Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!sample.eng.ohio-state.edu!icarus!kaul
From: kaul@icarus.eng.ohio-state.edu (Rich Kaul)
Newsgroups: comp.mail.sendmail
Subject: Re: Mail filters
Message-ID: <KAUL.91Mar16235725@icarus.eng.ohio-state.edu>
Date: 17 Mar 91 05:57:25 GMT
References: <1991Mar15.195109.12234@viewlogic.com>
Sender: kaul@ee.eng.ohio-state.edu (Rich Kaul)
Organization: The Ohio State University Dept of Electrical Engineering
Lines: 182
In-Reply-To: kenc@suntan.viewlogic.com's message of 15 Mar 91 19:51:09 GMT

In article <1991Mar15.195109.12234@viewlogic.com> kenc@suntan.viewlogic.com (Kenstir) writes:
   I'd like to set up a filter on my mail, and I'd like it
   to happen between the time sendmail gets its paws on the
   text and the time it puts the file in /usr/spool/mail.
   [...]
   2.  Set up a .forward:
	   "|/u/kenc/mail-filter2 kenc"

       And then in /u/kenc/mail-filter2:
	   awk -f foo.awk >> /usr/spool/mail/kenc

   PROBLEMS:  I'm not doing any file locking and I'm sure eventually
   I would run into race conditions.

Use a better tool.  I do a similar thing to filter my mail, but I use
perl to do the filtering and file locking.  I go further and deliver
the mail to different directories for use by GNUS to mix reading of
the tons of system mail, etc. that I get and news.  Only critical
stuff from a group of people gets through to my mailbox.  I use a
.forward that looks like:

"|/usr/1/kaul/bin/ppmd /usr/1/kaul kaul >>/usr/1/kaul/.maillog 2>&1"

and the following perl script.

-rich

#!/usr/bin/perl

# An attempt at a perl mail delivery agent.  The basic premise is
# that mail from certain people demands attention immediately, so it
# gets put in the normal system mailbox.  Mail from mailing lists is
# to be placed in various subdirectories in a format that GNUS can
# handle for reading.  Mail from the system, random users, etc, gets
# placed in a third directory ($root).  This is, of course, easily
# customizable.  Delivering into a directory requires a .last file to
# keep track of article numbers.
#
# Pardon the perl style; I'm just learning but this works!  Comments
# welcome.
#
# Author:	Rich Kaul (kaul@icarus.eng.ohio-state.edu)
# Date:		11/13/90
# The credit where credit is due department:  the core of the message
# parsing is based on Larry Wall's mailagent script, although the rest
# of this ugly mess (which nobody else would want to claim) is mine.

($HOME, $USER) = @ARGV;

$root = "$HOME/Memos/personal";		# root of personal news tree.
$dest = $root;
$box = "/usr/spool/mail/$USER";		# default mail box.
$GIVE_UP_BOX = "$HOME/mail_dump";	# emergency dumping box.

$LOCK_SH = 1;				# Values for flock() calls.
$LOCK_EX = 2;
$LOCK_NB = 4;
$LOCK_UN = 8;

umask(077);				# Get a little privacy.

# Now run and get the headers.  We have to parse the headers before we
# can figure out delivery.
while (<stdin>) {
    # Do this on the From_ line only.
    if (1 .. 1) {
	if (/^From\s+(\S+)\s+[^\n]*(\w{3}\s+\d+\s+\d+:\d+)/) { $from = $1; }
	$from =~ s/@.*//;		# remove trailing @machine
	$from =~ s/%.*//;		# remove trailing %machine
	$from = $1 if $from =~ /.*!([^\n]+)/; # remove leading ! paths
    }

    # This section operates on the header of the message.  We create
    # an array of header keys to work on later.
    if (1 .. /^\s*$/) {
	s/^From: ([^<]*)\s+<(.*)>$/From: $2 ($1)/;	# rewrite ugly header
	$header .= $_;
	chop;
	if (/^\s*$/) {
	    foreach $key (keys(header)) {
		eval "\$H$key = \$header{'$key'}";
	    }
	}
	else {
	    if (s/^([-\w]+):\s*//) {
		($headline = $1) =~ y/A-Z-/a-z_/;
		$header{$headline} .= "\n" if $header{$headline} ne '';
	    }
	    else {
		s/^\s+/ /;
	    }
	    $header{$headline} .= $_;
	}
    }
    # And here we make the body of the message.
    else {
	$body .= $_;
	}
}


