entr

entr [options] command [args...]

entr runs commands when files change. It watches files listed on stdin and executes the specified command whenever any change is detected.The tool is ideal for development workflows: rerunning tests, rebuilding projects, or restarting servers on source changes. The -r flag handles processes that need restart rather than re-execution.entr uses efficient kernel file notification mechanisms (kqueue, inotify) rather than polling.

COMMAND

Command to run when files change.

Clear the screen before running the command. Repeat as -cc to also clear the scrollback.

Reload a persistent child process, sending it SIGTERM before restarting it.

Postpone the first execution until a file actually changes.

Run the command through $SHELL and use its exit status.

Track directories: exit if a new file is added to a watched directory, so a wrapper loop can restart entr with the new file list.

Respond to all events instead of coalescing rapid changes into one.

Non-interactive: do not read from the terminal, so no space-to-rerun or q-to-quit.

One-shot mode: exit after the command completes.

Placeholder that expands to the file that changed.

The file list is read from stdin once at startup and never grows: -d makes entr exit when a new file appears in a watched directory, and the usual pattern is to wrap it in a shell loop such as `while sleep 0.1; do ls *.c | entr -d make; done`. Editors that save by writing a new file and renaming it over the old one replace the inode entr is watching, which is why -d or a rerun is often needed. The number of files is bounded by the system limit on open file descriptors.

entr was created by Eric Radman as a simple, Unix-philosophy tool for file watching. It focuses on doing one thing well: running commands when files change.

inotifywait(1), watchexec(1), fswatch(1)

Source code · Homepage