topic Re: PID with pipe command in Operating System - HP-UX

PID with pipe command

Siva_13 — Thu, 04 Nov 2004 12:16:27 GMT

Hi,

We are running a command and piping the output to 'tee'

cmd | tee -a sample.log &
print "$!" > pid_file

Since we are using the pipe, the PPID is getting stored in the pid_file.

Could anyone tell us how to get the PID in the pid_file.

The PID stored in the pid_file will be later used for killing the 'cmd' using a
'stop script'.

Could anyone tell how we can get this functionality?

Thanks,
Siva

Re: PID with pipe command

Mark Greene_1 — Thu, 04 Nov 2004 12:30:18 GMT

Unless the "cmd" is really a shell script, you cannot, it's a timing issue. Your best bet is to change the print $$ to a ps -ef |grep cmd|grep -v grep|tr -s " " |cut -d" " -f3>pdi_file to extract the PID from the ps listing.

mark

Re: PID with pipe command

Hein van den Heuvel — Thu, 04 Nov 2004 12:42:52 GMT

$ perl -e 'sleep 1000; print "done\n"' | tee -a x.x &
[1] 15219
$ print $!
15219
$ ps -f
UID PID PPID C STIME TTY TIME COMMAND
root 15219 4146 0 07:29:04 pts/0 0:00 tee -a x.x
root 15220 15219 0 07:29:04 pts/0 0:00 perl -e sleep 1000; print "done\n"
root 15221 4146 1 07:29:17 pts/0 0:00 ps -f
root 4146 4138 0 Nov 2 pts/0 0:00 -sh

$ ps -f | awk -v pid=$! '{ if ($3==pid){print $2}}'
15220

hth,
Hein.

Re: PID with pipe command

Fred Ruffet — Thu, 04 Nov 2004 12:44:25 GMT

You can do it using perl :

perl -e 'if (!($pid=fork())) { exec("sleep 30") } print "$pid\n";' | read childPID

this will return pid of subprocess in childPID env var. Note that this is really basic code, and you may need to enhance fork management, redirect STDIN and STDOUT for complete separation...

Regards,

Fred

Re: PID with pipe command

Fred Ruffet — Thu, 04 Nov 2004 12:47:19 GMT

I forgot the proof / sample (I tested and it worked :)

#perl -e 'if (!($pid=fork())) { exec("sleep 30") } print "$pid\n";' | read childPID
#echo $childPID
27507
#ps
PID TTY TIME COMMAND
27094 pts/tb 0:00 sh
27507 pts/tb 0:00 sleep
27093 pts/tb 0:00 telnetd
27508 pts/tb 0:00 ps

Regards,

Fred