top (table of processes) is a

task manager In operating systems, a task manager is a system monitor program used to provide information about the processes and applications running on a computer, as well as the general status of the computer. Some implementations can also be used to ...

program, found in many

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

operating systems, that displays information about CPU and memory utilization.

Overview

The program produces an ordered list of running processes selected by user-specified criteria, and updates it periodically. Default ordering is by

CPU A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, and ...

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. top is useful for

system administrator A system administrator, or sysadmin, or admin is a person who is responsible for the upkeep, configuration, and reliable operation of computer systems, especially multi-user computers, such as servers. The system administrator seeks to en ...

s, as it shows which users and processes are consuming the most system resources at any given time. Top-with-altered-settings

Implementations

There are several different versions of top. The traditional Unix version was written by William LeFebvre and originally copyrighted in 1984. It is hosted on

SourceForge SourceForge is a web service that offers software consumers a centralized online location to control and manage open-source software projects and research business software. It provides source code repository hosting, bug tracking, mirrori ...

, and release 3.7 was announced in 2008. The Linux version of top is part of the procps-ng group of tools. It was originally written by Roger Binns but shortly thereafter taken over by others. On Solaris, the roughly equivalent program is prstat. Microsoft Windows has the tasklist command and the graphical

Task Manager In operating systems, a task manager is a system monitor program used to provide information about the processes and applications running on a computer, as well as the general status of the computer. Some implementations can also be used to ...

utility.

IBM AIX AIX (Advanced Interactive eXecutive, pronounced , "ay-eye-ex") is a series of proprietary Unix operating systems developed and sold by IBM for several of its computer platforms. Background Originally released for the IBM RT PC RISC w ...

has an updating running processes list as part of the topas and

topas_nmon nmon (''Nigel's Monitor'') is a computer performance system monitor tool for the AIX and Linux operating systems. The nmon tool has two modes a) displays the performance stats on-screen in a condensed format or b) the same stats are saved to a c ...

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 an

exponential decay A quantity is subject to exponential decay if it decreases at a rate proportional to its current value. Symbolically, this process can be expressed by the following differential equation, where is the quantity and (lambda) is a positive rate ...

formula which is calculated using fixed point math. The ps program is similar to top, but instead produces a snapshot of processes taken at the time of invocation. top's (number of iterations) option can product a similar result, causing the program to run the specified number of iterations, then exit after printing its output.

References

External links

* * *
Unix Top

Customizing top
{{Unix commands Console applications Unix process- and task-management-related software System administration System monitors Task managers

Overview

Implementations

See also

References

External links