Call a jar using perl and pass variables using STDIN

Question

I am calling a jar via perl with the following command.

my $command = "$java_home/bin/java my_jar.jar ARG1 ARG2 ARG3";
my $result = `$command 2>&1;

However my JAR also expects arguments via STDIN. I need to know how to pass those arguments. I have tried passing them like normal arguments, and that didn't work. I read on a forum that OPEN2 might work however after reading the documentation I couldn't figure out how to make it work.

Any ideas on how to make this work would be great.

Thanks ahead of time.

Answer 1

Since you need to send and receive data from the Java process, you need two-way communication. That's what IPC::Open2 is designed to do. This allows you to create a dedicated pipe that renders STDIN/STDOUT unnecessary:

use IPC::Open2;

my $pid = open2( \*from_jar, \*to_jar, $command )
            or die "Could not open 2-way pipe: $!";

print to_jar, "Here is input\n";  # Pass in data

my $result = <from_jar>;          # Retrieve results

Also consider IPC::Open3 to handle errors as well.