Passing variable to Java from Perl using STDIN

[theSeeker03]

Is there a way to pass a variable from Perl script to a Java program, so that Java reads it using STDIN?

I can do it as command line argument, but I'd like to know how to do it through STDIN.

 

[toolkit]

If you're using UNIX, you can try something like:

test.pl | xargs java Test

This will place stdout from the test.pl script onto the end of the java Test line. A more concrete example:

test.pl:
#!/usr/bin/perl -w
printf "1 2 3 4 5 6\n";
printf "a b c d e f\n";

Test.java:
public class Test {
    public static void main(String[] args) {
        for(int i = 0; i < args.length; i++) {
            System.out.println("args["+i+"] = "+args[i]);
        }
    }
}

Running this will produce:

$ test.pl  | xargs java Test
args[0] = 1
args[1] = 2
args[2] = 3
args[3] = 4
args[4] = 5
args[5] = 6
args[6] = a
args[7] = b
args[8] = c
args[9] = d
args[10] = e
args[11] = f

Do a man xargs for more information. Cheers, Neil

 

[toolkit]

Ug. Sorry, overcomplicated. If you want Java to read in STDIN, try something like:

import java.io.*;
public class Test {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String line = null;
        while ((line = br.readLine()) != null) {
            System.out.println("read line: "+line);
        }
    }
}

And then pipe from perl directly to Java using:

test.pl | java Test

Cheers, Neil

 

[theSeeker03]

Thanks for the information. More precisely, I am trying to obtain the STDIN to a Perl Script, then from the Perl script, make a system call to execute a java componenet, passing along the stardard input as STDIN, not as a parameter.

#!/usr/bin/perl 
# stdin.pl
my $var = "";
while ()
{
	chomp $_;
	$_ =~ s/^ *//;
	$_ =~ s/ *$//;
	$var = $var . $_;
}

my $command = "java helloWorld";

$rval = system($command);

open (FILEHANDLE, ">/tmp/out.txt");
print FILEHANDLE "$var";
print FILEHANDLE "$rval";
close (FILEHANDLE);

This is what I have tried, how can I pass the contents of $var to the java class so that helloWorld can read the STDIN using System.in

 

[toolkit]

Aha. Now I see. Try this:

#!/usr/bin/perl -w
use IPC::Open2;
open2 (*README, *WRITEME, "java Test");
if (fork) {
    print "sending stdin to Java\n";
    while (<STDIN>) {
        print WRITEME $_;
    }
}
else {
    print "reading stdout from Java\n";
    while (<README>) {
        print "java returned: $_";
    }
}

Cheers, Neil