ps -c num bug or feature ?

[Hans Buurman]

I don't understand the following behaviour of ps (SunOs 4.0.1):

hans52> ps
  PID TT STAT  TIME COMMAND
23706 p0 S     0:03 -csh (csh)
23728 p0 R     0:00 ps
hans53> ps -c
  PID TT STAT  TIME COMMAND
23706 p0 S     0:03 csh
23731 p0 R     0:00 ps
hans54> ps 23706
  PID TT STAT  TIME COMMAND
23706 p0 S     0:03 -csh (csh)
hans55> ps -c 23706
ps: cannot open 23706: No such file or directory

This should be correct according to the manual, I think.
>From the SunOS manual:

     num  A process number may be given, in which case the output
          is  restricted  to that process.  This option must also
          be last.


It happens with other options as well.
Can anybody tell me whether this is a bug or a feature ?

	Hans

(willing to summarise)
========================================================================
Hans Buurman               | hans at duttnph.tudelft.nl | hans at duttnph.UUCP
Pattern Recognition Group  | 31-(0)15-78 46 94       |
Faculty of Applied Physics | Delft University of Technology