tshsh

tshsh (Terminal, SHell, SHell) lets you switch between several interactive shells while working in a single terminal.

It is a combination of:

• a simple terminal multiplexer that lets you switch between multiple shells without clearing terminal;
• a shell automation tool that can execute commands in interactive shells and separates command output from shell's prompt.

Status

tshsh is not ready for public release; refer to alpha1 section of roadmap to see what is missing.

Problem statement

High-level languages

• are great for scripting and interactive programming using a repl;
• aren't great as a replacement for an interactive shell such as bash, zsh, fish etc.

tshsh helps the user:

• to simultaneously work with two interactive shells (and get the best of the two worlds);
• automates synchronizing (copy-pasting) values from one shell to the other:
  • it synchronizes the current working directory;
  • it adds keyboard shortcuts to copy and paste the output of a previously executed command;
  • when it starts a new shell it takes the environment from a current shell.

An example. I like Haskell, and I often use it for small automation tasks. However, a Haskell interactive repl ghci lacks many features which my zsh setup has. So each time I am hacking on Haskell code, I keep two terminals, one for ghci and the other for zsh. Then I manually copy-paste values from one terminal to the other one. Instead of keeping two terminals, I might press Ctrl+z to suspend ghci and then resume it by using % but I still need to copy-paste between two shells ¯\_(ツ)_/¯.

Features

Here is a demo to demonstrate:

• switching between python and sh by pressing Ctrl-z;
• automatic synchronization of a working directory
• copying of a previous command output to clipboard;

First, we switch between python and sh by pressing Ctrl-z. Then we change directory and discover that after switching tshsh evaluates cd command to synchronize the current working directory. Then we evaluate "1+2" in python, switch to sh and discover that the clipboard contains the result of the last expression evaluated in python:

For more details see Features and Roadmap.

How does it work

.-----------.
| sh-4.4$ _ | <--- tshsh ---> sh
|           |                 python
'-----------'

^Z

.-----------.
| Type "help| <--- tshsh      sh
| >>>       |           \---> python
'-----------'

Under the hood, tshsh spawns shell processes and attaches them to virtual tty devices. Then it marshals input/output, signals back and forth and synchronizes tty state, terminal state(not implemented), and optionally chosen shells state (pwd, environment variables(not implemented), etc).

For more details see Design.

Goals

• non-intrusiveness: no source code or config modifications of puppet shells
• responsiveness (one can safely drop the program into ~/.bashrc without worrying about shell initialization time, responsiveness, and memory consumption).