Write an executable .sh file with Java for OSX

Question

So I am trying to write an .sh file that will be executable, this is how I'm currently writing it:

Writer output = null;

try {
  output = new BufferedWriter(new FileWriter(file2));
  output.write(shellScriptContent);
  output.close();
} catch (IOException ex) {
  Logger.getLogger(PunchGUI.class.getName()).log(Level.SEVERE, null, ex);
}

So that writes the file just fine, but it is not executable. Is there a way to change the executable status when I write it?

Edit: To further clarify, I am trying to make it execute by default, so that for instance, if you double clicked the generated file, it would automatically execute.

Answer 1

You'd need to chmod it, and you can probably do it by exec'ing a system command like such:

Really all you'd need is to fire off something like this:

Runtime.getRuntime().exec("chmod u+x "+FILENAME);

But if you want to keep track of it more explicitly can capture stdin / stderr then something more like:

Process p = Runtime.getRuntime().exec("chmod u+x "+FILENAME);
BufferedReader stdInput = new BufferedReader(new InputStreamReader(p.getInputStream()));    
BufferedReader stdError = new BufferedReader(new InputStreamReader(p.getErrorStream()));

Which I got from here: http://www.devdaily.com/java/edu/pj/pj010016/pj010016.shtml

Update:

Test program:

package junk;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;

public class Main{
  private String scriptContent = '#!/bin/bash \n echo "yeah toast!" > /tmp/toast.txt';
  public void doIt(){
    try{
      Writer output = new BufferedWriter(new FileWriter("/tmp/toast.sh"));
      output.write(scriptContent);
      output.close();
      Runtime.getRuntime().exec("chmod u+x /tmp/toast.sh");
    }catch (IOException ex){}
  }

  public static void main(String[] args){
    Main m = new Main();
    m.doIt();
  }

}

On linux if you open up a file browser and double click on /tmp/toast.sh and choose to run it, it should generate a text file /tmp/toast.txt with the words 'yeah toast'. I assume Mac would do the same since it's BSD under the hood.

Answer 2

You can call File.setExecutable() to set the owner's executable bit for the file, which might be sufficient for your case. Or you can just chmod it yourself with a system call with Process.

Alas, full-powered programmatic alteration of file permissions isn't available until Java 7. It'll be part of the New IO feature set, which you can read more about here.

Answer 3

On Mac OS X, besides chmod +x, you have to give a .command extension to your shell script if you want to launch it with a double-click.

Answer 4

This answer I wrote for the question how do I programmatically change file permissions shows a chmod example via a native call using jna, which should work on Mac OS X.