Run cmd-line program with user input from Java

Question

public class Controller {

public String printResults(Process process) throws IOException {
    BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
    String line = "";
    String container = "";
    while ((line = reader.readLine()) != null) {
        container = container + line + "\n";
        System.out.println(line);
    }
    return container;
}

public String executeCmd(String firstname,  String lastname) throws IOException {
    
    String command = "./myprogram -n " + firstname + " -s " + lastname;
    Process p = Runtime.getRuntime().exec(command, null, new File("/home/user/myprogram/build/"));
    return "Hi, \n" + printResults(p);
}
}

This allowes me to run a single command with attributes from a specific directory and get back result.

However, I have a larger program, which asks user for inputs from terminal.

user@debian:~/program/build/$./program
...
Enter Value: 5
...
Enter Name: Hanz
...
Enter State: GE

Output..

How can I run that program and enter user input from Java?

Building a command as a string -- in any programming language -- is a fast route to serious security problems. The underlying OS interface on UNIX -- execve -- uses an array of strings; your code should do the same. Otherwise, you need to worry about whether you have, say, a firstname of $(rm -rf ~) — Charles Duffy
– Charles Duffy, Commented Nov 9, 2020 at 23:15

rzwitserloot · Accepted Answer · 2020-11-08 21:56:18Z

1

First, rewrite your code to use ProcessBuilder; it's pretty much just replacing exec with new ProcessBuilder.

That's because PB gives you some flexibility that may well come up. For example, you can redirect inputs and outputs to files, for example.

Then, run start() on the builder and this gets you a Process object. You can use this to get the OutputStream, and then you can write your string to that: p.getOutputStream().write("5\nHanz\GE".getBytes());

There are a couple of different ways to do the job; Have a look at the APIs of Process and ProcessBuilder, there's lots of interesting stuff in there :)

answered Nov 8, 2020 at 21:56

rzwitserloot

107k6 gold badges74 silver badges104 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Run cmd-line program with user input from Java

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related