Linux nl command

Updated: 03/13/2021 by Computer Hope
nl command

On Unix-like operating systems, the nl command numbers the lines in a file.

This page describes the GNU/Linux version of nl.

Syntax

nl [OPTION]... [FILE]...

Options

-b,
--body-numbering=STYLE		 use STYLE for numbering body lines
-d,
--section-delimiter=CC		 use CC for separating logical pages
-f,
--footer-numbering=STYLE		 use STYLE for numbering footer lines
-h,
--header-numbering=STYLE		 use STYLE for numbering header lines
-i,
--line-increment=NUMBER		 line number increment at each line
-l,
--join-blank-lines=NUMBER		 group of NUMBER empty lines counted as one
-n,
--number-format=FORMAT		 insert line numbers according to FORMAT
-p,
--no-renumber		 do not reset line numbers at logical pages
-s,
--number-separator=STRING		 add STRING after (possible) line number
-v,
--starting-line-number=NUMBER		 first line number on each logical page
-w,
--number-width=NUMBER		 use NUMBER columns for line numbers
--help display help and exit
--version display version information and exit

By default, nl selects -v1 -i1 -l1 -sTAB -w6 -nrn -hn -bt -fn. CC are two delimiter characters for separating logical pages. A missing second character implies a colon (:).

For a backslash (\), two backslashes (\\).

STYLE is one of:

a number all lines
t number only nonempty lines
n number no lines
pBRE number only lines containing a match for the basic regular expression, BRE

FORMAT is one of:

ln left justified, no leading zeros
rn right justified, no leading zeros
rz right justified, leading zeros

Examples

cat list.txt
apples
oranges
potatoes
lemons
garlic
nl list.txt
     1	apples
     2	oranges
     3	potatoes
     4	lemons
     5	garlic

In the example above, we use the cat command to display the contents of list.txt. Then we use nl to number each line and display the result to standard output.

nl list.txt > nlist.txt
cat nlist.txt
     1	apples
     2	oranges
     3	potatoes
     4	lemons
     5	garlic

In the example above, we run the same nl command, but redirect the output to a new file, nlist.txt. Then we use cat to display the results.

wc — Display a count of lines, words, and characters in a file.