Get Information with scan Format Strings

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The Section MH Format Strings showed how to write format files for scan. Format files, or format strings, are a great way to get information about mail messages for a shell program. For instance, here's a a format string that prints the message number in a field of width 4, a space, then either the Sender: (if the message has one) or the From:. It formats the addresses with the %(friendly) function, which gives a "nice" output when it can.

$ scan -format "%4(msg) %<{sender}%(friendly{sender})%|%(friendly{from})%>"
  46 "Don C. Meach"
  47 mh-users-request@ics.uci.edu
  48 Jerry Peek
You could use a scan format string like that to write a simple loop that processes mail messages automatically. The loop below uses the (mbox) function to get the address without the hostname. (There are more efficient ways to process incoming mail -- see the Chapter Processing New Mail Automatically.)
msgfrom="%(msg) %<{sender}%(mbox{sender})%|%(mbox{from})%>"
    ...
scan -format "$msgfrom" |
while read msgnum from
do
    # DON'T READ ANYTHING FROM steveq; refile ALL mh-users MAIL.
    # LEAVE OTHER MESSAGES ALONE:
    case "$from" in
    steveq) rmm $msgnum ;;
    mh-users) refile $msgnum +mh-users ;;
    esac
done
This is using a Bourne shell while loop with its standard input taken from the pipe (from the scan command). The read command reads a line of input; it puts the first word (here, the message number) in a shell variable named msgnum, and the rest (the local part of the address) goes into the variable called from. Then, a case structure checks who sent the message and does the right thing with it.

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Last change $Date: 1996/06/06 15:14:48 $

This file is from the third edition of the book MH & xmh: Email for Users & Programmers, ISBN 1-56592-093-7, by Jerry Peek. Copyright 1991, 1992, 1995 by O'Reilly & Associates, Inc. This file is freely-available; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation. For more information, see the file copying.htm.

Suggestions are welcome: Jerry Peek <jerry@ora.com>

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Last modified: Friday April 02, 1999.