Finding Out Whether a Process Is Running
Problem
You need to determine whether a process is running, and you might or might not already have a process ID (PID).
Solution
If you don’t already have a PID, grep the
output of the ps command to see if the program you
are looking for is running. See Grepping ps Output Without Also Getting the grep Process
Itself,
for details on why our pattern is [s]sh
.
$ [ "$(ps -ef | grep 'bin/[s]shd')" ] && echo 'ssh is running' || echo 'ssh not running'
That’s nice, but you know it’s not going to be that easy, right? Right. It’s difficult because ps can be wildly different from system to system.
# cookbook filename: is_process_running # Can you believe this?!? case `uname` in Linux|AIX) PS_ARGS='-ewwo pid,args' ;; SunOS) PS_ARGS='-eo pid,args' ;; *BSD) PS_ARGS='axwwo pid,args' ;; Darwin) PS_ARGS='Awwo pid,command' ;; esac if ps $PS_ARGS | grep -q 'bin/[s]shd'; then echo 'sshd is running' else echo 'sshd not running' fi
If you do have a PID, say from a lock file or an environment
variable, just search for it. Be careful to match the PID up with some
other recognizable string so that you don’t have a collision where some
other random process just happens to have the stale PID you are using.
Just obtain the PID and use it in the grep or in a
-p
argument to
ps:
# Linux $ ps -wwo pid,args -p 1394 | grep 'bin/sshd' 1394 /usr/sbin/sshd # BSD $ ps ww -p 366 | grep 'bin/sshd' 366 ?? Is 0:00.76 /usr/sbin/sshd
Discussion
The test and grep portion of the solution requires ...
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