FAM(File Alteration Monitor)

PHP: ファイル改変監視関数（FAM) - Manual
http://jp2.php.net/manual/ja/ref.fam.php

SGI - Developer Central Open Source | FAM
http://oss.sgi.com/projects/fam/

Solaris FAM packages
http://kepler.acns.bethel.edu/~bjn/fam/