🚀 go-pugleaf

In article <1992Jul24.184037.15528@infonode.ingr.com> fordke@infonode.ingr.com (Keith Ford) writes:
: 
: I would like to pipe a RFC 822 message into a program and have
: it return the return address.  The Reply-To: line should take
: precedence (sp?) over the From: line.  I'm using a UNIX box
: with System V.  A shell script or C program would be nice.
: I don't use perl, but I guess I could learn.

Here's the usual Perl incantation for such things.  It relies on two
subtle tricks: first, if you split a string using a pattern with
parens, it returns the corresponding portions of the delimiters as well
as the fields between delimiters, and second, if you assign a list to
an associative array, each pair of strings becomes one key-value pair.
Once you've done that you can look at the entries in any order you please.

    #!/usr/bin/perl
    $/ = "";					# paragraph mode
    $* = 1;					# multi-line pattern matching
    $_ = <>;					# read one paragraph
    %head = ('PRESTUFF', split(/^(\S+):\s*/));	# split on entry names
    print $head{'Reply-To'} || $head{'From'};	# print the one you want

You can even get at the uucp-style colon-less From line if you so desire
since that will be part of PRESTUFF, if the article contains such a line.

Also, if you're allergic to answers with embedded newlines, you can say

    s/\n[ \t]+/ /g;				# join multi-line entries

just before the split line.

Larry Wall
lwall@netlabs.com