Swift

SSH Remote Shell with Multiple Commands

Demonstrates running several commands one after another in a single remote shell session, retrieving each command's output separately. No PTY is requested, so each command is followed by an echoed marker that signals where its output ends.

Background: Interleaving commands and reads in one shell requires a way to know where each command's output stops. An interactive session would use the shell prompt, but without a PTY the shell is non-interactive and never prints one — so the dependable technique is to append echo SOME_MARKER to each command and read up to that marker. Retrieving the text also clears the receive buffer, which matters here: if a marker were left buffered, the next receive would match it immediately and return the wrong output.

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Swift


func chilkatTest() {
    var success: Bool = false

    //  This example requires the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    //  Demonstrates running several commands one after another in a single remote shell session,
    //  retrieving each command's output separately.
    //  
    //  No PTY is requested, so the shell runs non-interactively and never prints a command prompt.
    //  Because there is no prompt to synchronize on, each command is followed by an "echo" of a
    //  unique marker, and the output is read up to that marker.

    let ssh = CkoSsh()!

    var hostname: String? = "ssh.example.com"
    var port: Int = 22
    success = ssh.connect(hostname: hostname, port: port)
    if success == false {
        print("\(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.
    var password: String? = "mySshPassword"

    success = ssh.authenticatePw(login: "mySshLogin", password: password)
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    var channelNum: Int = ssh.openSessionChannel().intValue
    if channelNum < 0 {
        print("\(ssh.lastErrorText!)")
        return
    }

    //  Start a shell WITHOUT requesting a PTY.  Without a PTY the shell sees it is connected to a
    //  raw data pipe and enters non-interactive mode: it suppresses the command prompt, does not
    //  echo typed commands back, and skips interactive login scripts.  The output is therefore
    //  clean and easily parseable -- but because no prompt is ever sent, code must not wait for
    //  one.  Instead, have each command print a predictable marker, or wait for EOF / channel close.
    success = ssh.sendReqShell(channelNum: channelNum)
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    //  IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
    //  which means no limit -- without it, this call waits forever if the received data never
    //  contains a match.
    ssh.readTimeoutMs = 15000

    var caseSensitive: Bool = true

    //  ---- 1st command: change directory ----
    success = ssh.channelSendString(channelNum: channelNum, strData: "cd /tmp; echo END_OF_CMD_1\n", charset: "utf-8")
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    success = ssh.channelReceive(untilMatch: channelNum, matchPattern: "END_OF_CMD_1", charset: "utf-8", caseSensitive: caseSensitive)
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    //  Retrieving the text also clears the receive buffer, which matters: if the next marker were
    //  left in the buffer, the following receive would match immediately.
    var cmdOutput: String? = ssh.getReceivedText(channelNum: channelNum, charset: "utf-8")
    if ssh.lastMethodSuccess == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    print("\(cmdOutput!)")

    //  ---- 2nd command: directory listing ----
    success = ssh.channelSendString(channelNum: channelNum, strData: "ls; echo END_OF_CMD_2\n", charset: "utf-8")
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    success = ssh.channelReceive(untilMatch: channelNum, matchPattern: "END_OF_CMD_2", charset: "utf-8", caseSensitive: caseSensitive)
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    cmdOutput = ssh.getReceivedText(channelNum: channelNum, charset: "utf-8")
    if ssh.lastMethodSuccess == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    print("\(cmdOutput!)")

    //  ---- 3rd command: long listing, then finish the session ----
    success = ssh.channelSendString(channelNum: channelNum, strData: "ls -l\n", charset: "utf-8")
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    //  No more input will be sent.
    success = ssh.channelSendEof(channelNum: channelNum)
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    success = ssh.channelReceive(toClose: channelNum)
    if success == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    cmdOutput = ssh.getReceivedText(channelNum: channelNum, charset: "utf-8")
    if ssh.lastMethodSuccess == false {
        print("\(ssh.lastErrorText!)")
        return
    }

    print("\(cmdOutput!)")

    ssh.disconnect()

}