Executing a shell scripts that takes an input during execution with Java

Question

I am trying to execute shell script in Java. I was able to achieve this in the following manner.

        ProcessBuilder pb = new ProcessBuilder("/path_to/my_script.sh");
        pb.redirectOutput(new File("/new_path/out.txt"));
        Process p = pb.start();
        try {
            p.waitFor();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

How would I give user input if the shell requires user input? How to implement this?

example: my_script.sh

#!/bin/bash
read -p "Enter your name : " name
echo "Hi, $name. Let us be friends!"

I need to give input of name through Java.

Do you need to provide user input only when the script is launched in order to pass arguments to your script or while it is running ? — Aserre
– Aserre, Commented Mar 5, 2018 at 10:58

Nahuel Fouilleul · Accepted Answer · 2018-03-06 16:14:19Z

1

EDIT following comments

    // writing to file
    String input = "Bob";
    try ( PrintWriter out = new PrintWriter( filename ) ) {
        out.print( input );
    }

    // redirecting input from file
    pb.redirectInput( new File( filename ) );
    pb.redirectOutput( Redirect.INHERIT );

Initial answer;

Depending on how it is launch, following may be sufficient

pb.redirectInput( Redirect.INHERIT );

However to see message, output should also be redirected to std out

pb.redirectOutput( Redirect.INHERIT );

and tee output maybe done from shell

exec 6>&1 1> >(tee /new_path/out.txt)  # start tee output to out.txt (save current output to file descriptor 6 for example)
...
exec >&6      # end to restore standard output and terminate tee process

Note about InterruptedException, it should not be catched and continue the program, but propagated until point where task is really finished.

edited Mar 6, 2018 at 16:14

answered Mar 5, 2018 at 11:45

Nahuel Fouilleul

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10 Comments

Abhishek Gangadhar Over a year ago

Could you please elaborate.. I didn't quite understand.

Nahuel Fouilleul Over a year ago

what did not you understand ? And how do you launch java program ?

Abhishek Gangadhar Over a year ago

I am running this on a java server, with javaEE

Nahuel Fouilleul Over a year ago

if you need to pass input while it's running you can't use System.in, how will you give input from client to server?

Abhishek Gangadhar Over a year ago

I can't change the script. I can take the input from the client side through request ajax call.

|

Abhijit Pritam Dutta · Accepted Answer · 2018-03-05 15:14:50Z

0

Hi You can do it like below:-

 String inputName = "blabla";
 String command = "/path_to/my_script.sh  " + inputName;
 Process p;
 try {
        p = Runtime.getRuntime().exec(command);
        p.waitFor();
    } catch (Exception ex) {
        ex.printStackTrace();
    }

Now you have to modify your shell script like below:-

#!/bin/bash
#read -p "Enter your name : " name
name = $1
echo "Hi, $name. Let us be friends!"

edited Mar 5, 2018 at 15:14

answered Mar 5, 2018 at 15:09

Abhijit Pritam Dutta

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2 Comments

Abhishek Gangadhar Over a year ago

@Abhijith Pritam I want it to take input where in I can't modify the shell script. Can you suggest any ways of doing that?

Abhijit Pritam Dutta Over a year ago

No idea. Try with below answer.

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