Perl: After a successful system call, “or die” command still ends script

Question

I am using the following line to make a simple system call which works:

system (\"mkdir -p Purged\") or die \"Failed to mkdir.\" ;

Executin

Answer 1

To add what hasn't been mentioned but what comes with it and can quietly mess things up.

The system's return of 'zero-or-not' only tells whether the command itself executed successfully, by shell or execvp; the 0 does not mean that the command succeeded in what it was doing.

In case of non-zero return you need to unpack $? for more information; see system for how to do this. For one, the command's actual exit code is $? >> 8, what the executed program was designed to communicate at its exit.

Altogether you may want to do something to the effect of

sub run_system {
    my ($cmd, @other_agrs) = @_;             # may do more via @other_args

    my ($cmdref, $sys_ret) = (ref $cmd, 0);  # LIST or scalar invocation?
    if ($cmdref eq 'ARRAY') {
        $sys_ret = system(@$cmd);
    }
    elsif (not $cmdref) {
        $sys_ret = system($cmd);
    }
    else { Carp::carp "Invocation error, got $cmdref" }

    return 1 if $sys_ret == 0;

    # Still here? The rest is error handling.
    Carp::carp "Trouble with 'system($cmd)': $?";
    print "Got exit " . ($? >> 8) . " from $cmd\n";
    return 0;  # or die (but then design changes)
}

This can be done merely as system == 0 or do { ... }; or such right in the code, but this way there's a little library, where we can refine error handling more easily, eventually decide to switch to a module to manage external commands, etc. Also, being a user-level facility now it makes sense that it returns true on success (we aren't changing system's design).

Additionally in this case, mkdir -p is meant to be quiet and it may not say anything when it cannot do its thing, in some cases. This is by design of course, but one should be aware of it.