Re: Basic ps Tips

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Sujet : Re: Basic ps Tips
De : mail (at) *nospam* rkta.de (Rene Kita)
Groupes : comp.unix.shell
Date : 04. Aug 2024, 07:56:36
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <v8n8n4$3ugbk$1@dont-email.me>
References : 1 2 3 4 5 6 7
User-Agent : tin/2.6.2-20221225 ("Pittyvaich") (OpenBSD/7.5 (amd64))
Joerg Mertens <joerg-mertens@t-online.de> wrote:
Rene Kita <mail@rkta.de> wrote:
Ed Morton <mortonspam@gmail.com> wrote:
On 8/3/2024 2:08 AM, Rene Kita wrote:
Jerry Peters <jerry@example.invalid> wrote:
Lawrence D'Oliveiro <ldo@nz.invalid> wrote:
On Sat, 27 Jul 2024 00:40:49 -0000 (UTC), I wrote:
[...]
     ps -p$(pgrep -d, bash) -wwo pid,ppid,lstart,tty,etime,cmd
>
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.
 
I'm pretty sure I know which version of BSD I'm running and I would be
very surprised if OpenBSD would ship the FreeBSD version of ps...
 
But let's have a look at the source:
#v+
        while ((ch = getopt(argc, argv,
            "AaCcefgHhjkLlM:mN:O:o:p:rSTt:U:uvW:wx")) != -1)
                switch (ch) {
                case 'A':
                        all = 1;
                        xflg = 1;
                        break;
                case 'a':
                        all = 1;
                        break;
                case 'C':
                        break;                  /* no-op */
#v-
 
'-C' does nothing. I did not look further to see where that error is
coming from.
 
The error message also is printed, when you run ps with a valid
flag plus some string, like `ps -a xyz´, so it seems to be independent
of the `-C´-option.  Maybe it has to do with parsing of the old-style
flags vs. the dashed ones.

You got me curious and I got my debugger out for my morning coffee.

The error message comes from a function kvm_openfiles, which is called
after the flag parsing is done. From a quick glance, this function takes
what looks like three file names. If the second one is NULL, it will
default to /dev/mem. Trying to open /dev/mem it will error out - which
could be due to me being on a VPS.

While the man page mentions kvm(3) in the SEE ALSO section, there is no
mentioning nor explanation what additional arguments can be passed to
ps.

Regards

Date Sujet#  Auteur
27 Jul 24 * Basic ps Tips22Lawrence D'Oliveiro
30 Jul 24 `* Re: Basic ps Tips21Lawrence D'Oliveiro
2 Aug 24  `* Re: Basic ps Tips20Jerry Peters
2 Aug 24   +- Re: Basic ps Tips1Lawrence D'Oliveiro
3 Aug 24   `* Re: Basic ps Tips18Rene Kita
3 Aug 24    +* Re: Basic ps Tips14Ed Morton
3 Aug 24    i`* Re: Basic ps Tips13Rene Kita
3 Aug 24    i +* Re: Basic ps Tips10Joerg Mertens
4 Aug 24    i i+* Re: Basic ps Tips7Rene Kita
4 Aug 24    i ii`* Re: Basic ps Tips6Joerg Mertens
5 Aug 24    i ii +* Re: Basic ps Tips4Lawrence D'Oliveiro
5 Aug 24    i ii i+* Re: Basic ps Tips2Joerg Mertens
5 Aug 24    i ii ii`- The whole point of the BSDs is to be retro (Was: Basic ps Tips)1Kenny McCormack
5 Aug 24    i ii i`- Re: Basic ps Tips1Christian Weisgerber
5 Aug 24    i ii `- Re: Basic ps Tips1Rene Kita
4 Aug 24    i i`* Re: Basic ps Tips2Christian Weisgerber
5 Aug 24    i i `- Re: Basic ps Tips1Rene Kita
3 Aug 24    i `* Re: Basic ps Tips2Lawrence D'Oliveiro
4 Aug 24    i  `- Re: Basic ps Tips1John D Groenveld
4 Aug 24    `* Re: Basic ps Tips3Christian Weisgerber
4 Aug 24     `* Re: Basic ps Tips2Christian Weisgerber
5 Aug 24      `- Re: Basic ps Tips1Lawrence D'Oliveiro

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