pgrepinstead of grepping
ps ax | grep -v grep | grep "$service" > /dev/null
pgrep -f "$service" > /dev/null
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. All of the parameters are in one command and it can eliminate multiple greps, cuts, seds, awks, etc.
If you want a field that's not the pid, consider doing this through
pgrep instead of
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
pgrep is not POSIX. Please ignore this warning if you are targeting POSIX userlands.
You can ignore this error if you are trying to match against something that
pgrep doesn't support:
# pgrep does not support filtering by 'nice' value # shellcheck disable=SC2009 ps -axo nice=,pid= | grep -v '^ 0'
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