# Now we list the people who can crash into the mailbox.
if($from =~ /karl_kl/ || $from =~ /alden/ || $from =~ /monty/) {$dest = $box;}
elsif($from=~/pnelson/ || $from=~/wilson/i || $from =~ /gratz/i) {$dest=$box;}
elsif($from =~ /bibyk/ || $from =~ /adkins/ || $from =~ /zaka/) {$dest = $box;}
elsif($from =~ /kaul/ || $from =~ /aspark/ || $from =~ /george/) {$dest = $box;}

# Ok, now figure out where to deliver the message.  The first case is
# mail from mailing lists.
if($from =~ /firearms/) {$dest = "$root/firearms";}
elsif($Hto =~ /firearms/i || $Hcc =~ /firearms/i ) {$dest = "$root/firearms";}
elsif($from =~ /freemacs/) {$dest = "$root/freemacs";}
elsif ($Hto =~ /gif/ || $Hcc =~ /gif/) {$dest = "$root/gif";}
elsif($Hto =~ /gnuplot/ || $Hcc =~ /gnuplot/) {$dest = "$root/gnuplot";}
elsif ($Hto =~ /freemacs/ || $Hcc =~ /freemacs/) {$dest = "$root/freemacs";}
elsif ($Hto =~ /interviews/i || $Hcc =~ /interviews/i ) { 
    $dest = "$root/interviews";}
elsif ($Hto =~ /vem/i || $Hto =~ /oct/i || $Hcc =~ /vem/i || $Hcc =~ /oct/i) {
    $dest = "$root/vem";}
elsif($Hto =~ /xviewbug-trackers/ || $Hcc =~ /xviewbug-trackers/) {
    $dest = "$root/xview";}

# Here we dump system messages.  It grows too fast and should be split
# up soon...
if($from =~ /root/ || $from =~ /news/) { $dest = "$root/system";}
elsif($Hto =~ /site/ || $Hcc =~ /site/) { $dest = "$root/system";}

# Now we do the delivery.  There are two cases.  If we are delivering
# to a directory find and update the .last file there.
if ( -d $dest ) {
    # It's going to be a news article, so change the From_ line
    $header =~ s/^From /Unix-From: /;
    $all = $header . $body;

    $count_file = "$dest/\.last";
    open(COUNTER,"+<$count_file")|| do gag("Can't open $dest/.last ($< $>): $!");
    while (<COUNTER>) {
	chop;
	$count = $_;
	$count++;
    }
    do flocker(COUNTER,$LOCK_EX);	# Lock the file, just in case.
    seek(COUNTER,0,0);
    print COUNTER $count,"\n";
    do flocker(COUNTER,$LOCK_UN);

    # We now have the article number we need.
    open(ART,">>$dest/$count") || do gag("Can't open $dest/$count ($< $>): $!");
    print ART $all,"\n";
} else {
    # Here we're delivering to a file, which is easier.  Build and deliver.
    $all = $header . $body;
    open(BOX, ">>$dest") || do gag ("Can't open $dest ($< $>): $!");

    do flocker(BOX,$LOCK_EX);
    print BOX $all,"\n\n";
    do flocker(BOX,$LOCK_UN);
}

# File locking subroutine.
sub flocker {
    local ($file, $mode) = @_;
    eval 'flock($file,$mode);';
    seek($file, 0, 2);		# in case it was appended while we were waiting
}

# For some reason mail couldn't get delivered.  Dump the message in the
# emergency mailbox and exit.
sub gag {
    open(ERR_BOX, ">>$GIVE_UP_BOX") || die "`date`: I'm really hosed.  I can't even open the emergency box $GIVE_UP_BOX\n";

    print @_;
    do flocker(ERR_BOX,$LOCK_EX);
    print ERR_BOX $all,"\n\n";
    do flocker(ERR_BOX,$LOCK_UN);
    exit 1;
}
    
-- 
Rich Kaul                         | "They that can give up essential liberty
kaul@icarus.eng.ohio-state.edu    | to obtain a little temporary safety
or ...!osu-cis!kaul		  | deserve neither liberty nor safety."