Re^2: system function is returning status -1 when running a unix command

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.

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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]