Check if a process is running using Bash

Question

I am trying to check if a process is running with the code below:

SERVICE=\"./yowsup/yowsup-cli\"
RESULT=`ps aux | grep $SERVICE`

if [ \"${RESULT:-null}\" =         


        

Answer 1

The problem is that grep you call sometimes finds himself in a ps list, so it is good only when you check it interactively:

$ ps -ef | grep bash
...
myaut    19193  2332  0 17:28 pts/11   00:00:00 /bin/bash
myaut    19853 15963  0 19:10 pts/6    00:00:00 grep --color=auto bash

Easiest way to get it is to use pidof. It accepts both full path and executable name:

service="./yowsup/yowsup-cli" # or service="yowsup-cli"
if pidof "$service" >/dev/null; then
    echo "not running"
else
    echo "running"
fi

There is more powerful version of pidof -- pgrep.

---

However, if you start your program from a script, you may save it's PID to a file:

service="./yowsup/yowsup-cli"
pidfile="./yowsup/yowsup-cli.pid"
service &
pid=$!
echo $pid > $pidfile

And then check it with pgrep:

if pgrep -F "$pidfile" >/dev/null; then
    echo "not running"
else
    echo "running"
fi

This is common technique in /etc/init.d start scripts.