt really need parentheses. Or even the 'if'.
	   # They are just traditional.
	   subject = "silly" then bounce

       Note that all filenames must be double-quoted

       For further information about the rules language, please see The Elm Filter Guide.

MAINTAINER

       Philip Brown

FILES

       $HOME/.filter/filter-rules Default rules file
       $HOME/.filter/filterlog	  A log of what has been done
       $HOME/.filter/filtersum	  A summary of what has been done
       $MAIL		       IF you set this var, defines your
			       default mailbox
       /etc/passwd	       Used to get users home directory

SEE ALSO

       The Elm Filter Guide (distributed with the source code)
       mail(1), mailx(1), sendmail(1,8)

COMMENTS

       Could be smarter about pattern matching. Message body checks might be nice too.

       Please note that this was historically bundled with the elm mail reader, but now can be found at
       http://www.bolthole.com/filter/

BUG REPORTS TO

       filter@bolthole.com

COPYRIGHTS

       Copyright 1988-1992 by The USENET Community Trust
       Derived from Elm 2.0,  Copyright 1986, 1987 by Dave Taylor

USENET Comm. Trust						   19 April 2004							 FILTER(1)