Re^2: multi-command sytem call

When you run a process in the background via the shell (with the &), the return value is always zero.

Not so!

system, exec, and fork can all fail and depending on the function, return a non-zero value if the system cannot fork at the time (say, if there is a runaway process running that has forked too many times). Or actually, on failure fork returns undef, exec returns false, and system returns whatever the secondary process returned. Normal programs return 0 on success but are expected to return non-zero values on failure. So system is perfectly capable of returning non-zero values. When that happens, something wrong has happened in the program that system was running.

The return code of the program is in $? >> 8 so check that when it fails.

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Re^3: multi-command sytem call by etcshadow (Priest) on Aug 25, 2004 at 07:26 UTC
Well, I was talking about the return code in the shell (since this was really more of a shell question than a perl question) and quoting the shell documentation. The OP was talking about the return values of the backgrounded processes, which are ignored in terms of computing the exit code of the shell process, and that's all I meant. I probably should have been more precise, though. `------------ :Wq Not an editor command: Wq` [download]	[reply] [d/l]

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Re^3: multi-command sytem call
by etcshadow (Priest) on Aug 25, 2004 at 07:26 UTC

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