NationMaster - Encyclopedia: AWK

AWK is a general purpose programming language that is designed for processing text-based data, either in files or data streams. The name AWK is derived from the family names of its authors — Alfred Aho, Peter Weinberger, and Brian Kernighan; however, it is not commonly pronounced as a string of separate letters but rather to sound the same as the name of the bird, auk (which acts as an emblem of the language such as on The AWK Programming Language book cover). awk, when written in all lowercase letters, refers to the Unix or Plan 9 program that runs other programs written in the AWK programming language. A programming paradigm is a paradigmatic style of programming (compare with a methodology, which is a paradigmatic style of doing software engineering). ... A scripting language, script language or extension language, is a programming language that controls software application. ... This article is about the computer programming paradigm. ... Event-driven programming is a computer programming paradigm. ... Dr. Alfred V. Aho is a computer scientist. ... Peter J. Weinberger is a computer scientist who worked at AT&T Bell Labs and contributed to the design of the pioneering AWK programming language (he is the W in AWK). ... Brian Wilson Kernighan (IPA pronunciation: , the g is silent), (born 1942 in Toronto, Ontario, Canada) is a computer scientist who worked at Bell Labs alongside Unix creators Ken Thompson and Dennis Ritchie and contributed greatly to Unix and its school of thought. ... In computer science, a type system defines how a programming language classifies values and expressions into types, how it can manipulate those types and how they interact. ... Look up Implementation in Wiktionary, the free dictionary. ... A dialect of a programming language is a (relatively small) variation or extension of the language that does not change its intrinsic nature. ... C is a general-purpose, block structured, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system. ... SNOBOL (StriNg Oriented symBOlic Language) is a computer programming language developed between 1962 and 1967 at AT&T Bell Laboratories by David J. Farber, Ralph E. Griswold and Ivan P. Polonsky. ... The Bourne shell, or sh, was the default Unix shell of Unix Version 7, and replaced the Thompson shell, whose executable file had the same name, sh. ... Wikibooks has a book on the topic of Perl Programming Perl is a dynamic programming language created by Larry Wall and first released in 1987. ... The Korn shell (ksh) is a Unix shell which was developed by David Korn (AT&T Bell Laboratories) in the early 1980s. ... The syntax of JavaScript is a set of rules that defines how a JavaScript program will be written and interpreted. ... An operating system (OS) is a software that manages computer resources and provides programmers with an interface used to access those resources. ... A cross-platform (or platform independent) programming language, software application or hardware device works on more than one system platform (e. ... A website (alternatively, Web site or web site) is a collection of Web pages, images, videos or other digital assets that is hosted on one or several Web server(s), usually accessible via the Internet, cell phone or a LAN. A Web page is a document, typically written in HTML... A programming language is an artificial language that can be used to control the behavior of a machine, particularly a computer. ... Last name redirects here. ... Dr. Alfred V. Aho is a computer scientist. ... Peter J. Weinberger is a computer scientist who worked at AT&T Bell Labs and contributed to the design of the pioneering AWK programming language (he is the W in AWK). ... Brian Wilson Kernighan (IPA pronunciation: , the g is silent), (born 1942 in Toronto, Ontario, Canada) is a computer scientist who worked at Bell Labs alongside Unix creators Ken Thompson and Dennis Ritchie and contributed greatly to Unix and its school of thought. ... Genera Uria Alle Alca Pinguinus Synthliboramphus Cepphus Brachyramphus Ptychoramphus Aethia Cerorhinca Fratercula Extinct genera, see Systematics Auks are birds of the family Alcidae in the order Charadriiformes. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIXÂ®, sometimes also written as or Â® with small caps) 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. ... Plan 9 from Bell Labs is a distributed operating system, primarily used as a research vehicle. ...

