topic Re: run command concurrently within script in Operating System - HP-UX

run command concurrently within script

yc_2 — Tue, 31 Mar 2009 06:31:34 GMT

Hi,

Is it possible to write a script to run multiple commands concurrently? Example: perform fsck for a few file systems.

Thanks in advance

Re: run command concurrently within script

Steven E. Protter — Tue, 31 Mar 2009 06:39:56 GMT

Shalom,

Yes

#!/bin/ksh

command1 &
command2 &
command3 &

Doing this with fsck might cause I/O to go high, but it should work.

SEP

Re: run command concurrently within script

yc_2 — Tue, 31 Mar 2009 07:20:09 GMT

Any way to capture the output since it is in back ground?

Re: run command concurrently within script

Torsten. — Tue, 31 Mar 2009 07:24:37 GMT

Try

# command1 >/tmp/command1.out 2>/tmp/command1.out &

BTW, fsck on a newly created filesystem is maybe not needed and will return very quickly.

Re: run command concurrently within script

yc_2 — Tue, 31 Mar 2009 08:09:29 GMT

Thanks. I will try it out. The fsck is use for true copy purpose.

Re: run command concurrently within script

yc_2 — Tue, 31 Mar 2009 08:12:17 GMT

Why pipe 2 times to the same file?

# command1 >/tmp/command1.out 2>/tmp/command1.out &

Re: run command concurrently within script

Torsten. — Tue, 31 Mar 2009 08:18:21 GMT

One ">" was missing, sorry.

# command1 >/tmp/command1.out 2>>/tmp/command1.out &

But you can use different files, of course.

Re: run command concurrently within script

Bill Hassell — Tue, 31 Mar 2009 11:01:18 GMT

> # command1 >/tmp/command1.out 2>>/tmp/command1.out &

This is a better way if all output (stdout and stderr must go into the same file):

cmd1 > /tmp/cmd1.log 2>&1 &
cmd2 > /tmp/cmd2.log 2>&1 &

The construct 2>&1 says: take stderr (file number 2) and redirect it into file number 1. Each time the command runs, it will clear the log file. To track all runs of the command, change > to >> as in:

cmd1 >> /tmp/cmd1.log 2>&1 &
cmd2 >> /tmp/cmd2.log 2>&1 &

For cumulative logs, be sure to add a timestamp, especially one that can be easily sorted or selected such as YYYYMMDD.HHMMSS. You can add this to your scripts:

echo "$(date +%Y%m%d.%H%M%S) and sime text..."

Or for applications that you can't modify, add the timestamp before running the program:

echo "$(date +%Y%m%d.%H%M%S)" >> cmd1.log; cmd1 >> /tmp/cmd1.log 2>&1 &
echo "$(date +%Y%m%d.%H%M%S)" >> cmd1.log; cmd2 >> /tmp/cmd2.log 2>&1 &