HP-UX $ ps -eo pid,ppid,comm
ps: illegal option -- o
usage: ps [-edaxzflP] [-u ulist] [-g glist] [-p plist] [-t tlist] [-R prmgroup] [-Z psetidlist]

AIX $ ps -eo pid,ppid,comm
   PID   PPID COMMAND
     1      0 init
 78030 143498 xntpd
:

NetBSD $ ps -eo pid,ppid,comm
  PID  PPID COMMAND
 5908 16576 USER=tux LOGNAME=tux HOME=/home/tux PATH=/usr/bin:/bin:/usr/pkg/bin:/u
22789  5908 USER=tux LOGNAME=tux HOME=/home/tux PATH=/home/tux/bin:/usr/local/bin:

Windows C:\Users\Tux>ps -eo pid,ppid,comm
'ps' is not recognized as an internal or external command,
operable program or batch file.