```{index} single: errno (Peta::FFI) ``` ```{index} single: Peta::FFI::errno ``` # errno errno as the last C call through Peta::FFI left it. ## Synopsis ```perl my $fd = Peta::FFI::call($libc, "open", "(pi;u32)i", $path, 0x40, 0644); if ($fd < 0) { local $! = Peta::FFI::errno(); die "open $path: $!"; } ``` ## What you get back An integer: the value errno had the moment the C function returned, read before Perl could change it. As in C, it means something only when the function reported a failure. Assigning it to `$!` gives its message.