Java

Get the Exit Status of a Remote SSH Command

Demonstrates the Chilkat Ssh.GetChannelExitStatus method, which returns the remote process exit status for a channel. The only argument is the channel number. Call it only after ChannelReceivedExitStatus returns true.

Background: The exit status is how you learn whether a remote command actually succeeded — recall that a successful exec request only means the request was accepted. By Unix convention 0 means success and any nonzero value indicates a failure. Retrieve it promptly after the receive operation and before calling unrelated SSH methods or releasing the channel, since the completed channel record can be discarded.

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

public class ChilkatExample {

    public static void main(String[] args) {
        // Demonstrates the Ssh.GetChannelExitStatus method, which returns the remote process exit
        // status for a channel.  The only argument is the channel number.  Call it only after
        // ChannelReceivedExitStatus returns true.

        Ssh ssh = new Ssh();

        int sshPort = 22;
        try {
            ssh.connect("ssh.example.com", sshPort);
        } 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;
        }

        int channelNum = ssh.openSessionChannel();
        if (channelNum < 0) {
            System.out.println(ssh.getLastErrorText());
            return;
        }

        try {
            ssh.sendReqExec(channelNum, "grep -q root /etc/passwd");

            // 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);

            ssh.channelReceiveToClose(channelNum);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Retrieve the exit status immediately, before calling unrelated SSH methods or releasing the
        // channel, because the completed channel record can be discarded.
        if (ssh.channelReceivedExitStatus(channelNum)) {
            int exitStatus = ssh.getChannelExitStatus(channelNum);
            System.out.println("Exit status: " + exitStatus);

            // By convention, 0 means the remote command succeeded.
            if (exitStatus == 0) {
                System.out.println("The remote command succeeded.");
            } else {
                System.out.println("The remote command reported a failure.");
            }
        }

        ssh.disconnect();
    }
}