I built a file watcher in Rust that's faster than watchexec (and way faster than nodemon)

Hey r/rust! 👋

I've been working on a file watcher called Flash and wanted to share it with the community. I know there are already great tools like watchexec out there, but I had some specific needs that led me to build this.

What it does

Think nodemon but more general purpose and written in Rust. It watches files and runs commands when they change - pretty standard stuff.

Why I built it

I was frustrated with slow startup times when using file watchers in my development workflow. Even a few extra milliseconds add up when you're restarting processes hundreds of times a day. I also wanted something with better glob pattern support and YAML config files.

The numbers (please don't roast me if I messed up the benchmarks 😅)

Startup: ~2.1ms (vs 3.6ms for watchexec, ~35ms for nodemon)
Binary size: 1.9MB (vs 6.7MB for watchexec)
Memory: Pretty low footprint

I used hyperfine for timing and tried to be fair with the comparisons, but I'm sure there are edge cases I missed.

What makes it different

Fast mode: --fast flag skips unnecessary output for maximum speed
Flexible patterns: Good glob support with include/exclude patterns
Config files: YAML configs for complex setups
Process management: Can restart long-running processes or spawn new ones
Built-in stats: Performance monitoring if you're into that

Example usage

# Basic usage
flash -w "src/**/*.rs" -c "cargo test"

# Web dev with restart
flash -w "src/**" -e "js,jsx,ts" -r -c "npm start"

# With config file
flash -f flash.yaml

The honest truth

It's not revolutionary - file watchers are a solved problem
Probably has bugs I haven't found yet
The "blazingly fast" claim might be a bit much, but hey, it's Rust 🦀
I'm sure there are better ways to do some things

What I'd love feedback on

Performance: Did I benchmark this fairly? Any obvious optimizations I missed?
API design: Does the CLI feel intuitive?
Use cases: What features would actually be useful vs just bloat?
Code quality: Always looking to improve my Rust

I built a file watcher in Rust that's faster than watchexec (and way faster than nodemon) - would love feedback