Java program to execute shell scripts on remote server

If you want to execute shell scripts on remote server and get output with the help of your java program then you are at right place. In this tutorial we will be using Java secure channel ( Jsch ) to log on to remote server, execute the shell script and capture the output. JSch is a pure Java implementation of SSH2. ( download jSch ).

We will be using this library for our program. Download the jar and add to your build path. Once you have added it to your build path you will be able to make secure connections to server. It requires java version 1.4 or greater. I would highly recommend to go through the requirements for this library on their official website ( http://www.jcraft.com/jsch/ ).

Program :

package service;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import com.jcraft.jsch.ChannelExec;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;

/**
 * This class executes the shell script on the remote server
 * Requires the jSch java library
 * @author Saket kumar
 *
 */

public class ShellExecuter{
 
 private static String USERNAME ="root"; // username for remote host
 private static String PASSWORD ="password"; // password of the remote host
 private static String host = "113.33.111.111"; // remote host address
 private static int port=22;
    
 /**
  * This method will execute the script file on the server.
  * This takes file name to be executed as an argument
  * The result will be returned in the form of the list
  * @param scriptFileName
  * @return
  */
 public List<string> executeFile(String scriptFileName)
 {
     List<string> result = new ArrayList<string>();
     try
     {

         /**
         * Create a new Jsch object
         * This object will execute shell commands or scripts on server
         */
         JSch jsch = new JSch();

         /*
         * Open a new session, with your username, host and port
         * Set the password and call connect.
         * session.connect() opens a new connection to remote SSH server.
         * Once the connection is established, you can initiate a new channel.
         * this channel is needed to connect to remotely execution program
         */
         Session session = jsch.getSession(USERNAME, host, port);
         session.setConfig("StrictHostKeyChecking", "no");
         session.setPassword(PASSWORD);
         session.connect();

         //create the excution channel over the session
         ChannelExec channelExec = (ChannelExec)session.openChannel("exec");

         // Gets an InputStream for this channel. All data arriving in as messages from the remote side can be read from this stream.
         InputStream in = channelExec.getInputStream();

         // Set the command that you want to execute
         // In our case its the remote shell script
         channelExec.setCommand("sh "+scriptFileName);

         // Execute the command
         channelExec.connect();

         // Read the output from the input stream we set above
         BufferedReader reader = new BufferedReader(new InputStreamReader(in));
         String line;
         
         //Read each line from the buffered reader and add it to result list
         // You can also simple print the result here 
         while ((line = reader.readLine()) != null)
         {
             result.add(line);
         }

         //retrieve the exit status of the remote command corresponding to this channel
         int exitStatus = channelExec.getExitStatus();

         //Safely disconnect channel and disconnect session. If not done then it may cause resource leak
         channelExec.disconnect();
         session.disconnect();

         if(exitStatus < 0){
            // System.out.println("Done, but exit status not set!");
         }
         else if(exitStatus > 0){
            // System.out.println("Done, but with error!");
         }
         else{
            // System.out.println("Done!");
         }

     }
     catch(Exception e)
     {
         System.err.println("Error: " + e);
     }
     return result;
 }
 
}