GNU Parallel Bug Reports Bug with version 20120322: --timeout gives ps error

[parallel]

Failing command:
# parallel -S : --nonall --timeout 1 sleep 2
ps: illegal option -- -
usage: ps [-AaCcEefhjlMmrSTvwXx] [-O fmt | -o fmt] [-G gid[,gid...]]
          [-g grp[,grp...]] [-u [uid,uid...]]
          [-p pid[,pid...]] [-t tty[,tty...]] [-U user[,user...]]
       ps [-L]

As the comment in the source indicates, this needs to be tested with
other operating systems.

For MacOSX 10.6.8, the correct ps command is: 
  ps -o ppid= -p $$
Note, there is nothing after the equal sign; this deletes the header.