Tcl

Open an SSH Session Channel

Demonstrates the Chilkat Ssh.OpenSessionChannel method, which opens a new SSH session channel. It takes no arguments and returns the channel number, or -1 on failure. The transport must already be connected and authenticated.

Background: SSH multiplexes independent channels over one authenticated connection, and a session channel is the one used to run a command, start a shell, or invoke a subsystem. Opening the channel is only the container — nothing runs until you follow it with an exec, shell, or subsystem request. Always test for a negative return rather than assuming success.

Chilkat Tcl Downloads

Download Chilkat for Tcl

Tcl


load ./chilkat.dll

set success 0

#  Demonstrates the Ssh.OpenSessionChannel method, which opens a new SSH session channel.  It
#  takes no arguments and returns the channel number, or -1 on failure.  The transport must
#  already be connected and authenticated.

set ssh [new_CkSsh]

set sshPort 22
set success [CkSsh_Connect $ssh "ssh.example.com" $sshPort]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  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.
set password "mySshPassword"

set success [CkSsh_AuthenticatePw $ssh "mySshLogin" $password]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  Open a session channel.  A negative return value indicates failure.
set channelNum [CkSsh_OpenSessionChannel $ssh]
if {$channelNum < 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

puts "Opened session channel: $channelNum"

#  Opening the channel does not start a shell or command -- send an exec, shell, or subsystem
#  request next.

CkSsh_Disconnect $ssh

delete_CkSsh $ssh