in reply to What is a successful return status for perl wait() in Solaris?

Only one byte is allowed for a return status on UNIX, so 255, 0xff, all bits set is the max allowed. Setting 256 potentially sets a bit in the more significant byte, leaving the status byte as zero.
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Re^2: What is a successful return status for perl wait() in Solaris?
by kduong (Initiate) on Feb 01, 2008 at 15:53 UTC
    Thanks for the information. So does 256 exit status means a successful exit of the child process? What happened is there is a bug in one of our program and the program will abort if $? >> 8 == 0. I can see if I terminate a child process, the exit status of wait is 0. But I thought the exit status of 0 means success, that's why I am a little bit confused.
[reply]
      So does 256 exit status means a successful exit of the child process?
      No, you cannot exit with 256 from UNIX, only 0-255. However, if you are talking about $?, that is a different matter. As others have said, $? contains many things other than just the return code. If the child process terminated because of a signal then the signal number is in $? as well.
      $exit_value    = $? >> 8; 
$signal_num    = $? & 127;
$dumped_core    = $? & 128;

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      I think there has been some confusion over what you mean by an exit value.
[reply]
[d/l]
        Does that mean waitpid() for a process id $pid forked by a fork command can expect a return code ( $? ) more than 255. I believe waitpid() should expect $? to be any value between 0-255 ( i. e. the child process (with $pid ) should always exit with a value between 0-255. ) Please clarify my doubt.
[reply]
        So does exit value 256 means a successful exit?
[reply]

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