capturing line from script output and appending to a file

wally_welder · #1 (**permalink**) 08-30-2007

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)

Code:

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

This generates output exactly as shown:
[many preceding lines of exactly the same format]
postsuper: E657736C82BD: removed
postsuper: E1CAD36C8074: removed

and finally, at the end of the output:
postsuper: Deleted: 127 messages

What I'm trying to figure out how to do is this.....
Grab the number of deleted messages, and append them to a file with a timestamp e.g. 20070830 07:32 - 127

so somewhere in the latter end of this would be >> cron_purges

Can anyone help me understand how to grab *just* the number, and hang a timestamp onto it as shown in the above example?

Regards & TIA!
Wally

ranj@chn · #2 (**permalink**) 08-30-2007

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.

Code:

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

Format the date to get the date-time stamp required

Code:

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

Now echo this to a file where you want to log this.

Code:

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

wally_welder · #3 (**permalink**) 08-30-2007

Quote:

Originally Posted by ranj@chn

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.

Code:

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

Format the date to get the date-time stamp required

Code:

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

Now echo this to a file where you want to log this.

Code:

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

ranj@chn · #4 (**permalink**) 08-30-2007

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.

Code:

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

The rest being the same. Remove the tempfile afer the work is over. If this is not working, then do check if the last line is a blank line in the tempfile. Empty lines at the end could also distort the o/p. But I donot know how postsuper works to clearly identify the cause. Hope that helps!!

fazliturk · #5 (**permalink**) 08-30-2007

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

ranj@chn · #6 (**permalink**) 08-31-2007

Quote:

fazliturk
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,

Code:

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

ghostdog74 · #7 (**permalink**) 08-31-2007

Code:

mailq | awk '!/^[^0-9A-Z]+/ && /MAILER-DAEMON/{
     cmd = "postsuper -d " $1
     cmd | getline #or system(cmd)
     close(cmd) 
}'

NB: Not tested.

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