Re: system function is returning status -1 when running a unix command

Sounds like your DB stuff is messing with SIGCHLD.

$ perl -wle'$SIG{CHLD}="IGNORE"; print system("ls -d ."); print $!'
.
-1
No child processes
[download]

system is basically fork + exec (in the child) + waitpid (in the parent). In the above example, children are auto-reaped, so system has no child to wait for, so it returns an error.

strace (or truss or whatever it's called on Solaris) would confirm this diagnosis.

Update: Added last line.

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Re^2: system function is returning status -1 when running a unix command by repellent (Priest) on Apr 08, 2009 at 18:16 UTC
ikegami, could you please explain what is going on here: `> perl -wle ' $SIG{CHLD}="IGNORE"; $! = 33; print system("ls -d ."); print -+-$!; print $!; print -+-$!' . -1 33 No child processes 10` [download] It seems that string-ifying `"$!"` changes its value.	[reply] [d/l] [select]
Re^3: system function is returning status -1 when running a unix command by ikegami (Patriarch) on Apr 08, 2009 at 18:37 UTC
`print` can result in system calls. `$!` is meaningless after the first `print`. `$ perl -wle' $SIG{CHLD}="IGNORE"; $! = 0; my $rv = system("ls -d ."); my $errno = $!; print $rv; print 0+$errno; print $errno; print 0+$errno; ' . -1 10 No child processes 10` [download] Note that `0+` is much easier to understand than `-+-`, and it conveys the intent much better.	[reply] [d/l] [select]