Linux/Unix command to determine if process is running?

Question

I need a platform independent (Linux/Unix|OSX) shell/bash command that will determine if a specific process is running. e.g. mysqld, httpd... What

Answer 1

Putting the various suggestions together, the cleanest version I was able to come up with (without unreliable grep which triggers parts of words) is:

kill -0 $(pidof mysql) 2> /dev/null || echo "Mysql ain't runnin' message/actions"

kill -0 doesn't kill the process but checks if it exists and then returns true, if you don't have pidof on your system, store the pid when you launch the process:

$ mysql &
$ echo $! > pid_stored

then in the script:

kill -0 $(cat pid_stored) 2> /dev/null || echo "Mysql ain't runnin' message/actions"

Answer 2

This approach can be used in case commands 'ps', 'pidof' and rest are not available. I personally use procfs very frequently in my tools/scripts/programs.

   egrep -m1  "mysqld$|httpd$" /proc/[0-9]*/status | cut -d'/' -f3

Little explanation what is going on:

1. -m1 - stop process on first match
2. "mysqld$|httpd$" - grep will match lines which ended on mysqld OR httpd
3. /proc/[0-9]* - bash will match line which started with any number
4. cut - just split the output by delimiter '/' and extract field 3