AWK is an example of a programming language that extensively uses the string datatype, associative arrays (that is, arrays indexed by key strings), and regular expressions. The power, terseness, and limitations of AWK programs and sed scripts inspired Larry Wall to write Perl. Because of their dense notation, all these languages are often used for writing one-liner programs. A programming language is an artificial language that can be used to control the behavior of a machine, particularly a computer. ... In computer programming and formal language theory, (and other branches of mathematics), a string is an ordered sequence of symbols. ... In computer science, a datatype or data type (often simply a type) is a name or label for a set of values and some operations which one can perform on that set of values. ... An associative array (also map, hash, dictionary, finite map, lookup table, and in query-processing an index or index file) is an abstract data type composed of a collection of keys and a collection of values, where each key is associated with one value. ... In computing, a regular expression is a string that is used to describe or match a set of strings, according to certain syntax rules. ... The correct title of this article is . ... Larry Wall Larry Wall (born September 27, 1954) is a programmer, linguist, and author, most widely known for his creation of the Perl programming language in 1987. ... Wikibooks has a book on the topic of Perl Programming Perl is a dynamic programming language created by Larry Wall and first released in 1987. ... A one-liner is a computer program or expression that takes no more than a single line. ...

AWK is one of the early tools to appear in Version 7 Unix and gained popularity as a way to add computational features to a Unix pipeline. A version of the AWK language is a standard feature of nearly every modern Unix-like operating system available today. AWK is mentioned in the Single UNIX Specification as one of the mandatory utilities of a Unix operating system. Besides the Bourne shell, AWK is the only other scripting language available in a standard Unix environment. Implementations of AWK exist as installed software for almost all other operating systems. Seventh Edition Unix, also called Version 7 Unix, Version 7 or just V7, was an important early release of the Unix operating system. ... Diagram of the relationships between several Unix-like systems A 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. ... An operating system (OS) is a software that manages computer resources and provides programmers with an interface used to access those resources. ... The Single UNIX Specification (SUS) is the collective name of a family of standards for computer operating systems to qualify for the name Unix. The SUS is developed and maintained by the Austin Group, based on earlier work by the IEEE and The Open Group. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIXÂ®, sometimes also written as or Â® with small caps) 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. ... An operating system (OS) is a software that manages computer resources and provides programmers with an interface used to access those resources. ... The Bourne shell, or sh, was the default Unix shell of Unix Version 7, and replaced the Thompson shell, whose executable file had the same name, sh. ...

Structure of AWK programs

pairs, where pattern is typically an expression and action is a series of commands. Each line of input is tested against all the patterns in turn and the action executed if the expression is true. Either the pattern or the action may be omitted. The pattern defaults to matching every line of input. The default action is to print the line of input.

In addition to a simple AWK expression, the pattern can be BEGIN or END causing the action to be executed before or after all lines of input have been read, or pattern1, pattern2 which matches the range of lines of input starting with a line that matches pattern1 up to and including the line that matches pattern2 before again trying to match against pattern1 on future lines.

In addition to normal arithmetic and logical operators, AWK expressions include the tilde operator, ~, which matches a regular expression against a string. As a handy default, /regexp/ without using the tilde operator matches against the current line of input. In computing, a regular expression is a string that is used to describe or match a set of strings, according to certain syntax rules. ...

AWK commands

AWK commands are the statement that is substituted for action in the examples above. AWK commands can include function calls, variable assignments, calculations, or any combination thereof. AWK contains built-in support for many functions; many more are provided by the various flavors of AWK. Also, some flavors support the inclusion of dynamically linked libraries, which can also provide more functions. In computer science, a library is a collection of subprograms used to develop software. ...

For brevity, the enclosing curly braces ( { } ) will be omitted from these examples.

The print command

The print command is used to output text. The output text is always terminated with a predefined string called the output record separator (ORS) whose default value is a newline. The simplest form of this command is:

This displays the contents of the current line. In AWK, lines are broken down into fields, and these can be displayed separately:

Although these fields ($X) may bear resemblance to variables (the $ symbol indicates variables in perl), they actually refer to the fields of the current line. A special case, $0, refers to the entire line. In fact, the commands "print" and "print $0" are identical in functionality.

