JSCH execute and print command output sequentially

Question

Jsch in shell mode i want to execute commands sequentially. I tried using the below code. Problem with the code is code waits on readLine(). Can anybody suggest a solution. If you can please fix the below code

Note: i want to execute the commands in shell mode only

public class SSHClient1 {

    private  Session session;
    private  ChannelShell channel;
    private  String username = "";
    private  String password = "";
    private  String hostname = "";

    public SSHClient1(String username, String password, String hostname) throws Exception {
        super();
        this.username = username;
        this.password = password;
        this.hostname = hostname;
        startSession();
        intializeChannel();
    }

    private void startSession() throws Exception{
        if(session == null || !session.isConnected()){
            session = connect(hostname,username,password);
        }
    }

    private void intializeChannel() throws Exception{
        if(channel == null || !channel.isConnected()){
            try{
                channel = (ChannelShell)session.openChannel("shell");
                channel.setPty(false);
                channel.connect();
            }catch(Exception e){
            }
        }
    }

    private Session connect(String hostname, String username, String password) throws Exception{
        JSch jSch = new JSch();
        try {
            session = jSch.getSession(username, hostname, 22);
            Properties config = new Properties(); 
            config.put("StrictHostKeyChecking", "no");
            session.setConfig(config);
            session.setPassword(password);
            session.connect();
            System.out.println("Connected successfully to host "+ hostname);
        }catch(Exception e){
        }
        return session;
    }

    public void executeCommands(List<String> commands) throws Exception{
        PrintStream out = null;
        try{
            out = new PrintStream(channel.getOutputStream());
            for(String command : commands){
                out.println(command);
                out.flush();
                printResult();
            }

        }catch(Exception e){
        } finally{
            if(out != null)
                out.close();

        }
    }

    private void printResult() throws IOException{
        try{
            InputStream in = channel.getInputStream();
            String line = "";
            BufferedReader br =new  BufferedReader(new InputStreamReader(in));
            while((line = br.readLine()) != null){
                System.out.println(line);
            }
        }catch(Exception e){
        }

    }


    public void close(){ 
        if(channel != null)
            channel.disconnect();
        if(session != null)
            session.disconnect();
    }


    public static void main(String[] args) throws Exception{

        SSHClient1 ssh = new SSHClient1("admin", "password", "192.168.2.9");
        List<String> commands = new ArrayList<String>();
        commands.add("enable");
        commands.add("configure terminal");
        commands.add("show running-config");
        ssh.executeCommands(commands);
        ssh.close();

    }
}

if i change two methods of the above code i was able to achieve what i want, the problem with the approach is i need to put a Thread.sleep after creating the buffer other wise it will not print any thing.

public void executeCommands(List<String> commands) throws Exception{
        PrintStream out = null;
        try{
            out = new PrintStream(channel.getOutputStream(),true);
            for(String command : commands){
                out.println(command);
                out.flush();
                printResult();
            }
        }catch(Exception e){
        } finally{
            if(out != null)
                out.close();

        }
    }

    private void printResult() throws IOException{
        try{
            InputStream in = channel.getInputStream();
            BufferedReader br =new  BufferedReader(new InputStreamReader(in));
            Thread.sleep(10000);
            boolean ready = false;
            int c = 0;
            StringBuilder line = new StringBuilder();
            while((ready = br.ready()) == true){
                ready = br.ready();
                c = br.read();
                System.out.print(String.valueOf((char)c));
            }
        }catch(Exception e){
        }
    }

Yair Harel · Accepted Answer · 2016-02-21 15:25:54Z

1

if wrapping the commands is an option, you can do :

# cat /usr/bin/your-enable
#!/bin/bash
enable
echo "#END#"

change main (example):

 commands.add("/usr/bin/your-enable");

change printResult :

while((line = br.readLine()) != null){

    if (line.equals("#END#")) {
       break;
    } else {
       System.out.println(line);
    }
}

Hope it helps.

answered Feb 21, 2016 at 15:25

Yair Harel

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3 Comments

Phoebe Buffay Over a year ago

Yair in my case that is not possible.

Yair Harel Over a year ago

so you can add new command which will separate your commands : "echo "#END#"" and use the same code in the printResult. you will have to send 2 command each time before going to read.

Phoebe Buffay Over a year ago

i am not working on a linux machine. its a ssh enabled router which has only few commands. Secondly in my case br.readLine itself pauses

Phoebe Buffay · Accepted Answer · 2016-02-21 19:03:06Z

0

Was able to find a solution. Has put a busy spin until br.ready() is true. We need to put a Thread.sleep also before putting a busy loop

answered Feb 21, 2016 at 19:03

Phoebe Buffay

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