Executing custom Commands in Java

Question

With this, we can execute "build in" commands in java. However if we want to run some custom commands from this , Changing "pwd" to "device_id -l" doesn't work. "device_id -l" should list all the ids of attached devices of currently host. if "device_id -l" is executed in terminal itself. it works fine. There is not a question for the "build in" bash commands. Thank you.

    String cmd = "pwd";
    Runtime run = Runtime.getRuntime();
    Process pr = run.exec(cmd);      
    pr.waitFor();

    BufferedReader buf = new BufferedReader(new InputStreamReader(pr.getInputStream()));
    String line = "";
    while ((line=buf.readLine())!=null)      
        System.out.println(line);

We can excuate

Answer 1

You can try using ProcessBuilder .

// create process
ProcessBuilder pb = new ProcessBuilder("/bin/bash", "-c", "device_id", "-l");
// start process
Process p = pb.start();
// wait for process exit
p.waitFor();

// read process output
BufferedReader buf = new BufferedReader(newInputStreamReader(p.getInputStream()));
String line = "";
while ((line=buf.readLine())!=null)
    System.out.println(line);

Answer 2

You need to split your command+arguments to a String array. In your case, if you want to execute "device_id -l", split that into an array like this:

String[] cmd = new String[] {"/full/path/to/device_id", "-l"};
Process pr = Runtime.getRuntime().exec(cmd);

And, you might want to use ProcessBuilder .

String[] cmd = new String[] {"/full/path/to/device_id", "-l"};
ProcessBuilder pb = new ProcessBuilder(cmd);
Process pr = pb.start();

Finally, you'll have to take into account that Java does not look for executables in PATH (like command shell does), you'll have to provide full path to the executable/script that you want to execute (or it has to be in the working directory; you can set the working directory with ProcessBuilder.directory(File) ).

See also: Difference between ProcessBuilder and Runtime.exec()