pty

pty

I wrote this mainly for personal use for working on linux machines from my macOS desktop. Github is a convenient way to import it on my corporate appliance. As this is a personal project it has some areas that might be a little messy and is very short on godoc comments. pty is only supported on Linux as it utilizes /proc.

Typical invocation: ssh -t remotehost path-to-pty

pty is a screen like program for managing sessions on a remote machine. It uses <ctrl-p> as the escape character. <ctrl-p>. is used to disconnect. Use <ctrl-p>: to execute a pty command. The commands are:

  dump   - dump stack
  env    - display environment variables
  excl   - detach all other clients
  list   - list all clients
  ps     - display processes on this pty
  save   - save buffer to FILE
  setenv - forward environment variables
  ssh    - forward SSH_AUTH_SOCK
  tee    - tee all future output to FILE (- to close)
  title  - display/set session title

pty is both a client and server. The first time pty is called (or anytime when there are no sessions) it will ask for a session:

Name of session to create (or shell): 

Specifying shell just execs your login shell (you should have just used ssh without pty). The session name must not contain slashes. Once a session name is chosen, pty will fork and fork again itself as a pty server. The server spawns an interactive shell. The original pty (the client) then connects to the server forwards standard in/out/error between the login shell and the client. The connection is over TCP on the loopback interface (127.0.0.1). The address of the server is written to $HOME/.pty/session-SESSION-NAME. If there are sessions existing, pty asks you to select a session:

Current sessions:
   -1) Spawn /usr/bin/ksh
    0) Create a new session
    1) debugging (1 Client)
         pty 368978 (~)
          ⬑ [-ksh] (~)
            ⬑ vi [interesting.go] (~)
Please select a session: 

This shows there is only one pty session available and it is editing the file interesting.go. It is possible for multiple clients to be attached to a single pty session, though visual editing can become interesting.

When connecting to an existing session the SSH_AUTH_SOCK environment variable will be incorrect. Using <ctrl-p>:ssh at a shell prompt will send SSH_AUTH_SOCK=... as if you had typed it. You can use the general setenv command to send other environment variables.

pty keeps its log files in $HOME/.pty/log.