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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    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.

    ssh := chilkat.NewSsh()

    sshPort := 22
    success = ssh.Connect("ssh.example.com",sshPort)
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        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.
    password := "mySshPassword"

    success = ssh.AuthenticatePw("mySshLogin",password)
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

    //  Open a session channel.  A negative return value indicates failure.
    channelNum := ssh.OpenSessionChannel()
    if channelNum < 0 {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

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

    success = ssh.SendReqSetEnv(channelNum,"MY_APP_MODE","production")
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

    //  Now run the command, which sees the requested environment.
    success = ssh.SendReqExec(channelNum,"echo $MY_APP_MODE")
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        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.SetReadTimeoutMs(15000)

    success = ssh.ChannelReceiveToClose(channelNum)
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

    output := ssh.GetReceivedText(channelNum,"utf-8")
    if ssh.LastMethodSuccess() == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

    fmt.Println(*output)

    ssh.Disconnect()

    ssh.DisposeSsh()