Do something when a file is changed

Question

When I write a LaTeX document, I find myself to press F6 in my editor to compile often. Or when I use SASS, I often type make to convert my .scss into .css.

Now I would like to let the machine do the dirty work and run make or something else every time a given file change.

So far I kept a terminal window open and pressed arrow-up and return. Or I used watch make, but that seems like an odd solution.

Is there a nice way on Linux to do something when a given file changes?

Answer 1

You're looking for inotifywait, part of inotify-tools. There are some examples of how to use it on the project's site but a simple approach is,

while true; do inotifywait code.cpp -e modify; make; done

the key part of which is,

inotifywait code.cpp -e modify

That command will wait until code.cpp is modified then exit. Put in the infinite loop and followed with make causes it to constantly rebuild after every modification.

Besides waiting on modify, you can wait on creation, deletion, access, opening, closing, and more. I highly recommend looking at the project examples and inotifywait man page for some other ideas on how it can be used.

Answer 2

Have a look at incron, a cron-like package that responds to filesystem events, instead of time events. The package consists of a daemon (incrond) and a table manipulator (incrontab), analogous to the well-known crond/crontab pair of cron.

With incron, you could easily arrange to run make whenever particular files and/or directories are modified.

Answer 3

Rather than watch make, how about watch ls? Then just make when the timestamp changes.