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.