How do I check whether `lwp-download` worked correctly?

Question

Hey.

I don't know anything about Perl but I urgently need to modify a Perl script. At some point it's downloading an about 500MB file from a server using system("lwp-download $HttpPath $Out");.

Is there any way I can find out if the downloading process went correctly, e.g. check whether downloaded file has the same size as the original one?

Thanks

Answer 1

In general, the system command returns^* the exit status of the program that it was running. By convention a return value of zero means success, and non-zero means some sort of error.

A typical idiom is something like

my $status = system($command);
if ($status == 0) {
    # the program succeeded ...
} else {
    # the program failed ...
    warn "The program failed. Status = ", $status>>8, "\n";
}

^* - sort of, see perldoc -f system for details

Answer 2

It's a dumb thing to shell out from your Perl program to run lwp-download, another Perl program. Just replace that call with the mirror API from LWP::Simple and you get decent error reporting, directly there in your program instead of messing with exit codes.

Should you need even better/fine-grained error checking, mirror from LWP::UserAgent is available, too.