tree 0c0b2b75cfcf364198e451143344995a9a3abd60
parent 45e0acc110465175afc678ee103f2f5c4e6b270f
author Elliott Hughes <enh@google.com> 1446321697 -0700
committer Rob Landley <rob@landley.net> 1446449975 -0600

Make ps -o error reporting intelligible.

I actually thought ps was segfaulting, and it wasn't until I was in gdb
that I even noticed there was an error message at all, and even then I
had to read the source to work out what it was trying to tell me.

Before:
  $ ps -o user,pid,ppid,vsize,rss,nice,wchan,addr,unknown,stat,cmd
  ps: -o 'user,pid,ppid,vsize,rss,nice,wchan,addr,unknown,stat,cmd'@41
  USER       PID  PPID    VSZ   RSS  NI WCHAN          ADDR$

After:
  $ ps -o user,pid,ppid,vsize,rss,nice,wchan,addr,unknown,stat,cmd
  ps: bad -o field 'user,pid,ppid,vsize,rss,nice,wchan,addr,unknown,stat,cmd'
                                                            ^