3 # This is a Perl script to demonstrate the possibilities of on-the-fly
4 # delivery filtering in Exim. It is presented with a message on its standard
5 # input, and must copy it to the standard output, transforming it as it
6 # pleases, but of course it must keep to the syntax of RFC 822 for the headers.
8 # The filter is run before any SMTP-specific processing, such as turning
9 # \n into \r\n and escaping lines beginning with a dot.
11 # Philip Hazel, May 1997
12 #############################################################################
15 BEGIN { pop @INC if $INC[-1] eq '.' };
18 if ($ARGV[0] eq '--version') {
19 print basename($0) . ": $0\n",
20 "build: EXIM_RELEASE_VERSIONEXIM_VARIANT_VERSION\n",
21 "perl(runtime): $]\n";
25 # If the filter is called with any arguments, insert them into the message
26 # as X-Arg headers, just to verify what they are.
28 for ($ac = 0; $ac < @ARGV; $ac++)
30 printf("X-Arg%d: %s\n", $ac, $ARGV[$ac]);
33 # Now read the header portion of the message; this is easy to do in Perl
35 $/ = ""; # set paragraph mode
36 chomp($headers = <STDIN>); # read a paragraph, remove trailing newlines
37 $/ = "\n"; # unset paragraph mode
39 # Splitting up a sequence of unique headers is easy to do in Perl, but a
40 # message may contain duplicate headers of various kinds. It is better
41 # to extract the headers one wants from the whole paragraph, do any appropriate
42 # munging, and then put them back (unless removing them altogether). Messing
43 # with "Received:" headers is not in any case to be encouraged.
45 # As a demonstration, we extract the "From:" header, add a textual comment
46 # to it, and put it back.
48 ($pre, $from, $post) =
49 $headers =~ /^(|(?:.|\n)+\n) (?# Stuff preceding the From header,
50 which is either null, or any number
51 of characters, including \n, ending
53 From:[\s\t]* (?# Header name, with optional space or tab.)
54 ((?:.|\n)*?) (?# Header body, which contains any chars,
55 including \n, but we want to make it as
56 short as possible so as not to include
57 following headers by mistake.)
58 (|\n\S(?:.|\n)*)$ (?# Header terminates at end or at \n followed
59 by a non-whitespace character and
61 /ix; # case independent, regular expression,
62 # use extended features (ignore whitespace)
64 # Only do something if there was a From: header, of course. It has been
65 # extracted without the final \n, which is on the front of the $post
70 $headers = $pre . "From: $from (this is an added comment)" . $post;
73 # Add a new header to the end of the headers; remember that the final
76 $headers .= "\nX-Comment: Message munged";
78 # Write out the processed headers, plus a blank line to separate them from
81 printf(STDOUT "%s\n\n", $headers);
83 # As a demonstration of munging the body of a message, reverse all the
84 # characters in each line.
90 printf(STDOUT "%s\n", $_);