The print command can also display the results of calculations and/or function calls:

Variables and Syntax

Variable names can use any of the characters [A-Za-z0-9_], with the exception of language keywords. The operators + - * / represent addition, subtraction, multiplication, and division, respectively. For string concatenation, simply place two variables (or string constants) next to each other. It is optional to use a space in between if string constants are involved. But you can't place two variable names adjacent to each other without having a space in between. String constants are delimited by double quotes. Statements need not end with semicolons. Finally, comments can be added to programs by using # as the first character on a line. This article is about the string operation of computer programming. ... Delimited data uses specific characters (delimiters) to separate its values. ...

User-defined functions

In a format similar to C, function definitions consist of the keyword function, the function name, argument names and the function body. Here is an example of a function. C is a general-purpose, block structured, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system. ...

Functions can have variables that are in the local scope. The names of these are added to the end of the argument list, though values for these should be omitted when calling the function. It is convention to add some whitespace in the argument list before the local variables, in order to indicate where the parameters end and the local variables begin. For information on the programming language Whitespace, see Whitespace programming language. ...

Sample applications

Hello World

Here is the ubiquitous "Hello world program" program written in AWK: A hello world program is a computer program that prints out Hello, World! on a display device. ...

Note that you do not need an explicit exit statement, as if the only pattern is BEGIN, no command-line arguments are processed.

Print lines longer than 80 characters

Print all lines longer than 80 characters. Note that the default action is to print the current line.

The AWK Programming Language now specifies an explicit $0 in the length function:

Print a count of words

Count words in the input, and print lines, words, and characters (like wc) wc (short for word count) is a command in Unix-like operating systems. ...

As there is no pattern for the first line of the program, every line of input matches by default so the increment actions are executed for every line. Note that w += NF is shorthand for w = w + NF.

Sum last word

s is incremented by the numeric value of $NF which is the last word on the line as defined by AWK's field separator, by default white-space. NF is the number of fields in the current line, e.g. 4. Since $4 is the value of the fourth field, $NF is the value of the last field in the line regardless of how many fields this line has, or whether it has more or fewer fields than surrounding lines. $ is actually a unary operator with the highest operator precedence. (If the line has no fields then NF is 0, $0 is the whole line, which in this case is empty apart from possible white-space, and so has the numeric value 0.) This article is about the concept of operator precedence. ...

At the end of the input the END pattern matches so s is printed. However, since there may have been no lines of input at all, in which case no value has ever been assigned to s, it will by default be an empty string. Adding zero to a variable is an AWK idiom for coercing it from a string to a numeric value. (Concatenating an empty string is to coerce from a number to a string, e.g. s "". Note, there's no operator to concatenate strings, they're just placed adjacently.) With the coercion the program prints 0 on an empty input, without it an empty line is printed.

Match a range of input lines

The yes command repeatedly prints the letter "y" on a line. In this case, we tell the command to print the word "Wikipedia". The action statement prints each line numbered. The printf function emulates the standard C printf. The pattern to match, however, works as follows: NR is the number of records, typically lines of input, AWK has so far read, i.e. the current line number, starting at 1 for the first line of input. % is the modulo operator. NR % 4 == 1 is true for the first, fifth, ninth, etc., lines of input. Likewise, NR % 4 == 3 is true for the third, seventh, eleventh, etc., lines of input. The range pattern is false until the first part matches, on line 1, and then remains true up to and including when the second part matches, on line 3. It then stays false until the first part matches again on line 5. The sed command is used to print the first 7 lines, to prevent yes running forever. It is equivalent to head -7 if the head command is available. yes is a Unix command, which outputs an affirmative response, or a user-defined string of text continuously until killed. ... Several programming languages implement a printf function, to output a formatted string. ... The word modulo (Latin, with respect to a modulus of ___) is the Latin ablative of modulus which itself means a small measure. ... The correct title of this article is . ... head is a program that shows the first 10 lines by default of a file or piped data, on Unix and Unix-like systems. ...

