Top (Unix)

In most Unix-like operating systems, the top command produces a frequently-updated list of processes. The processes are ordered by amount CPU usage, with only the "top" CPU consumers shown. The top command 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.

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

For a non-realtime list of processes, see ps.

History

The top command was inspired by the monitor process/topcpu command found in the VMS operating system. William LeFebvre wrote the first implementation of top in April of 1984 for BSD 4.1 while a graduate student at Rice University. It was released as an Open Source project under the BSD license, which allowed it to be included in numerous proprietary BSD and UNIX operating systems.

The top command has been reimplemented several times for different operating systems and under different licenses.

The first top for Linux was written by Roger Binns; the most recent and common Linux version is a full-color windowed implementation by James C. Warner that ships with the procps package.

See also

External links

Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification.
..... Click the link for more information.
central processing unit (CPU), or sometimes simply processor, is the component in a digital computer capable of executing a program.(Knott 1974) It interprets computer program instructions and processes data.
..... Click the link for more information.
A system administrator, systems administrator, or sysadmin, is a person employed to maintain, and operate a computer system or network. System administrators may be members of an information technology department.
..... Click the link for more information.
In most Unix-like operating systems, ps is a program that displays the currently running processes.

ps has many options. On operating systems that support the UNIX and POSIX standards, ps is commonly run with the options -ef, where "-e" selects e
..... Click the link for more information.
An operating system (OS) is the software that manages the sharing of the resources of a computer. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the
..... Click the link for more information.
William Marsh Rice University (commonly called Rice University and opened in 1912 as The William Marsh Rice Institute for the Advancement of Letters, Science and Art
..... Click the link for more information.
Open source is a set of principles and practices that promote access to the design and production of goods and knowledge. The term is most commonly applied to the source code of software that is available to the general public with relaxed or non-existent intellectual property
..... Click the link for more information.
"New" BSD License
Author: Regents of the University of California
Version: N/A
Copyright on the license: Public Domain
Publication date: ?
OSI approved: Yes
Debian approved: Yes
Free Software: Yes

..... Click the link for more information.
In most Unix-like operating systems, ps is a program that displays the currently running processes.

ps has many options. On operating systems that support the UNIX and POSIX standards, ps is commonly run with the options -ef, where "-e" selects e
..... Click the link for more information.
vmstat (virtual memory statistics) is a computer operating system monitoring tool that collects and displays summary information about memory, processes, interrupts, paging and block I/O information.
..... Click the link for more information.
Printing: lp Communications: inetd netstat ping rlogin nc traceroute Searching: find grep strings Miscellaneous: banner bc cal dd man size yes
..... Click the link for more information.
In UNIX computing, the system load is a measure of the amount of work that a computer system is doing. The load average is the average system load over a period of time.
..... Click the link for more information.
Unix (officially trademarked as UNIX®) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy.
..... Click the link for more information.
command line interface or CLI is a method of interacting with an operating system or software using a command line interpreter. This command line interpreter may be a text terminal, terminal emulator, or remote shell client such as PuTTY.
..... Click the link for more information.
Printing: lp Communications: inetd netstat ping rlogin nc traceroute Searching: find grep strings Miscellaneous: banner bc cal dd man size yes
..... Click the link for more information.
The cat command is a standard Unix program used to concatenate and display files. The name is from , a synonym of concatenate.

Specification

The Single Unix Specification specifies the behavior that each of the files given in sequence as arguments will write their
..... Click the link for more information.
chattr is a UNIX program that allows a user to set certain attributes to a file. Mostly chattr is used to make files immutable so that password files and certain system files cannot be erased during software upgrades.
..... Click the link for more information.
cd, sometimes also available as chdir (change directory), is a command line command to change the current working directory in operating systems such as Unix, Windows and DOS.
..... Click the link for more information.
The chmod command (abbreviated from change mode) is a shell command in Unix and Unix-like environments.

When executed, the command can change file system modes of files and directories. The modes include permissions and special modes.
..... Click the link for more information.
The chown command is used on Unix-like systems to change the owner of a file. In most implementations, it can only be executed by the Superuser. Unprivileged (regular) users who wish to change the group of a file that they own may use chgrp.
..... Click the link for more information.
The chgrp command is used by unprivileged users on Unix-like systems to change the group associated with a file. Unlike the chown command, chgrp allows regular users to change groups, but only to one of which they are a member.
..... Click the link for more information.
cksum is a POSIX command that reads the files specified by the File parameter and calculates a checksum, cyclic redundancy check (CRC) and the byte count for a file or files. If no files are specified, the cksum command reads standard input.
..... Click the link for more information.
cmp is a command line utility for computer systems that use a Unix operating system. It compares two files of any type and writes the results to the standard output. By default, cmp is silent if the files are the same; if they differ, the byte and line number at which the first
..... Click the link for more information.

..... Click the link for more information.
du (abbreviated from disk usage) is a standard Unix program used to estimate the file space usage; space used under a particular directory or files on a file system.

History

The du utility first appeared in version 1 of AT&T UNIX.
..... Click the link for more information.
df (abbreviated from disk free) is a standard Unix computer program used to display the amount of available disk space for filesystems on which the invoking user has appropriate read access, df
..... Click the link for more information.
file is a standard Unix program for determining the type of data contained in a file.

History

The original version of file originated in Unix Research Version 4 in 1973.
..... Click the link for more information.
fuser is a UNIX command showing which processes are using a specified file.


..... Click the link for more information.
ln is a standard Unix program used to create links (link) to files.

Link files

Links allow more than one file to refer to the same file, elsewhere.
..... Click the link for more information.
LS may refer to:
  • Lightspeed Media Corporation, a collection of nude teen websites
  • .ls, the Internet top-level domain for Lesotho
  • ls is a command specified by POSIX and the Single UNIX Specification. It lists files.
  • Jet2.

..... Click the link for more information.


This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.