World Library  
Flag as Inappropriate
Email this Article

Top (software)

Article Id: WHEBN0000686137
Reproduction Date:

Title: Top (software)  
Author: World Heritage Encyclopedia
Language: English
Subject: Pkill, Top (disambiguation), Sysctl, NetBSD, Whereis
Collection: System Administration, Unix Process and Task Management-Related Software
Publisher: World Heritage Encyclopedia

Top (software)

Stable release 3.2.8
Written in C
Operating system Unix-like
Type Process Viewer / System monitor
License BSD Licenses#3-clause (Unix version), GNU General Public License (Linux version)



top (table of processes) is a task manager program found in many Unix-like operating systems. It produces an ordered list of running processes selected by user-specified criteria, and updates it periodically. Default ordering is by CPU usage, and only the top CPU consumers are shown. top shows how much processing power and memory are being used, as well as other information about the running processes. Some versions of top allow extensive customization of the display, such as choice of columns or sorting method.

There are several different versions of top. The traditional Unix version was written by William LeFebvre and originally copyrighted in 1984.[1] It is hosted on sourceforge,[2] and release 3.7 was announced in 2008.[3]

The Linux top version is part of the procps-ng group of tools. It was originally written by Roger Binn in 1991[4] but shortly thereafter it was taken over by others.[5]

top is useful for system administrators, as it shows which users and processes are consuming the most system resources at any given time.

On Solaris, the roughly equivalent program is prstat. MS-DOS has tasklist and graphical Microsoft operating systems have the Windows Task Manager. IBM AIX has an updating running processes list as part of the topas and topas_nmon commands.

The load average numbers in Linux refers to the sum of the number of processes waiting in the run-queue plus the number currently executing. The number is absolute, not relative. And thus it can be unbounded; unlike utilization. The instant variations of the number of processes are damped with a exponential decay formula which is calculated using fixed point math.[6]

The ps program is similar to top, but instead produces a snapshot of processes taken at the time of invocation.

See also

  • Htop — interactive system-monitor process-viewer written for Linux
  • nmon — a system monitor tool for the AIX and Linux operating systems.

External links

  • FreeBSD top(1)
  • BSD top home page and man page
  • Linux top home page (procps-ng) and man page
  • Alternate top programs for Linux include atop (uses process accounting) and Htop


  1. ^ Unixtop license.
  2. ^ Unixtop FAQ.
  3. ^ SourceForge Unixtop News.
  4. ^ Linux top man page
  5. ^ Linux Top Origins.
  6. ^ "UNIX Load Average Part 2: Not Your Average Average" (PDF). 2010. Retrieved 2013-06-10. 
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, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for 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.