The first part of a range pattern being constantly true, e.g. 1, can be used to start the range at the beginning of input. Similarly, if the second part is constantly false, e.g. 0, the range continues until the end of input:

prints lines of input from the first line matching the regular expression ^--cut here--$, that is, a line containing only the phrase "---cut here---", to the end.

Calculate word frequencies

Word frequency, uses associative arrays: An associative array (also map, hash, dictionary, finite map, lookup table, and in query-processing an index or index file) is an abstract data type composed of a collection of keys and a collection of values, where each key is associated with one value. ...

The BEGIN block sets the field separator to any sequence of non-alphabetic characters. Note that separators can be regular expressions. After that, we get to a bare action, which performs the action on every input line. In this case, for every field on the line, we add one to the number of times that word, first converted to lowercase, appears. Finally, in the END block, we print the words with their frequencies. The line

creates a loop that goes through the array words, setting i to each subscript of the array. This is different from most languages, where such a loop goes through each value in the array. This means that you print the word with each count in a simple way. tolower was an addition to the One True awk (see below) made after the book was published.

Match pattern from command line

This program can be represented in several ways. The first one uses the Bourne shell to make a shell script that does everything. It is the shortest of these methods: The Bourne shell, or sh, was the default Unix shell of Unix Version 7, and replaced the Thompson shell, whose executable file had the same name, sh. ...

The $pattern in the awk command is not protected by quotes. The ~ operator sees if a string matches a pattern, equivalently the !~ operator sees if it does not. FILENAME contains the current filename. awk has no explicit concatenation operator; two adjacent strings concatenate them. $0 expands to the original unchanged input line.

There are alternate ways of writing this. This shell script accesses the environment directly from within awk:

This is a shell script that uses ENVIRON, an array introduced in a newer version of the One True awk after the book was published. The subscript of ENVIRON is the name of an environment variable; its result is the variable's value. This is like the getenv function in various standard libraries and POSIX. The shell script makes an environment variable pattern containing the first argument, then drops that argument and has awk look for the pattern in each file. POSIX or Portable Operating System Interface[1] is the collective name of a family of related standards specified by the IEEE to define the application programming interface (API) for software compatible with variants of the Unix operating system. ...

The next way uses command-line variable assignment, in which an argument to awk can be seen as an assignment to a variable:

Finally, this is written in pure awk, without help from a shell or without the need to know too much about the implementation of the awk script (as the variable assignment on command line one does), but is a bit lengthy:

The BEGIN is necessary not only to extract the first argument, but also to prevent it from being interpreted as a filename after the BEGIN block ends. ARGC, the number of arguments, is always guaranteed to be 1, as ARGV[0] is the name of the command that executed the script, most often the string "awk". Also note that ARGV[ARGC] is the empty string, "". # initiates a comment that expands to the end of the line.

Self-contained AWK scripts

As with many other programming languages, self-contained AWK script can be constructed using the so-called "shebang" syntax. For other uses, see Shebang. ...

For example, a UNIX command called hello.awk that prints the string "Hello, world!" may be built by creating a file named hello.awk containing the following lines:

The -f tells awk that the argument that follows is the file to read the awk program from, which is placed there by the shell when running.

AWK versions and implementations

AWK was originally written in 1977, and distributed with Version 7 Unix. Seventh Edition Unix, also called Version 7 Unix, Version 7 or just V7, was an important early release of the Unix operating system. ...

In 1985 its authors started expanding the language, most significantly by adding user-defined functions. The language is described in the book The AWK Programming Language, published 1988, and its implementation was made available in releases of UNIX System V. To avoid confusion with the incompatible older version, this version was sometimes known as "new awk" or nawk. This implementation was released under a free software license in 1996, and is still maintained by Brian Kernighan. (see external links below) It has been suggested that Traditional Unix be merged into this article or section. ... Free software is software which grants recipients the freedom to modify and redistribute the software. ...

