Set an Environment Variable on an SSH Channel

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Demonstrates the Chilkat Ssh.SendReqSetEnv method, which asks the server to set an environment variable for a session channel. The arguments are the channel number, the variable name, and its value. Send these requests before the exec, shell, or subsystem request.

Background: This is the clean way to pass configuration to a remote command without embedding it in the command line. Be aware that many SSH servers restrict which variables clients may set (OpenSSH's AcceptEnv), so a request can be silently ignored or rejected — do not rely on it without verifying the server's policy.

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bool success = false;

//  Demonstrates the Ssh.SendReqSetEnv method, which asks the server to set an environment
//  variable for a session channel.  The 1st argument is the channel number, the 2nd is the
//  variable name, and the 3rd is its value.  Send it before the exec, shell, or subsystem
//  request.

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

int sshPort = 22;
success = ssh.Connect("ssh.example.com",sshPort);
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.  A negative return value indicates failure.
int channelNum = ssh.OpenSessionChannel();
if (channelNum < 0) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

//  Set environment variables for the channel.  Multiple variables may be requested.
success = ssh.SendReqSetEnv(channelNum,"LANG","en_US.UTF-8");
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

success = ssh.SendReqSetEnv(channelNum,"MY_APP_MODE","production");
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

//  Now run the command, which sees the requested environment.
success = ssh.SendReqExec(channelNum,"echo $MY_APP_MODE");
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;

success = ssh.ChannelReceiveToClose(channelNum);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

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

Debug.WriteLine(output);

ssh.Disconnect();