kqwait

Waits for write/rename events on files or directories and returns.

Supports waiting on multiple files and one directory (i'm on it). When waiting on a directory adding a file, or deleting a file will trigger a return. Everything else (like touching or writing) wil not trigger a return.

This tool is inspired by inotifywait 1 and the original kqueue paper 2 and the lack of anything similar (to the best of my knowledge) on Mac OS X.

Requirements

Mac OS X

• Xcode

Linux

• http://mark.heily.com/libkqueue/

Waiting on directories does not work on Linux at the moment.

Build

To build this just type

make kqwait

Usage

Call it like this

kqwait <file>[ <file>]+

or this

kqwait <dir>[ <dir>]+

Prints the file or directory that caused the tool to wake up and returns 0 if the expected event occured, 1 otherwise.

When waiting on a dir a + character is prepended if a file was added, a - if a file was deleted.

Use it in a shell script like this:

while ./kqwait text.txt; do
   # do some stuff on write
done

Or watch directories like this:

$ while ./kqwait somedir someother; do true; done
+ somedir/a_file_was_added.txt
- someotherdir/a_file_was_deleted.txt

Note

There is (at least) one race condition in this code, when waiting for changes on directories. If several events happen on a directory in quick succession, this tool might catch an intermediate snapshot of that chain of events.

Author

Sven Schober sven.schober@uni-ulm.de