How to pipe input from a Java program to another using Bourne Shell

Question

I have two simple Java programs and I want to pipe the result of the "Test" to the "Test2".

public class Test{
    public static void main(String args[]){
        System.out.println("Hello from Test");
    }
}

and

public class Test2{
    public static void main(String args[]){
        System.out.printf("Program Test piped me \"%s\"",args[0]);
    }
}

After I compiled both of .java files I tried to run the pipe command from terminal

java Test | java Test2, but I get an ArrayIndexOutOfBoundsException which means that the args array is not initialized?

How can the Test2 application take the outputstream value that Test.main() produced through piping?

Using > perhaps?

FDavidov
– FDavidov

2016-11-03 14:41:56 +00:00
Commented Nov 3, 2016 at 14:41 — FDavidov
– FDavidov, Commented Nov 3, 2016 at 14:41

VGR · Accepted Answer · 2016-11-03 14:54:47Z

4

Pipes connect one program’s standard output to another program’s standard input, not to the other program’s command-line arguments.

The second class will not get the piped output as arguments to its main method; it will get the piped output as its standard input. So you want to read the information from System.in:

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;

public class Test2 {
    public static void main(String args[])
    throws IOException {
        BufferedReader stdin =
            new BufferedReader(new InputStreamReader(System.in));
        stdin.lines().forEachOrdered(
            line -> String.format("Program Test piped me \"%s\"", line));
    }
}

answered Nov 3, 2016 at 14:54

VGR

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Comments

toootooo · Accepted Answer · 2016-11-03 14:47:32Z

3

One way is to use xargs:

java Test| xargs -I ARGS java Test2 ARGS

answered Nov 3, 2016 at 14:47

toootooo

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