nl
Operating systemUnix and Unix-like
PlatformCross-platform
TypeCommand
Licensecoreutils: GPLv3+

nl is a Unix utility for numbering lines, either from a file or from standard input, reproducing output on standard output.

History

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.[1] It first appeared in System V release 2.[2]

The version of nl bundled in GNU coreutils was written by Scott Bartram and David MacKenzie.[3]

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.[4]

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

 $ nl tf
     1  echo press cr
     2  read cr
     3  done

The following example numbers only the lines that begin with a capital letter A (matching on the regular expression /^A/). filename is optional.

$ nl -b p^A filename
       apple
    1  Apple
       BANANA
    2  Allspice
       strawberry

It can be useful as an alternative to grep -n:

$ cat somefile
aaaa
bbbb
cccc
dddc
$ nl somefile | grep cccc
    3 cccc

See also

References

  1. ↑ nl – Shell and Utilities Reference, The Single UNIX Specification, Version 4 from The Open Group
  2. ↑ nl(1) – FreeBSD General Commands Manual
  3. ↑ nl(1) – Linux General Commands Manual
  4. ↑ "Native Win32 ports of some GNU utilities". unxutils.sourceforge.net.
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