Java

SSH Exec (Execute Command Line)

Demonstrates running a single command on an SSH server with an exec request and retrieving its output. The example connects, authenticates, opens a session channel, sends the command, reads until the server closes the channel, and then checks the exit status.

Background: exec is the workhorse of SSH automation: it runs one command and the server closes the channel when the command exits, which is a definitive end-of-output signal. No PTY is involved, so the shell runs non-interactively — no prompt, no echoed input, no ANSI escape codes — giving clean, parseable output. Remember that an accepted exec request only means the request was accepted; the command's own success is reported through the channel exit status. Command syntax depends on the remote shell, which is the user's default shell on Linux/UNIX and usually CMD.EXE on Windows SSH servers.

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import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Ssh;

public class ChilkatExample {

    public static void main(String[] args) {
        // This example requires the Chilkat API to have been previously unlocked.
        // See Global Unlock Sample for sample code.

        // Demonstrates running a single command on an SSH server with an exec request and retrieving
        // its output.  An exec request runs one command and the server closes the channel when it
        // finishes -- no PTY and no shell prompt are involved, so the output is clean and parseable.

        Ssh ssh = new Ssh();

        // The hostname may be a hostname or an IP address.
        String hostname = "ssh.example.com";
        int port = 22;
        try {
            ssh.connect(hostname, port);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Normally you would not hard-code the password in source.  You should instead obtain it
        // from an interactive prompt, environment variable, or a secrets vault.
        String password = "mySshPassword";

        try {
            ssh.authenticatePw("mySshLogin", password);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Open a session channel.  Several session channels may be open at once on one connection.
        int channelNum = ssh.openSessionChannel();
        if (channelNum < 0) {
            System.out.println(ssh.getLastErrorText());
            return;
        }

        // The command syntax depends on the remote system's shell.  On Linux/UNIX it is typically the
        // user's default shell; on Windows SSH servers it is usually CMD.EXE.
        //   Linux/UNIX:  "ls -l /tmp"        or  "cd /etc; ls -la"
        //   Windows:     "dir"               or  "\"cd \\temp&&dir\""
        String cmdOutput;
        try {
            ssh.sendReqExec(channelNum, "ls -l /tmp");

            // IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
            // it, this call waits forever if the server never sends channel close.
            ssh.setReadTimeoutMs(15000);

            // Read the output until the server sends channel close, which happens when the command exits.
            ssh.channelReceiveToClose(channelNum);

            cmdOutput = ssh.getReceivedText(channelNum, "utf-8");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println(cmdOutput);

        // An accepted exec request does not mean the command succeeded.  Check the exit status.
        if (ssh.channelReceivedExitStatus(channelNum)) {
            System.out.println("Exit status: " + ssh.getChannelExitStatus(channelNum));
        }

        ssh.disconnect();
    }
}