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Auto-rerun With entr

Feed entr a file list and it reruns your command on every change.

macOSwatchautomationcliLow risk
Run ls *.py | entr -c python3 app.py to restart the app when a Python file changes.

01Command

Command
$ ls *.py | entr -c python3 app.py

02What it does

entr is a tiny Unix utility that waits for file changes on standard input and runs the given command. The -c flag clears the screen between runs, -d exits when a new file is added, and -r restarts a long-running process.

03Risk

RiskLow risk
CompatibilitymacOS with Homebrew installed
!Warning: It only watches files you list, so new files are not picked up unless you use a shell glob that is re-evaluated or -d.

04Undo

✓No undo needed — this command does not change persistent state.

05Sources

  • Homebrew formula: entr
    Homebrew · vendor-doc · 2026-09-20
    Evidence: Packages entr, which runs a command when the piped files change.

Last verified: 2026-09-22 · Category: Developer