User1
2010-07-27 17:00:10
why are you killing a process whose output you want?
msw
2010-07-27 17:08:26
The process is a hardware monitoring program that will run until it is killed. When the process receives the kill signal, it flushes its buffer. In reality, the bash script will kill my_prog when the test is over which is represented by the sleep statement above.
User1
2010-07-27 17:13:57
+2
A:
Based on your comment, I still can't see why you'd prefer killing my_prog to having it complete in an orderly fashion. Ten seconds is a pretty arbitrary measurement on a multiprocessing system whereby my_prog could generate 10k lines or 0 lines of output depending upon system load.
If you want to limit the output of my_prog to something more determinate try
my_prog | head -1000 | awk
without detaching from the shell. In the worst case, head will close its input and my_prog will get a SIGPIPE. In the best case, change my_prog so it gives you the amount of output you want.
added in response to comment:
In so far as you have control over my_prog give it an optional -s duration argument. Then somewhere in your main loop you can put the predicate:
if (duration_exceeded()) {
exit(0);
}
where exit will in turn properly flush the output FILEs. If desperate and there is no place to put the predicate, this could be implemented using alarm(3), which I am intentionally not showing because it is bad.
The core of your trouble is that my_prog runs forever. Everything else here is a hack to get around that limitation.
msw
2010-07-27 17:02:18
See my comment in my answer. I guess I could have given more detail on the original question. The solution above might work for some, but this case is a bit different. Thank you for all your help so far. I hope you can tell me of an easier solution than my answer.
User1
2010-07-27 17:18:38
+2
A:
Add a shell wrapper around your command and capture the pid. For my example I use iostat.
#!/bin/sh
echo $$ > /tmp/my.pid
exec iostat 1
Exec replaces the shell with the new process preserving the pid.
test.sh | grep avg
While that runs:
$ cat my.pid
22754
$ ps -ef | grep iostat
userid 22754 4058 0 12:33 pts/12 00:00:00 iostat 1
So you can:
sleep 10
kill `cat my.pid`
Is that more elegant?
Demosthenex
2010-07-27 17:38:12