Tcl

Request a Pseudo-Terminal (PTY) over SSH

Demonstrates the Chilkat Ssh.SendReqPty method, which requests a pseudo-terminal for a session channel. The arguments are the channel number, the terminal type, the character width and height, and the pixel width and height. It must be sent before the primary exec or shell request.

Background: A PTY makes the remote side behave as though a real terminal is attached, which matters for programs that draw screens, prompt for passwords, or colorize output — many refuse to run interactively without one. The terminal type (such as xterm) tells the remote program what escape sequences it may use. Pixel dimensions are commonly 0, meaning unspecified.

Chilkat Tcl Downloads

Download Chilkat for Tcl

Tcl


load ./chilkat.dll

set success 0

#  Demonstrates the Ssh.SendReqPty method, which requests a pseudo-terminal for a session
#  channel.  The 1st argument is the channel number, the 2nd is the terminal type, the 3rd and
#  4th are the character width and height, and the 5th and 6th are the pixel width and height.
#  It must be sent before the primary exec or shell request.

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
}

#  Request an 80x24 xterm.  Pixel dimensions of 0 mean unspecified.
set termType "xterm"
set widthInChars 80
set heightInChars 24
set widthInPixels 0
set heightInPixels 0
set success [CkSsh_SendReqPty $ssh $channelNum $termType $widthInChars $heightInChars $widthInPixels $heightInPixels]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  Start the shell now that the PTY is allocated.
set success [CkSsh_SendReqShell $ssh $channelNum]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

CkSsh_Disconnect $ssh

delete_CkSsh $ssh