Why does "ps aux | grep x" give better results than "pgrep x"?
The ps aux | grep x
command gives "better" results than pgrep x
essentially because you are missing an option with the latter.
Simply use the -f
option for pgrep
to search the full command line and not only the process name which is its default behavior, eg:
pgrep -f php5
Unlike the ps | grep
construction with which you need to filter out the grep
line or use pattern tricks, pgrep
just won't pick itself by design.
Moreover, should your pattern appear in ps
USER
column, you'll get unwanted processes in the output, pgrep
doesn't suffer from this flaw.
If you want full details instead of just the pids, you can use:
ps wup $(pgrep -f python)
which is simpler and more reliable than
ps aux | grep python | grep -v grep
or
ps aux | grep p[y]thon
ps aux
includes the full command line (path and parameters), while pgrep only looks at the first 15 characters of the executable's names
ps aux
returns the full command line of each process, while pgrep
only looks at the names of the executables.
That means that grepping ps aux
output will match anything that occurs in the path or the parameters of a process' binary: e.g. `
ps aux | grep php5
will match/usr/share/php5/i-am-a-perl-script.pl
- but
pgrep php5
won't
Take an example from my system -- only we'll use python instead of php5
:
ps aux | grep python
gives us:
izx 2348 0.0 0.7 514928 15644 ? Sl Jun24 0:00 /usr/bin/python /usr/lib/unity-lens-video/unity-lens-video izx 2444 0.0 0.9 547392 18864 ? Sl Jun24 0:01 /usr/bin/python /usr/lib/unity-scope-video-remote/unity-scope-video-remote root 2805 0.0 0.5 95436 12204 ? S Jun24 0:00 /usr/bin/python /usr/lib/system-service/system-service-d izx 6272 0.0 2.9 664400 60320 ? SNl Jun24 1:16 /usr/bin/python /usr/bin/update-manager --no-focus-on-map root 11729 0.0 0.9 180508 19516 ? S Jun25 0:00 python /usr/lib/software-properties/software-properties-dbus
- But
pgrep python
returns only11729
, which you'll see from the above list is:
root 11729 0.0 0.9 180508 19516 ? S Jun25 0:00 python /usr/lib/software-properties/software-properties-dbus
diff <(ps aux|grep x) <(pgrep x) # :)