How to automatically launch a shell script when content of a given directory is changed

Question

I'm developing a web project using some libraries that force me to launch a shell command to compile some files everytime i modify them.

This task is obviously tiresome and i'm looking to find some script to handle it (I'm on OSX).

Is there a way to automatically launch a shell script when content of a given directory (+subdirs) is changed?

This depends on your operating system. On Linux, use inotifywait (see e.g. http://superuser.com/questions/181517/how-to-execute-a-command-whenever-a-file-changes). — Gilles 'SO- stop being evil', Aug 30 '10 at 07:03

score 5 · Accepted Answer · edited Mar 20 '17 at 10:17

Mac OSX has two filesystem notification APIs: kqueue and FSEvents. I don't know about commands that give you access to them without programming. There is a python binding for FSEvents.

See also View Filesystem Access in Real Time on Mac OS X.

Given what you're trying to do, you might want to try a different approach: rather than trigger a recompile when the source files have been modified, trigger a recompile when the compiled files are requested (using make, so that nothing is actually recompiled if the source files haven't changed). This may be too costly if you have to do this for every request to a web site, though; benchmark to find out.

I used the python bindings for FSEvents and it worked (http://gist.github.com/558970), thanks! — systempuntoout, Aug 31 '10 at 12:55

score 1 · Answer 2 · edited Dec 15 '11 at 10:46

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The BSD command wait_on based on kqueie is available in MacPorts, it provides just what you need.

The wait_on command allows shell scripts to access the facilities provided by kqueue(3). This allows scripts to detect files being added to directories, data appended to files and many other things - all without polling.

In Linux I would use incron, INotify Cron.

edited Dec 15 '11 at 10:46

ramn

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answered Aug 30 '10 at 08:12

Janne Pikkarainen

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score 1 · Answer 3 · edited Feb 08 '23 at 00:05

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Guard - is a cross-platform robust tool for watching directories (not just files) and running commands whenever files are added, modified or deleted.

It handles a mass of issues related to watching files, both OSX-specific and general file/directory watching problems.

It's also simple to setup and get running, and it uses the Listen library for watching files.

edited Feb 08 '23 at 00:05

RayB

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answered Jul 04 '15 at 12:22

Cezary Baginski

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score 0 · Answer 4 · answered Feb 07 '23 at 21:58

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As of 2023, I'd recommend looking at fswatch or guard, which both work on many platforms.

answered Feb 07 '23 at 21:58

RayB

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score 0 · Answer 5 · answered Aug 30 '10 at 07:00

Not really, but you can get close. You can write a script that checks to see if the files in a directory have changed (probably by checking them against a file somewhere), and if so, build them.

Then, you can set cron to run this script every 10 minutes, so you know your stuff is no more than 10 minutes old.

How to automatically launch a shell script when content of a given directory is changed

5 Answers5