Hi all,
I did some searching in this forum but can't find anything that matches the issue I'm bumping heads with.

On a CentOS4/Postfix (and bash everywhere) mail gateway box I run a command periodically to purge the Postfix queue of messages "From:MAILER-DAEMON".

This is the one line'r (courtesy of the Postfix list archives)

mailq | grep -v "^[^0-9A-Z]+" | grep MAILER-DAEMON | awk '{print $1}' | postsuper -d -

One way would be to get pipe the o/p and filter out the last line and get the no of deleted messages from there & assign it to a variable.

no_of_msgs=$(mailq | grep -v "^[^0-9A-Z]+" | grep MAILER-DAEMON | awk '{print $1}' | postsuper -d - | tail -1 | awk '{print $3}')

dt_time=$(date +'%Y%m%d %H:%M')

echo "$dt_time - ${no_of_msgs}" >>cron_purges

That does some rather interesting things:
1. It does run the deletions successfully, but outputs verbosely to screen in the original format
2. It does write a timestamp to the file cron_purges
but
3. Doesn't capture the number (represented as "xxx" below) appearing in the last line of output:
postsuper: Deleted: xxx messages

Unfortunately, I don't know enough about the syntax to mess around with possible alternatives in order to offer a suggestion...so, I'm a bit stumped still.

Regards & Thanks!
-Wally

I am not sure what exactly is the reason, but the o/p of postsuper -d seems to be not piped to tail command. Try this,
Redirect the o/p of postsuper -d to some tempfile. Get the count of messages from the tempfile.

mailq | grep -v "^[^0-9A-Z]+" | grep MAILER-DAEMON | awk '{print $1}' | postsuper -d - >tempfile
no_of_msgs=$(tail -1 tmpfile |awk '{print $3}')

try this;

NumOfMsg=`.....(your orijinal code) ...|grep Deleted |awk '{print $3}' `
I thing tail is not suitable for pipe why pipe sends line by line so for tail -1 every line will be the last line

tail should work. Check this,

rkumar@bdc4reteaix1w: /home/rkumar >ls
bkgdtest         dead.letter      mbox             mypipe           nohup.out        test.pl          unix_forum
cprog            f1.txt           myfile           newone           restart_sshd.sh  testpipe.sh      whsmith
rkumar@bdc4reteaix1w: /home/rkumar >ls | tail -1
whsmith