how to run a command at terminal from java program?

Question

I need to run a command at terminal in Fedora 16 from a JAVA program. I tried using

Runtime.getRuntime().exec("xterm"); 

but this just opens the terminal, i am unable to execute any command.

I also tried this:

OutputStream out = null;
Process proc = new ProcessBuilder("xterm").start();
out = proc.getOutputStream();  
out.write("any command".getBytes());  
out.flush(); 

but still i can only open the terminal, but can't run the command. Any ideas as to how to do it?

Answer 1

You need to run it using bash executable like this:

Runtime.getRuntime().exec("/bin/bash -c your_command");

Update: As suggested by xav, it is advisable to use ProcessBuilder instead:

String[] args = new String[] {"/bin/bash", "-c", "your_command", "with", "args"};
Process proc = new ProcessBuilder(args).start();

Answer 2

I vote for Karthik T's answer. you don't need to open a terminal to run commands.

For example,

// file: RunShellCommandFromJava.java
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class RunShellCommandFromJava {

    public static void main(String[] args) {

        String command = "ping -c 3 www.google.com";

        Process proc = Runtime.getRuntime().exec(command);

        // Read the output

        BufferedReader reader =  
              new BufferedReader(new InputStreamReader(proc.getInputStream()));

        String line = "";
        while((line = reader.readLine()) != null) {
            System.out.print(line + "\n");
        }

        proc.waitFor();   

    }
} 

The output:

$ javac RunShellCommandFromJava.java
$ java RunShellCommandFromJava
PING http://google.com (123.125.81.12): 56 data bytes
64 bytes from 123.125.81.12: icmp_seq=0 ttl=59 time=108.771 ms
64 bytes from 123.125.81.12: icmp_seq=1 ttl=59 time=119.601 ms
64 bytes from 123.125.81.12: icmp_seq=2 ttl=59 time=11.004 ms

--- http://google.com ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 11.004/79.792/119.601/48.841 ms

Answer 3

You don't actually need to run a command from an xterm session, you can run it directly:

String[] arguments = new String[] {"/path/to/executable", "arg0", "arg1", "etc"};
Process proc = new ProcessBuilder(arguments).start();

If the process responds interactively to the input stream, and you want to inject values, then do what you did before:

OutputStream out = proc.getOutputStream();  
out.write("command\n");  
out.flush();

Don't forget the '\n' at the end though as most apps will use it to identify the end of a single command's input.

Answer 4

As others said, you may run your external program without xterm. However, if you want to run it in a terminal window, e.g. to let the user interact with it, xterm allows you to specify the program to run as parameter.

xterm -e any command

In Java code this becomes:

String[] command = { "xterm", "-e", "my", "command", "with", "parameters" };
Runtime.getRuntime().exec(command);

Or, using ProcessBuilder:

String[] command = { "xterm", "-e", "my", "command", "with", "parameters" };
Process proc = new ProcessBuilder(command).start();

Answer 5

I don't know why, but for some reason, the "/bin/bash" version didn't work for me. Instead, the simpler version worked, following the example given here at Oracle Docs.

String[] args = new String[] {"ping", "www.google.com"};
Process proc = new ProcessBuilder(args).start();