World Library  
Flag as Inappropriate
Email this Article

Dnotify

Article Id: WHEBN0002594691
Reproduction Date:

Title: Dnotify  
Author: World Heritage Encyclopedia
Language: English
Subject: Inotify, Linux kernel, Gamin, Kernel same-page merging, Evdev
Collection: Linux Kernel Features
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Dnotify

dnotify is a file system event monitor for the Linux kernel, one of the subfeatures of the fcntl call. It was introduced in the 2.4 kernel series.[1] It has been obsoleted by inotify, but will be retained for compatibility reasons.

Its function is essentially an extension to filesystems to notice changes to the filesystem, and report those changes to applications. Instead of application checking for changes to filesystem, application can register to be notified by kernel when changes to filesystem occur. Application can select directories to monitor and types of changes to be notified for.

One major use is in desktop search utilities like Beagle, where its functionality permits reindexing of changed files without scanning the filesystem for changes every few minutes, which would be very inefficient. By being told that a file has changed directly by the kernel, rather than actively looking, Beagle and such utilities can achieve change-to-reindexing times of only about a second, with very small performance hits (dnotify therefore enables the use of such programs in a sensible manner; daemons are generally not accepted by distributors if they drain system performance noticeably to provide userland functionality).

Limitations

  • dnotify can only watch directories.
  • dnotify requires maintaining an open file descriptor to the directory that the user wants to watch. First, the directory is open, hence disallowing the device on which it resides from being unmounted. Second, watchlist is limited by open file limit of the process.[2]

Footnotes

  1. ^ Namely, in 2.4.0-test9.
  2. ^ "Kernel Korner - Intro to inotify". Linux Journal. Retrieved 25 April 2012. 

See also

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.