Re: Basic ps Tips

On 2024-08-03, Joerg Mertens <joerg-mertens@t-online.de> wrote:

[OpenBSD ps(1)]

$ ps -C ksh
ps: /dev/mem: Permission denied'

>
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.

A quick look at the options parsing shows that

  ps xxx [yyy [zzz]]

is equivalent to

  ps -N xxx [-M yyy [-W zzz]]

This has been unchanged since the initial fork from NetBSD in 1995.
Digging further, I see that this comes straight from 4.4BSD, and
that the -M, -N, -W flags were added in 1991 and the older argument
syntax was left in place for backward compatibility.

FreeBSD changed this twenty years ago and now treats additional
arguments as a list of PIDs.

A further complication, going back to 4.4BSD, is that the arguments
are run through a function kludge_oldps_options() before actual
argument parsing, again for backward compatibility:

  ps foo -> ps -foo
  ps 34 -> ps -p34

--
Christian "naddy" Weisgerber                          naddy@mips.inka.de