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Old 01-13-2004, 07:24 PM   #1
mikshaw
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Registered: Dec 2003
Location: Maine, USA
Distribution: Slackware/SuSE/DSL
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Question [script] check for a running process


I'm wondering if there is a more efficient/compatible way to do this:
Code:
if [ -n "$(ps -A | grep root-tail)" ]; then
   echo "root-tail is already running"
else
   root-tail -f -g 120x30+8+8 ${HOME}/log/console,brown,'messages'
fi
It works for me in a bash script, but I understand $(command) does not work in other shells.
I tried
Code:
if [ -n `ps -A | grep root-tail` ]
but it doesn't seem to work.

Thanks for any help.
 
Old 01-13-2004, 08:21 PM   #2
lyle_s
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Registered: Jul 2003
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You're using command substitution, which substitutes the standard output of a command. All you're looking for if the return value of the command.

Code:
if ps -C root-tail > /dev/null; then
	echo "root-tail is already running"
else
	root-tail -f -g 120x30+8+8 ${HOME}/log/console,brown,'messages'
fi
Lyle
 
Old 01-13-2004, 08:33 PM   #3
mikshaw
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Registered: Dec 2003
Location: Maine, USA
Distribution: Slackware/SuSE/DSL
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Hmmm...that looks interesting.
However, ps -C <command> still returns "PID TTY TIME CMD" even if the specified process isn't running, which is why I added the grep.
So maybe if `ps -A | grep root-tail` > /dev/null; would work?


Oh...it seems the "PID TTY TIME CMD" doesn't have any effect, so it works fine.
Thank you

Last edited by mikshaw; 01-13-2004 at 09:14 PM.
 
  


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