Nl (Unix)


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.

Syntax

The command has a number of switches:
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. 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