BWK awk refers to the version by Brian W. Kernighan. It has been dubbed the "One True AWK" because of the use of the term in association with the book^[1] that originally described the language, and the fact that Kernighan was one of the original authors of awk. FreeBSD refers to this version as one-true-awk^[2]. This version also has features not in the book, such as toupper and ENVIRON that are not in the original book; see the FIXES file in the source archive for details. Brian Wilson Kernighan (IPA pronunciation: , the g is silent), (born 1942 in Toronto, Ontario, Canada) is a computer scientist who worked at Bell Labs alongside Unix creators Ken Thompson and Dennis Ritchie and contributed greatly to Unix and its school of thought. ...

gawk (GNU awk) is another free software implementation. It was written before the original implementation became freely available, and is still widely used. Many Linux distributions come with a recent version of gawk and gawk is widely recognized as the de-facto standard implementation in the Linux world; gawk version 3.0 was included as awk in FreeBSD prior to version 5.0. Subsequent versions of FreeBSD use BWK awk in order to avoid^[3] the GPL, a more restrictive (in the sense that GPL licensed code cannot be modified to become proprietary software) license than the BSD license. ^[4] GNU (pronounced ) is a computer operating system composed entirely of free software. ... A Linux distribution, often simply distribution or distro, is a member of the Linux family of Unix-like operating systems comprising the Linux kernel, the non-kernel parts of the GNU operating system, and assorted other software. ... This article is about operating systems that use the Linux kernel. ... FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ... GPL redirects here. ... This article or section may contain original research or unverified claims. ... The BSD daemon BSD licenses represent a family of permissive free software licenses. ...

xgawk is a SourceForge project^[5] based on gawk. It extends gawk with dynamically loadable libraries.

mawk is a very fast AWK implementation by Mike Brennan based on a byte code interpreter. It has been suggested that this article or section be merged with Managed code. ...

awka (whose front end is written on top of the mawk program) is a translator of awk scripts into C code. When compiled, statically including the author's libawka.a, the resulting executables are considerably sped up and according to the author's tests compare very well with other versions of awk, perl or tcl. Small scripts will turn into programs of 160-170 kB. http://awka.sourceforge.net

Downloads and further information about these versions are available from the sites listed below.

Thompson AWK or TAWK is an AWK compiler for DOS and Windows, previously sold by Thompson Automation Software (which has ceased its activities). A diagram of the operation of a typical multi-language, multi-target compiler. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... Windows redirects here. ...

Jawk is a SourceForge project^[6] to implement AWK in Java. Extensions to the language are added to provide access to Java features within AWK scripts (i.e., Java threads, sockets, Collections, etc). Java language redirects here. ... Java language redirects here. ...

BusyBox includes a sparsely documented Awk implementation that appears to be complete, written by Dmitry Zakharov. This implementation is the smallest Awk implementation out there, suitable for embedded systems. BusyBox is a software application which provides many standard Unix tools, much like the larger (but more capable) GNU Core Utilities. ...

Books

Dr. Alfred V. Aho is a computer scientist. ... Brian Kernighan¹ (born 1942) is a computer scientist who worked at the Bell Labs and contributed to the design of the pioneering AWK and AMPL programming languages. ... Peter J. Weinberger is a computer scientist who worked at AT&T Bell Labs and contributed to the design of the pioneering AWK programming language (he is the W in AWK). ... Dale Dougherty is one of the co-founders (with Tim OReilly) of OReilly Media. ... Programming Perl is a classic OReilly book. ...

