B4X

Start a Remote Shell with QuickShell

Demonstrates the Chilkat Ssh.QuickShell method, which starts a remote shell using the simplified sequence OpenSessionChannel → SendReqPty → SendReqShell. It takes no arguments and returns the shell channel number, or -1 on failure. The default PTY size is 80 columns by 24 rows.

Background: Note that QuickShell does allocate a PTY, so unlike a bare SendReqShell the remote shell runs interactively: it prints a command prompt, echoes the commands you send, and runs interactive login scripts. That is convenient for terminal-style work but means the output contains prompts and echoed input that scripted parsing must tolerate. The method returns as soon as the shell request is accepted — it does not consume the initial login text or prompt, so read and discard that before relying on command output.

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B4X

Dim success As Boolean = False

'  Demonstrates the Ssh.QuickShell method, which starts a remote shell using the simplified
'  sequence OpenSessionChannel, SendReqPty, and SendReqShell.  It takes no arguments and returns
'  the shell channel number, or -1 on failure.  The default PTY size is 80 columns by 24 rows.

Dim ssh As ChilkatSsh
ssh.Initialize("ssh")

Dim sshPort As Int = 22
success = ssh.Connect("ssh.example.com", sshPort)
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


'  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.
Dim password As String = "mySshPassword"

success = ssh.AuthenticatePw("mySshLogin", password)
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


'  Start the shell.  Note that QuickShell allocates a PTY, so the remote shell runs
'  interactively: it prints a command prompt and echoes the commands that are sent to it.
Dim channelNum As Int = ssh.QuickShell
If channelNum < 0 Then
    Log(ssh.LastErrorText)
    Return
End If


'  QuickShell returns as soon as the shell request is accepted -- it does not wait for or
'  consume the initial login text or prompt.
success = ssh.ChannelSendString(channelNum, "uname -a; echo DONE_MARKER" & Chr(10), "utf-8")
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


'  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

Dim caseSensitive As Boolean = False
success = ssh.ChannelReceiveUntilMatch(channelNum, "DONE_MARKER", "utf-8", caseSensitive)
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


Dim output As String = ssh.GetReceivedText(channelNum, "utf-8")
If ssh.LastMethodSuccess = False Then
    Log(ssh.LastErrorText)
    Return
End If

Log(output)

ssh.Disconnect