View source for Head (Unix)

{{more citations needed|date=June 2020}}
{{short description|Program on Unix and Unix-like systems}}
{{lowercase}}
{{Infobox software
| name                   = head
| logo                   = 
| screenshot             = Head-example-command.gif
| screenshot size        = 
| caption                = Example usage of <code>head</code> command to display first 5 lines of [[Lorem ipsum]] in the specified file 
| author                 = 
| developer              = Various [[open-source software|open-source]] and [[commercial software|commercial]] developers
| released               = 
| latest release version = 
| latest release date    = 
| operating system       = [[Unix]], [[Unix-like]], [[MSX-DOS]], [[IBM i]]
| platform               = [[Cross-platform]]
| genre                  = [[Command (computing)|Command]]
| license                = [[coreutils]]: [[GPLv3]]
| website                = 
}}
'''{{code|head}}''' is a [[Computer program|program]] on [[Unix]] and [[Unix-like]] [[operating system]]s used to display the beginning  of a text [[Computer file|file]] or [[pipe (computing)|pipe]]d data.

==Syntax==
The command [[syntax]] is:

 head [options] {{angbr|file_name}}

By default, {{tt|head}} will print the first 10 lines of its input to the [[standard output]]. 

===Option flags===

{{glossary}}
{{term|1=-n|2={{tt|-n}} {{angbr|count}}}}
{{term|1=--lines|2={{tt|--lines}}={{angbr|count}}}}
{{defn|1=
The number of lines printed may be changed with a [[command line]] option. The following example shows the first 20 lines of ''filename'':

{{pre|head -n 20 ''filename''}}

This displays the first 5 lines of all files starting with ''foo'':

{{pre|head -n 5 ''foo*''}}

Most versions{{citation needed|date=June 2020}} allow omitting <code>n</code> and instead directly specifying the number: <code>-5</code>. [[GNU]] head allows negative arguments for the <code>-n</code> option, meaning to print all but the last - argument value counted - lines of each input file.
}}
{{term|1=-c|2={{tt|-c}} {{angbr|bytes}}}}
{{term|1=--bytes|2={{tt|--bytes}}={{angbr|bytes}}}}
{{defn|Print first x number of bytes.}}
{{glossary end}}

==Other command==
Many early versions of Unix and Plan 9 did not have this command, and documentation and books used [[sed]] instead:

 sed 5q ''filename''

The example prints every line (implicit) and quits after the fifth.

Equivalently, [[awk]] may be used to print the first five lines in a file:

 awk 'NR < 6' ''filename''

However, neither sed nor awk were available in early versions of [[BSD]], which were based on
[[Version 6 Unix]], and included head.<ref>{{cite journal |last1=Spinellis |first1=Diomidis
|title=dspinellis/unix-history-man: Version 1.0 web pages (v1.1-web)
|journal=Zenodo |date=2022 |doi=10.5281/zenodo.7248228
|url=https://dspinellis.github.io/unix-history-man/man1.html}}</ref>

==Implementations==
A <code>head</code> command is also part of [[ASCII Corporation|ASCII]]'s ''MSX-DOS2 Tools'' for [[MSX-DOS]] version 2.<ref>[https://archive.org/details/MSXDOS2TOOLS MSX-DOS2 Tools User's Manual by ASCII Corporation]</ref> The {{Mono|head}} command has also been ported to the [[IBM i]] operating system.<ref>{{cite web |title=IBM System i Version 7.2 Programming Qshell |language=en |author=IBM |author-link=IBM |url=https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_74/rzahz/rzahzpdf.pdf?view=kc |access-date=2020-09-05 }}</ref>

==See also==
*[[tail (Unix)]]
*[[dd (Unix)]]
*[[List of Unix commands]]

==References==
{{Reflist}}

==External links==
{{Wikibooks|Guide to Unix|Commands}}
*[https://www.gnu.org/software/coreutils/manual/html_node/head-invocation.html head] manual page from [[GNU]] [[coreutils]].
*[http://www.freebsd.org/cgi/man.cgi?query=head&apropos=0&sektion=0&manpath=FreeBSD+5.3-RELEASE+and+Ports&format=html FreeBSD documentation for head]

{{Unix commands}}
{{Core Utilities commands}}

[[Category:Unix text processing utilities]]
[[Category:Unix SUS2008 utilities]]
[[Category:IBM i Qshell commands]]