See "react --help"
react.py /tmp -p '*.txt' 'echo $f'
This is a simple test. Execute the above command and create and modify directories and files in /tmp. For every file ending with .txt its full path is printed on the console every time this file is created or changed.
react.py ../ -p '*.hs' ./runTests
The main motivation of this tool was to be able to trigger the execution of a test suite each time a source file of the project is modified. This speeds up my vim-based software development a lot.
react.py /srv/www/team 'setfacl -m g:team:rwx $f'
A major disadvantage of default file ACLs is that it only reacts on newly created files. If you move a file into a directory with a default ACL entry, this file's ACL entries are not updated. In practice this means that sooner or later every default-ACL-based control management will break. With react you can circumvent this problem.