B4X

Run a Command on an SSH Session Channel

Demonstrates the Chilkat Ssh.SendReqExec method, which requests execution of a command on a session channel. The first argument is the channel number and the second is the command line. This example runs a command, reads the output until the channel closes, and prints it.

Background: exec is the workhorse for automation: run one command, collect its output, and finish — no interactive shell needed. Note carefully that a true return means the request was accepted, not that the command succeeded. To learn the command's outcome, read its output and check the channel exit status.

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Dim success As Boolean = False

'  Demonstrates the Ssh.SendReqExec method, which requests execution of a command on a session
'  channel.  The 1st argument is the channel number and the 2nd is the command line.

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


'  Open a session channel.  A negative return value indicates failure.
Dim channelNum As Int = ssh.OpenSessionChannel
If channelNum < 0 Then
    Log(ssh.LastErrorText)
    Return
End If


'  Request execution of a command.  A True return means the server accepted the request; it
'  does not mean the command itself succeeded.
success = ssh.SendReqExec(channelNum, "ls -l /tmp")
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


'  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 command output until the server closes the channel.
success = ssh.ChannelReceiveToClose(channelNum)
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