watchexec

Software development often involves running the same commands over and over. Boring!

watchexec is a simple, standalone tool that watches a path and runs a command whenever it detects modifications.

Example use cases:

• Automatically run unit tests
• Run linters/syntax checkers

Features

• Simple invocation and use
• Runs on OS X, Linux and Windows
• Monitors current directory and all subdirectories for changes
  • Uses most efficient event polling mechanism for your platform (except for BSD)
• Coalesces multiple filesystem events into one, for editors that use swap/backup files during saving
• By default, uses .gitignore to determine which files to ignore notifications for
• Support for watching files with a specific extension
• Support for filtering/ignoring events based on glob patterns
• Launches child processes in a new process group
• Sets the following environment variables in the child process:
  • If a single file changed (depending on the event type):
    • $WATCHEXEC_CREATED_PATH, the path of the file that was created
    • $WATCHEXEC_REMOVED_PATH, the path of the file that was removed
    • $WATCHEXEC_RENAMED_PATH, the path of the file that was renamed
    • $WATCHEXEC_WRITTEN_PATH, the path of the file that was modified
    • $WATCHEXEC_META_CHANGED_PATH, the path of the file whose metadata changed
  • If multiple files changed:
    • $WATCHEXEC_COMMON_PATH, the longest common path of all of the files that triggered a change
• Optionally clears screen between executions
• Optionally restarts the command with every modification (good for servers)
• Does not require a language runtime

Anti-Features

• Not tied to any particular language or ecosystem
• Does not require a cryptic command line involving xargs

Usage Examples

Watch all JavaScript, CSS and HTML files in the current directory and all subdirectories for changes, running make when a change is detected:

$ watchexec --exts js,css,html make

Call make test when any file changes in this directory/subdirectory, except for everything below target:

$ watchexec -i target make test

Call ls -la when any file changes in this directory/subdirectory:

$ watchexec -- ls -la

Call/restart python server.py when any Python file in the current directory (and all subdirectories) changes:

$ watchexec -e py -r python server.py

Call/restart my_server when any file in the current directory (and all subdirectories) changes, sending SIGKILL to stop the child process:

$ watchexec -r -s SIGKILL my_server

Send a SIGHUP to the child process upon changes (Note: with using -n | --no-shell here, we're executing my_server directly, instead of wrapping it in a shell:

$ watchexec -n -s SIGHUP my_server

Run make when any file changes, using the .gitignore file in the current directory to filter:

$ watchexec make

Run make when any file in lib or src changes:

$ watchexec -w lib -w src make

Installation

Cargo

watchexec requires Rust 1.38 or later. You can install it using cargo:

$ cargo install watchexec

OS X with Homebrew

$ brew install watchexec

Linux

For now, use the GitHub Releases tab to obtain the binary. PRs for packaging in unsupported distros are welcomed.

Debian

A deb package is available for amd64 architectures in the GitHub Releases.

Arch Linux

Available in the community repository:

$ pacman -S watchexec

Windows

Available using scoop:

#> scoop install watchexec

Or chocolatey:

#> choco install watchexec

Or just unzip the binary from the GitHub Releases.

Shell completions

Currently available shell completions:

• zsh: completions/zsh should be installed to /usr/share/zsh/site-functions/_watchexec

Building

Rust 1.38 or later is required.

Credits

• notify for doing most of the heavy-lifting
• globset for super-fast glob matching