Consider using pgrep instead of grepping ps output SH-2009

If you are just after a pid from a running program, then pgrep is a much safer alternative. Especially if you are also looking for a pid belonging to a certain user or group. pgrep rolls a number of functionalities into one and can eliminate multiple greps, cuts, seds and awks.

If you want a field that's not the pid, consider doing this through ps + pgrep instead of ps + grep:

for pid in $(pgrep '^python$')
do
  user=$(ps -o user= -p "$pid")
  echo "The process $pid is run by $user"
done

This is more robust than ps .. | grep python | cut .. because it does not try to match against unrelated fields, such as if the user's name was pythonguru.

Problematic code:

ps ax | grep -v grep | grep "$service" > /dev/null

Preferred code:

pgrep -f "$service" > /dev/null

Exception:

You can ignore this issue if you are trying to match against something that pgrep doesn't support.