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Joe Dog Software

Proudly serving the Internets since 1999

Fido Home


Fido is a multi-threaded file watch utility. It can monitor files for changes in content or modification times. If it notices a change, it will kick off a user-defined script.

Content changes can be recognized with regular expression pattern matches. For example, you can monitor a jboss or tomcat log file for out of memory errors with this pattern: .*OutOfMemory.* Here’s an example which demonstrates how to use Fido to kick off jobs on a pattern match.

Along with content changes, Fido can monitor a file or directory to see if its modification time changed. It’s smart enough to recognize a change even if the daemon was down at the time of the change. This example shows how to use fido to kick off jobs after an FTP upload.


Fido was written for RedHat Enterprise Linux but it should run in all Linux flavors. The source bundle contains RedHat init.d scripts for your convenience. This software was not tested on other platforms but it was coded to POSIX 1003.1 standards.

FIDO-1.1.2 19 Aug 2014 9:27 – This release fixes a bug introduced in the previous version. Under certain conditions fido would miss age tests and fail to fire an alert. All fido users should update to this version.
FIDO-1.1.0 17 Oct 2013 23:21 — This release adds several new features. It can now test to see whether a file or the contents of a directory are older than a particular date. It can throttle its alerts so you don’t flood an inbox or a network node manager. It also contains several minor bugfixes
FIDO-1.0.8 04 Mar 2013 23:57 –This release features a functional change. Fido will no longer exit if a configured file doesn’t exist. It will happily cycle and start to monitor the file once it appears. This release also features several significant bugfixes. All users should upgrade to 1.0.8
FIDO-1.0.7 May 22 14:08:33 EDT 2012 — This release adds the ability to watch a file or directory by its modification date. If the file changes, fido launches a script.

FIDO-1.0.6 Feb 15 21:54:20 EST 2012 — This release adds new command line options for more flexibility.

FIDO-1.0.5 Jan 25 18:06:08 EST 2012 — This is the first public release.