Hybrid of GNOME Do and Emacs ido mode for a standard VT100 terminal.

While working on my dissertation--which involved a lot of research-caliber rather than production-caliber C and C++--I went through an earnest phase of using vim rather than emacs with the goal of having fairly evaluated both. In the process, I began sorely missing Emacs's ido mode. At the same time, I was commonly working on Ubuntu systems where the GNOME Do application launcher was having a bit of a moment. This all led to my interest in creating a extensible, terminal-based ido-mode-like prompt.

term-do was largely duct-taped together as a means of procrastination in between doing other research tasks. I did, however, have a few things in mind while working on it:

1. Show completions as each character is typed in an ido-mode-style

2. Allow "rotating" through the completions with Ctrl+S and Ctrl+R.

3. Support completions from a variety of (pluggable) sources.

4. Fast startup time: Should be near-instantaneous to launch from a terminal; any delay would disincentivize use in favor of plain bash completion.

5. Portable with as few dependencies as possible.

These loose requirements spiraled into a series of elements that went into the (overengineered) design:

• Plugin system implemented as dynamic libraries, providing a mechanism to yield custom completions.

• Hand-rolled ternary search tree implementation for quickly identifying completions from a prefix.

• Bash history file parser for weighting commands such that common completions can be sorted in use-order.

• Optional client/server mode for even faster startup time on older hardware.

• A persistent mode where the process does not exit after the completed command is run, essentially functioning as a lightweight shell.

Because completions are implemented solely as plugins, the default plugins that are built and used are the launcher and dir plugins; other plugins are not included by default. The full list for reference:

• dir: Yields directory/file completions based on the current command.

• launcher: Reads the launcher configuration file which defines commands + possible completions. This configuration format became richer as time progressed to be a crude half-reimplementation of bash completion. Supports hardcoded completions as well as "parse the man page for flags" and "run command that generates completions" modes, including aliases with the _ prefix.

• rnd: adds random junk completions, for testing purposes.

• bash-comp: experimentation to shell out to bash and scrape it for bash completions directly; never worked quite as it needed to so I abandoned it for the launcher plugin instead.

Though I do not get as much use out of term-do these days, I've consistently packaged it for whatever OS I'm using so it's available. Notably, there is an AUR package and a NixOS derivation included in the pkgs folder of this repo. See this commit for an example of how to overlay the Nix derivation.

I found that having to type the term-do command to run it was cumbersome enough to discourage using the tool. So instead, I've mapped the command to the Emacs-esque M-x shortcut. This is done in bash using .inputrc with:

$if Bash
"\M-x": "term-do\C-M"
$endif

and for zsh using .zshrc with:

bindkey -s "^[x" 'term-do^M'

If you want term-do's cd functionality to bubble up to the current terminal, then you can wrap it in a shell function:

term-do() {command term-do "$*" && builtin cd $(cat ~/.term-do.d/pwd)}

The rest of the keyboard shortcuts are likely familiar to users of Emacs:

• C-s: rotate completions forward

• C-r: rotate completions backward

• tab: add current completion

• enter: run command
• C-f: remove current token and rebuild completions
• C-c, C-d, C-g: quit

There are better completion options these days, particularly in zsh, and term-do's code has bit-rotted significantly. But I still haven't found a terminal completion that matches ido-mode closely enough for my tastes. Hopefully one day I can resurrect term-do, possibly in the form of a zsh plugin or similar to fill this niche.