File alteration monitor

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In computing, the File Alteration Monitor, also known as FAM and sgi_fam, provides a subsystem developed by Silicon Graphics for Unix-like operating systems. The FAM subsystem allows applications to watch certain files and be notified when they were modified. This greatly aids the applications, because before FAM existed, such applications would have to read the disk repeatedly to detect any changes: this resulted in high disk and CPU usage.

For example, a file manager application can detect if some file has changed and can then update a displayed icon and/or filename.

The FAM system consists of two parts:

famd — the FAM Daemon, which provides notifications and listens for requests. Administrators can configure it by editing the file /etc/fam.conf
libfam — the interface to the client

Although FAM may seem unnecessary now that many newer kernels include built-in notification support (inotify in Linux, for example), using FAM provides two benefits:

Consistently using FAM enables applications to work on a greater variety of platforms, agnostic of the kernel
FAM is network aware, and if a monitor is started on an NFS share, it will attempt to contact a FAM server on the NFS server and have it monitor the file locally, which is more efficient