References

See also

External links

The Single UNIX Specification (SUS) is the collective name of a family of standards for computer operating systems to qualify for the name Unix. The SUS is developed and maintained by the Austin Group, based on earlier work by the IEEE and The Open Group. ... This article or section reads like an advertisement. ... Brian Wilson Kernighan (IPA pronunciation: , the g is silent), (born 1942 in Toronto, Ontario, Canada) is a computer scientist who worked at Bell Labs alongside Unix creators Ken Thompson and Dennis Ritchie and contributed greatly to Unix and its school of thought. ... Princeton University is a private coeducational research university located in Princeton, New Jersey. ... Usenet (USEr NETwork) is a global, decentralized, distributed Internet discussion system that evolved from a general purpose UUCP architecture of the same name. ... A newsgroup is a repository usually within the Usenet system, for messages posted from many users at different locations. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIXÂ®, sometimes also written as or Â® with small caps) 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. ... A command line interface or CLI is a method of interacting with a computer by giving it lines of textual commands (that is, a sequence of characters) either from keyboard input or from a script. ... This is a list of UNIX utilities as specified by IEEE Std 1003. ... The title given to this article is incorrect due to technical limitations. ... chattr is a UNIX program that allows a user to set certain attributes to a file. ... This article does not cite any references or sources. ... The chmod command (abbreviated from change mode) is a shell command in Unix and Unix-like environments. ... chown is a Unix command used to change the recorded owner of a computer file. ... The chgrp command is used by unprivileged users on Unix-like systems to change the group associated with a file. ... 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. ... cmp is a command line utility for computer systems that use a Unix operating system. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... 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. ... 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 is usually implemented by reading the mtab file or using statfs. ... file is a program originated in Unix that runs under the shell (command-line) to determine the file type heuristically instead of other simpler ways to classify it, like with file extensions, MIMEs, etc. ... The system utility fsck (for file system check or file system consistency check) is a tool for checking the consistency of a file system in the Unix system and clones thereof. ... fuser is a UNIX command showing which processes are using a specified file. ... The ln command is used on Unix-like systems to create links between files. ... For other uses, see LS. ls is a command specified by POSIX and the Single UNIX Specification, and is thus implemented in Unix and Unix-like operating systems. ... lsof is a command found in almost any Unix system that reports open files by processes of a Operating System. ... The mkdir command in the Unix operating system is used to make a new directory. ... ... The correct title of this article is . ... The title given to this article is incorrect due to technical limitations. ... The title given to this article is incorrect due to technical limitations. ... This article does not cite any references or sources. ... split is a Unix utility most commonly used to split a file into one or more other files. ... touch is a standard Unix program used to change a files access and modification timestamps. ... The at command is used to schedule commands to be executed once at a particular time in the future. ... A chroot on Unix operating systems is an operation which changes the root directory. ... In computing, cron is a time-based scheduling service in Unix-like computer operating systems. ... Exit is a command used in many operating systems command line shells. ... Wikibooks has more about this subject: kill In Unix and Unix-like operating systems, kill is a command used to send simple messages to processes running on the system. ... killall is a command line utility initially written for use with the GNU/Linux operating systems. ... nice (IPA pronunciation: ) is a command found on UNIX and other POSIX-like operating systems such as Linux. ... pgrep is a command line utility initially written for use with the Solaris 7 operating systems and then ported to GNU/Linux. ... pidof is a Linux utility that returns the process ID (PID) of a running process. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... pstree is a Unix command that shows the running processes as a tree. ... sleep is an instruction for a computer that delays execution for a specified period of time. ... This article is about a Unix command. ... In most Unix-like operating systems, the top command produces a frequently-updated list of processes. ... The correct title of this article is . ... In Unix, watch runs the specified command repeatedly and displays the output on stdout so you can watch it change over time. ... env is a shell utility for Unix-like operating systems (including Linux). ... In computer networking, the Name/Finger protocol and the Finger user information protocol are simple network protocols for the exchange of human-oriented status and user information. ... In computer software, id is a program in Unix operating systems that prints the uid of the account of which the program is executed by. ... Usage: logname [OPTION] Print the name of the current user. ... mesg is a Unix command that sets or reports the permission other users have to write to your terminal using the talk and write commands. ... passwd is a tool on most Unix and Linux systems used to change a users password. ... The Unix su (substitute user or switch user or super user) command is used to assume the login