SSH Exec (Execute Command Line)

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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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bool success = false;

//  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.

Chilkat.Ssh ssh = new Chilkat.Ssh();

//  The hostname may be a hostname or an IP address.
string hostname = "ssh.example.com";
int port = 22;
success = ssh.Connect(hostname,port);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    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";

success = ssh.AuthenticatePw("mySshLogin",password);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

//  Open a session channel.  Several session channels may be open at once on one connection.
int channelNum = ssh.OpenSessionChannel();
if (channelNum < 0) {
    Debug.WriteLine(ssh.LastErrorText);
    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\""
success = ssh.SendReqExec(channelNum,"ls -l /tmp");
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

//  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.ReadTimeoutMs = 15000;

//  Read the output until the server sends channel close, which happens when the command exits.
success = ssh.ChannelReceiveToClose(channelNum);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

string cmdOutput = ssh.GetReceivedText(channelNum,"utf-8");
if (ssh.LastMethodSuccess == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

Debug.WriteLine(cmdOutput);

//  An accepted exec request does not mean the command succeeded.  Check the exit status.
if (ssh.ChannelReceivedExitStatus(channelNum)) {
    Debug.WriteLine("Exit status: " + Convert.ToString(ssh.GetChannelExitStatus(channelNum)));
}

ssh.Disconnect();