Nl (Unix)

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. ==Syntax==

The command has a number of switches: • a - number all lines • t - number lines with printable text only • n - no line numbering • pstring - 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 : $ cat somefile aaaa bbbb cccc dddc $ nl -ba somefile | grep cccc 3 cccc ==See also==