>From a Linux man page on sigaction ...

       POSIX (B.3.3.1.3) disallows setting the action for SIGCHLD
       to  SIG_IGN.   The BSD and SYSV behaviours differ, causing
       BSD software that sets the action for SIGCHLD  to  SIG_IGN
       to fail on Linux.

And from another Linux man page (for wait()) I found.

NOTES
       The  Single  Unix Specification describes a flag SA_NOCLD-
       WAIT (not present under Linux) such that  if  either  this
       flag  is  set, or the action for SIGCHLD is set to SIG_IGN
       (which, by the way, is not allowed by POSIX),  then  chil-
       dren  that exit do not become zombies and a call to wait()
       or waitpid() will block until all  children  have  exited,
       and then fail with errno set to ECHILD.

What fun!

And I'm sure SIG_IGN for BSD doesn't stop the need for waiting on
the child.

--Phil

-- 
Phil Nelson                       NetBSD: http://www.netbsd.org
e-mail: phil@cs.wwu.edu           Coda: http://www.coda.cs.cmu.edu
http://cs.wwu.edu/faculty/nelson