shell of another user without logging out. ... This article is about the Unix command line program. ... In computer software, uname is a program in Unix operating systems that prints the name, version and other details about the running operating system. ... Uptime is a measure of the time a computer system has been up and running. ... The command w on many Unix-like operating systems provides a quick summary of every user logged into a computer, what that user is currently doing, and what load all the activity is imposing on the computer itself. ... wall is a Unix command line utility. ... who is a Unix-command which creates almost the same output as the Unix-command w; it shows you users currently logged in a system. ... write can refer to several Unix commands. ... AWK is a general purpose computer language that is designed for processing text-based data, either in files or data streams. ... The comm command in Unix is a utility that is used to compare two files. ... cut is a Unix command which is typically used to extract a certain range of characters from a line, usually from a file. ... ed was the original standard text editor on the Unix operating system. ... ex, short for EXtended, is a line editor for Unix systems. ... Usage: fmt [-DIGITS] [OPTION]... [FILE]... Reformat each paragraph in the FILE(s), writing to standard output. ... head is a program that shows the first 10 lines by default of a file or piped data, on Unix and Unix-like systems. ... iconv is a computer program and a standardized API used to convert between different character encodings. ... join is a command in Unix-like operating systems. ... less is a program on Unix and Unix-like systems used to view (but not change) the contents of a text file one screen at a time. ... Example output of the more command. ... Paste is a Unix utility tool which is used to join files horizontally (parallel merging), e. ... The correct title of this article is . ... sort is a standard Unix command line program that prints the lines of its input in sorted order. ... Usage: tac [OPTION]... [FILE]... Write each FILE to standard output, last line first. ... tail is a program on Unix and Unix-like systems used to display the last few lines of a text file or piped data. ... tr (abbreviated from translate or transliterate) is a command in Unix-like operating systems. ... uniq is a Unix utility which, when fed a text file, outputs the file with adjacent identical lines collapsed to one. ... wc (short for word count) is a command in Unix-like operating systems. ... xargs is a command of the Unix and most Unix-like operating system which eases passing command output to another command as command line arguments. ... In computing, a shell is a piece of software that provides an interface for users (command line interpreter). ... In Unix shells (like csh, bash, etc. ... basename is a common program found on Unix systems; typically it is the GNU Projects coreutils version, which is Free software. ... echo is a command in Unix (and by extension, its descendants, such as Linux) and MS-DOS that places a string on the terminal. ... expr is a command line Unix utility which evaluates an expression and outputs the corresponding value. ... In Unix-like operating systems, false is the command that always returns the value 1, which is regarded by the shell as the logical value false. ... Several programming languages implement a printf function, to output a formatted string. ... test is a Unix command that evaluates conditional expressions. ... In Unix-like operating systems, true is a command whose only function is to always return the value 0, which is regarded by the shell as the logical value true. ... unset is a Unix shell command. ... inetd is a daemon on many Unix systems that manages Internet services. ... This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... For other uses, see Ping (disambiguation). ... In computing, rlogin is a Unix software utility that allows users to log in on another host via a network, communicating via TCP port 513. ... In computing, netcat is a network utility for reading from and writing to network connections on either TCP or UDP. It is designed in a thin and simple way, which makes it easy to incorporate in larger applications. ... traceroute outputs the list of traversed routers in simple text format, together with timing information traceroute is a computer network tool used to determine the route taken by packets across an IP network. ... For other uses, see Find (disambiguation). ... grep is a command line utility that was originally written for use with the Unix operating system. ... In computer software, strings is a program in Unix-like operating systems that prints the strings found in an executable. ... The banner program displays a large ASCII art version of input text. ... bc is an arbitrary precision calculator language with syntax similar to the C programming language. ... cal is a standard program on Unix that prints an ASCII calendar of the given month or year. ... Clear being used on GNU/LInux under uxterm This article or section does not adequately cite its references or sources. ... The title given to this article is incorrect due to technical limitations. ... dd is a common UNIX program whose primary purpose is the low-level copying and conversion of raw data. ... The Common Unix Printing System (CUPS) is a modularised computer printing system for Unix-like operating systems that allows computers to act as powerful print servers. ... The man page on man Almost all substantial UNIX and Unix-like operating systems have extensive documentation known as man pages (short for manual pages). The Unix command used to display them is man. ... size is a command line utility originally written for use with the Unix-like operating systems. ... yes is a Unix command, which outputs an affirmative response, or a user-defined string of text continuously until killed. ...

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