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I'm looking for a way to rerun a specific command as soon as any of the files in a subdirectory (perhaps minus selected excludes) changes.

Use case

I'm working on a project that is self-contained in a directory. This project can be compiled, say, using make. I want to use the idle time of my machine to repeatedly compile the project. One option is to call make once per second, e.g., using watch (1). However, if make fails, it will usually fail whenever it's executed again, thus wasting CPU processing power (and, more importantly, heating up my laptop computer).

Instead, there should be a process that watches all files and runs make (or whatever other tool) only after anything changes in the directory where the project lives.

Existing solutions

Others have asked: Can a bash script be hooked to a file? There's inotifywait (1), but it doesn't appear to have a nice interface for repeating a command. Also, there's entr (1) which looks like the way to go, but a closer inspection of the project's website reveals that

[i]t was determined early on that entr would not implement it's own file search syntax, relying on standard Unix tools instead.

I'm lazy. I don't want to write a loop for my repeated invocation of make. Is there a higher-level magic tool that allows me to write

magic make

with the effect that make is rerun everytime anything in the current directory changes?

NB: It would be ideal if this magic tool was aware of the inevitable race condition that ensues when using inotify: Changes that occur after issuing the call but before a watch is established. I'm not sure if entr can do this, it looks like this feature requires keeping track of some kind of snapshot of at least the timestamps of all affected files.

SHAMELESS SELF-PROMOTION: My own four-liner that (somewhat) accomplishes this is called rpt and is far from perfect, I'd like to know if I'm duplicating effort here.

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  • So I can uderstand you need to check file|directory changing and if so do some action(s). As for me it is usual task which can be provided via few tools, for example cron (to start check) + find (to modification check).
    – Costas
    Mar 7, 2015 at 17:09
  • @Costas: The action should start immediately after changing files (perhaps after some configurable small delay).
    – krlmlr
    Mar 7, 2015 at 17:28
  • 1
    OK, forget cron(which can start check every minute), use watch instead (to check every second).
    – Costas
    Mar 7, 2015 at 17:35
  • Additionally you can provide check by files hash-sum instead of modification time.
    – Costas
    Mar 7, 2015 at 17:38
  • @Costas: Added some detail about my use case to the question.
    – krlmlr
    Mar 7, 2015 at 17:45

1 Answer 1

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Perhaps ls <dir> | entr make <file> would work. Only inotifywait will pick up creation of files.

If you need to pass filenames use info in comments from this answer: https://unix.stackexchange.com/a/81704/346155

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