Editing Nl (Unix)

{{Short description|Unix command}}
{{lowercase|nl}}
{{Infobox software
| name                   = nl
| logo                   = 
| screenshot             = 
| screenshot size        = 
| caption                = 
| author                 = 
| developer              = 
| released               = 
| latest release version = 
| latest release date    = 
| operating system       = [[Unix]] and [[Unix-like]]
| platform               = [[Cross-platform]]
| genre                  = [[Command (computing)|Command]]
| license                = [[coreutils]]: [[GPLv3+]]
| website                = 
}}
'''nl''' is a [[Unix utility]] for numbering lines, either from a file or from standard input, reproducing output on standard output.

== History ==
{{code|nl}} is part of the [[X/Open]] Portability Guide since issue 2 of 1987. It was inherited into the first version of POSIX.1 and the [[Single Unix Specification]].<ref>{{man|cu|nl|SUS}}</ref> It first appeared in [[System V]] release 2.<ref>{{man|1|nl|FreeBSD}}</ref>

The version of <code>nl</code> bundled in [[GNU]] [[coreutils]] was written by Scott Bartram and David MacKenzie.<ref>{{man|1|nl|ManKier}}</ref>

The command is available as a separate package for [[Microsoft Windows]] as part of the [[UnxUtils]] collection of [[Native (computing)|native]] [[Windows API|Win32]] [[porting|ports]] of common GNU Unix-like utilities.<ref>{{Cite web|url=http://unxutils.sourceforge.net/|title=Native Win32 ports of some GNU utilities|website=unxutils.sourceforge.net}}</ref>

==Syntax==
The command has a number of switches:

*a - number all lines
*t - number lines with printable text only
*n - no line numbering
*string - number only those lines containing the regular expression defined in the ''string'' supplied.

The default applied switch is ''t''.

nl also supports some command line options.

==Example==
<syntaxhighlight lang="bash">
 $ nl tf
     1  echo press cr
     2  read cr
     3  done
</syntaxhighlight>
The following example numbers only the lines that begin with a capital letter A (matching on the [[regular expression]] /^A/).  ''filename'' is optional.
<syntaxhighlight lang="console">
$ nl -b p^A filename
       apple
    1  Apple
       BANANA
    2  Allspice
       strawberry
</syntaxhighlight>
It can be useful as an alternative to {{mono|[[grep|grep -n]]}}:
<syntaxhighlight lang="console">
$ cat somefile
aaaa
bbbb
cccc
dddc
$ nl somefile | grep cccc
    3 cccc
</syntaxhighlight>

==See also==
*[[wc (Unix)]] – the word count command
*[[cat (Unix)]] – concatenate command (-n flag is equivalent to nl -a)
*[[List of Unix commands]]

==References==
{{Reflist}}

==External links==
{{Wikibooks|Guide to Unix|Commands}}

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

[[Category:Unix text processing utilities]]
[[Category:Unix SUS2008 utilities]]