Fly through your shell history. Great Scott!
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McFly - fly through your shell history


McFly replaces your default ctrl-r Bash history search with an intelligent search engine that takes into account your working directory and the context of recently executed commands. McFly's suggestions are prioritized in real time with a small neural network.

TL;DR: an upgraded ctrl-r for Bash whose history results make sense for what you're working on right now.


  • Rebinds ctrl-r to bring up a full-screen reverse history search prioritized with a small neural network.
  • Augments your shell history to track command exit status, timestamp, and execution directory in a SQLite database.
  • Maintains your normal Bash history file as well so that you can stop using McFly whenever you want.
  • Unicode support throughout.
  • Includes a simple action to scrub any history item from the McFly database and your shell history files.
  • Designed to be extensible for other shells in the future.
  • Written in Rust, so it's fast and safe.


The key feature of McFly is smart command prioritization powered by a small neural network that runs in real time. The goal is for the command you want to run to always be one of the top suggestions.

When suggesting a command, McFly takes into consideration:

  • The directory where you ran the command. You're likely to run that command in the same directory in the future.
  • What commands you typed before the command (e.g., the command's execution context).
  • How often you run the command.
  • When you last ran the command.
  • If you've selected the command in McFly before.
  • The command's historical exit status. You probably don't want to run old failed commands.


Install with Homebrew (on OS X or Linux)

  1. Install the tap:
    brew tap cantino/mcfly
  2. Install mcfly:
    brew install mcfly
  3. Add the following to your ~/.bashrc file:
    if [[ -f "$(brew --prefix)/opt/mcfly/mcfly.bash" ]]; then
      source "$(brew --prefix)/opt/mcfly/mcfly.bash"
  4. Run . ~/.bashrc or restart your terminal emulator.

Uninstalling with Homebrew

  1. Remove mcfly:
    brew uninstall mcfly
  2. Remove the tap:
    brew untap cantino/mcfly
  3. Remove the lines you added to ~/.bashrc.

Installing manually from GitHub

  1. Download the latest release from GitHub.
  2. Install to a location in your $PATH. (For example, you could create a directory at ~/bin, copy mcfly to this location, and add export PATH="$PATH:$HOME/bin" to your .bashrc.)
  3. Copy mcfly.bash to a known location.
  4. Add the following to your ~/.bashrc file:
    if [[ -f /path/to/mcfly.bash ]]; then
      source /path/to/mcfly.bash
  5. Run . ~/.bashrc or restart your terminal emulator.

Install manually from source

  1. Install Rust 1.29 or later
  2. Run git clone and cd mcfly
  3. Run cargo install --path .
  4. Ensure ~/.cargo/bin is in your $PATH.
  5. Add the following to your ~/.bashrc file:
    if [[ -f /path/to/mcfly.bash ]]; then
      source /path/to/mcfly.bash
  6. Run . ~/.bashrc or restart your terminal emulator.


To avoid McFly's UI messing up your scrollback history in iTerm2, make sure this option is unchecked:

iterm2 UI instructions

Light Mode

To swap the color scheme for use in a light terminal, set the environment variable MCFLY_LIGHT.

For example, add the following to your ~/.bash_profile:


Possible Future Features

  • Add a screencast to README.
  • Learn common command options and autocomplete them in the suggestion UI?
  • Sort command line args when coming up with the template matching string.
  • Possible prioritization improvements:
    • Cross validation & explicit training set selection.
    • Learn command embeddings


Running tests

cargo test


  1. Edit Cargo.toml and bump the version.
  2. git tag vx.x.x
  3. git ci -m 'Bumping to vx.x.x'
  4. git push origin head --tags
  5. Let the build finish.
  6. Edit the new Release on Github.
  7. Edit pkg/brew/mcfly.rb and update the version and SHAs. (shasum -a 256 ...)