Re: Basic ps Tips

On 8/3/2024 2:08 AM, Rene Kita wrote:

Jerry Peters <jerry@example.invalid> wrote:

Lawrence D'Oliveiro <ldo@nz.invalid> wrote:

On Sat, 27 Jul 2024 00:40:49 -0000 (UTC), I wrote:

[...]

     ps -p$(pgrep -d, bash) -wwo pid,ppid,lstart,tty,etime,cmd
>
to report all the bash sessions I have running (quite a lot). The ???ww???
says not to truncate the output, which is handy for long command lines.

  Or just use ps -C <command>:

[...]

Does noone know about -C? I keep seeing things like 'ps -ef | grep
<something> in scripts to see if <something is running, rather than
using 'ps -C'.

 I did not know about it.
 The man page on OpenBSD does not mention -C, but calling 'ps -C' does
not give an error. But:
#v+
$ ps -C ksh
ps: /dev/mem: Permission denied'
#v-
 Dunno what to make out of it, but apparently one reason to use grep
instead of -C is portability.

Its described in the man page for FreeBSD ps, https://man.freebsd.org/cgi/man.cgi?ps(1), as:
        -C      Change  the  way the  CPU  percentage is calculated by using a
       "raw" CPU calculation that ignores "resident" time  (this  nor-
       mally has no effect).
so maybe you're running FreeBSD instead of the OpenBSD version.
Using `-C` to select a command isn't supported by POSIX, GNU, FreeBSD, OpenBSD, etc. so yes - portability would be a significant issue if you relied on it in your scripts.
     Ed.

 

         Jerry

Rene