nl (Unix)

nl
Operating system	Unix and Unix-like
Platform	Cross-platform
Type	Command
License	coreutils: 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

References

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

External links

[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.

[1]

[2]

[3]

[4]

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Categories Standard Unix programs Unix SUS2008 utilities List

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History

Syntax

Example

See also

References

External links