How to Determine Whether a Process Is Running or Not and Make Use It to Make a Conditional Shell Script?

Question

How can I determine if a process is running or not and then have a bash script execute some stuff based on that condition?

For example:

if process abc is running, do this
if it is not running, do that.

Accepted Answer

A bash script to do something like that would look something like this:

#!/bin/bash

# Check if gedit is running
# -x flag only match processes whose name (or command line if -f is
# specified) exactly match the pattern. 

if pgrep -x "gedit" > /dev/null
then
    echo "Running"
else
    echo "Stopped"
fi

This script is just checking to see if the program "gedit" is running.

Or you can only check if the program is not running like this:

if ! pgrep -x "gedit" > /dev/null
then
    echo "Stopped"
fi

Answer 2

Any solution that uses something like ps aux | grep abc or pgrep abc are flawed.

Must Read

Why?

Because you are not checking if a specific process is running, you are checking if there are any processes running that happens to match abc. Any user can easily create and run an executable named abc (or that contains abc somewhere in its name or arguments), causing a false positive for your test. There are various options you can apply to ps, grep and pgrep to narrow the search, but you still won't get a reliable test.

How to Determine Whether a Process Is Running or Not and Make Use It to Make a Conditional Shell Script?

13 Answers

Must Read

Why?

David Miller