How can I redirect the output of Perl's system() to a filehandle?

Question

With the open command in Perl, you can use a filehandle. However I have trouble getting back the exit code with the open command in Perl.

With the system command in Perl, I can get back the exit code of the program I'm running. However I want to just redirect the STDOUT to some filehandle (no stderr).

My stdout is going to be a line-by-line output of key-value pairs that I want to insert into a mao in perl. That is why I want to redirect only my stdout from my Java program in perl. Is that possible?

Note: If I get errors, the errors get printed to stderr. One possibility is to check if anything gets printed to stderr so that I can quite the Perl script.

Answer 1

Canonically, if you're trying to get at the text output of a forked process, my understanding is that's what the backticks are for. If you need the exit status as well, you can check it with the $? special variable afterward, e.g.:

open my $fh, '>', "output.txt" or die $!;
print {$fh} `echo "Hello!"`;
print "Return code: $?\n";

Output to STDERR from the command in backticks will not be captured, but will instead be written directly to STDERR in the Perl program it's called from.

Answer 2

You may want to check out IPC::System::Simple -- it gives you many options for executing external commands, capturing its output and return value, and optionally dying if a bad result is returned.