Why can't I pgrep a process?

Question

$ ps aux | grep -i ssh
USER      4364  0.0  0.0   9004  1032 ?        Ss   12:20   0:00 ssh -v -fND localhost:4000 USERNAME@SERVER-IP-ADDRESS

$ pgrep localhost:4000

Why doesn't this work?

score 25 · Accepted Answer · answered May 17 '11 at 11:00

25

By default, pgrep(1) will only match against the process name. If you want to match against the full command line, use the -f option:

$ pgrep -f localhost:4000

answered May 17 '11 at 11:00

camh

39,069

To understand why this happens, look at https://unix.stackexchange.com/a/267021/249938 – subtleseeker Oct 15 '20 at 08:16

score 8 · Answer 2 · answered May 17 '11 at 11:01

Have a look at the man page for pgrep. It is not just an alias for running ps with a bunch of columns and then greping the text output. It actually searches specific fields for values. By default, it only looks at the process name when doing a search and returns the PID. You can search the full command line by adding the -f option. You can also search several other fields that might be useful such as matching the terminal where a process is running or the group id.

Why can't I pgrep a process?

2 Answers2