How to invoke a Linux shell command from Java

Question

I am trying to execute some Linux commands from Java using redirection (>&) and pipes (|). How can Java invoke csh or bash commands?

I tried to use this:

Process p = Runtime.getRuntime().exec("shell command"); 

But it's not compatible with redirections or pipes.

Answer 1

exec does not execute a command in your shell

try

Process p = Runtime.getRuntime().exec(new String[]{"csh","-c","cat /home/narek/pk.txt"}); 

instead.

EDIT:: I don't have csh on my system so I used bash instead. The following worked for me

Process p = Runtime.getRuntime().exec(new String[]{"bash","-c","ls /home/XXX"}); 

Answer 2

Use ProcessBuilder to separate commands and arguments instead of spaces. This should work regardless of shell used:

import java.io.BufferedReader; import java.io.File; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.List;  public class Test {      public static void main(final String[] args) throws IOException, InterruptedException {         //Build command          List<String> commands = new ArrayList<String>();         commands.add("/bin/cat");         //Add arguments         commands.add("/home/narek/pk.txt");         System.out.println(commands);          //Run macro on target         ProcessBuilder pb = new ProcessBuilder(commands);         pb.directory(new File("/home/narek"));         pb.redirectErrorStream(true);         Process process = pb.start();          //Read output         StringBuilder out = new StringBuilder();         BufferedReader br = new BufferedReader(new InputStreamReader(process.getInputStream()));         String line = null, previous = null;         while ((line = br.readLine()) != null)             if (!line.equals(previous)) {                 previous = line;                 out.append(line).append('\n');                 System.out.println(line);             }          //Check result         if (process.waitFor() == 0) {             System.out.println("Success!");             System.exit(0);         }          //Abnormal termination: Log command parameters and output and throw ExecutionException         System.err.println(commands);         System.err.println(out.toString());         System.exit(1);     } }