Nl (Unix) Explained

nl
Operating System:	Unix and Unix-like
Platform:	Cross-platform
Genre:	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

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. It first appeared in System V release 2.

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

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.^[1]

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 doneThe 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 strawberryIt can be useful as an alternative to :$ cat somefileaaaabbbbccccdddc$ nl somefile | grep cccc 3 cccc

See also

• wc (Unix) – the word count command
• cat (Unix) – concatenate command (-n flag is equivalent to nl -a)
• List of Unix commands

Notes and References

1. Web site: Native Win32 ports of some GNU utilities. unxutils.sourceforge.net.