Running a bash shell script in java

Question

I want to run a shell script from my program below but it doesn't seem to do anything. I've run the same command directly in the linux terminal and it works fine so I'm guessing it's my java code. As you can see, I was first writing the command to the shell script using a PrintWriter but I expect that this would not effect the running of the shell script itself. Any help would be appreciated!

    public static void main(String[] args) {
    // TODO Auto-generated method stub

    String nfdump = "nfdump -o csv -r /home/shane/Documents/nfdump/nfcapd.201211211526>blank.txt";

    try {
        FileWriter fw = new FileWriter("/home/shane/Documents/script.sh");

        PrintWriter pw = new PrintWriter(fw);

        pw.println("#!/bin/bash");
        pw.println(nfdump);

        pw.close();
    } catch (IOException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

    Process proc = null;

    try {
        proc = Runtime.getRuntime().exec("sh /home/shane/Documents/script.sh");
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

Have a look at ProcessBuilder instead of Runtime.getRuntime()... When I use this I seem to have fewer problems and things appear a bit more undestandable — RNJ, Dec 04 '12 at 16:36
I want to be able to use nfdump from my GUI, it's part of the software I'm building — Shane, Dec 04 '12 at 16:43

score 30 · Accepted Answer · edited May 23 '17 at 11:54

You should use the returned Process to get the result.

Runtime#exec executes the command as a separate process and returns an object of type Process. You should call Process#waitFor so that your program waits until the new process finishes. Then, you can invoke Process.html#getOutputStream() on the returned Process object to inspect the output of the executed command.

An alternative way of creating a process is to use ProcessBuilder.

Process p = new ProcessBuilder("myCommand", "myArg").start();

With a ProcessBuilder, you list the arguments of the command as separate arguments.

See Difference between ProcessBuilder and Runtime.exec() and ProcessBuilder vs Runtime.exec() to learn more about the differences between Runtime#exec and ProcessBuilder#start.

Actually, if you're looking to retrieve the output of a subprocess then you'd need to call [`Process#getInputStream()`](http://docs.oracle.com/javase/7/docs/api/java/lang/Process.html#getInputStream%28%29), which pipes to the process' output stream. — Geoffrey Tucker, May 29 '15 at 08:16

score 9 · Answer 2 · answered Feb 18 '13 at 09:15

When you execute a script from Java it spawns a new shell where the PATH environment variable is not set.

Setting the PATH env variable using the below code should run your script.

String[] env = {"PATH=/bin:/usr/bin/"};
String cmd = "you complete shell command";  //e.g test.sh -dparam1 -oout.txt
Process process = Runtime.getRuntime().exec(cmd, env);

score 8 · Answer 3 · answered Feb 08 '13 at 05:08

8

Try this, it will work.

String[] cmd = new String[]{"/bin/sh", "path/to/script.sh"};
Process pr = Runtime.getRuntime().exec(cmd);

answered Feb 08 '13 at 05:08

Suniel

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Running a bash shell script in java

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