4.20.2.3. Parameters of the SSH requests

SSH requests can be controlled using the server_request and client_request hashes. These hashes are indexed by the channel type (e.g.: session). Some requests have additional parameters that are also listed. Some channels (e.g., the X11 channel) require two request messages to open, the first message requests the channel, while the second message actually opens the requested channel. The following requests are available from the client side. For examples on local and remote forwarding, see Section 4.20.2.4, Configuring local and remote forwarding.

window-change
When the window (terminal) size changes on the client side a message may be sent to inform the server of the new window dimensions. Parameters of the request:
width_colsWidth of the terminal window in characters.
height_rowsHeight of the terminal window in characters.
width_pxWidth of the terminal window in pixels.
height_pxHeight of the terminal window in pixels.
pty-req
Request a pseudo-terminal for the session. Parameters of the request:
termRequests a pseudo-terminal.
width_colsWidth of the terminal window in characters.
height_rowsHeight of the terminal window in characters.
width_pxWidth of the terminal window in pixels.
height_pxHeight of the terminal window in pixels.
x11-req
Request X11 forwarding for the session. Parameters of the request:
x11_auth_protoThe name of the X11 authentication method used, e.g., MIT-MAGIC-COOKIE-1.
x11_auth_cookie 
screen_number 
single_connectionIf set to TRUE, the server forwards only a single connection.
x11
Open an X11 channel. Parameters of the request:
originator_hostIP address of the host.
originator_portPort number of the host.
auth-agent-req
Request the forwarding of the authentication requests. This request has no additional parameters.
auth-agent-req@openssh.com
Request the forwarding of the authentication requests, as implemented in OpenSSH. This request has no additional parameters.
env
Pass an environment variable and its value in the message. Parameters of the request:
nameThe name of environment variable.
valueThe value of environment variable.
shell
Request a shell be started on the server side. This request has no additional parameters.
exec
Request the server to start the execution of the command sent in the message. Parameters of the request:
commandThe command to be executed. The command may include a path.
subsystem
Request the server to execute a predefined subsystem. (Subsystems usually include a general file transfer mechanism, and possibly other features as well.) Parameters of the request:
subsystemName of the subsystem to be executed.
signal
A signal delivered to the remote process or service. Parameters of the request:
signalName of the signal to be sent.

The following requests are available from the server side. Some requests have additional parameters that are also listed.

exit-status
When the command running on the server terminates, an exit-status message can be sent to return the exit status of the command.
exit_status 
exit-signal
A message indicating that the remote command was terminated violently due to a signal. A zero usually means that the command terminated successfully.
signal_nameName of the signal. One of: ABRT, ALRM, FPE, HUP, ILL, INT, KILL, PIPE, QUIT, SEGV, TERM, USR1, USR2, or a custom signal consisting of two strings and the @ character (e.g., signal@ example).
core_dumped 
errorThe text of the error message. The message may consist of multiple lines separated by CRLF (Carriage Return - Line Feed) pairs.
langLanguage tag confirming to RFC3066.
xon-xoff
A message informing the client when it can or cannot perform flow control.
client_can_doTRUE if the client can perform flow control.
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