Nl (Unix)

Template:Short description Template:Lowercase Template:Infobox software nl is a Unix utility for numbering lines, either from a file or from standard input, reproducing output on standard output.

History

<syntaxhighlight lang="text" class="" style="" inline="1">nl</syntaxhighlight> 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>Template:Man</ref> It first appeared in System V release 2.<ref>Template:Man</ref>

The version of nl bundled in GNU coreutils was written by Scott Bartram and David MacKenzie.<ref>Template:Man</ref>

The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities.<ref>Template:Cite web</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 Template:Mono: <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