NL(1) BSD General Commands Manual NL(1)
nl -- line numbering filter
nl [-p] [-b type] [-d delim] [-f type] [-h type] [-i incr] [-l num] [-n format] [-s sep]
[-v startnum] [-w width] [file]
The nl utility reads lines from the named file or the standard input if the file argument is
omitted, applies a configurable line numbering filter operation and writes the result to the
The nl utility treats the text it reads in terms of logical pages. Unless specified other-
wise, line numbering is reset at the start of each logical page. A logical page consists of
a header, a body and a footer section; empty sections are valid. Different line numbering
options are independently available for header, body and footer sections.
The starts of logical page sections are signaled by input lines containing nothing but one
of the following sequences of delimiter characters:
Line "Start of"
If the input does not contain any logical page section signaling directives, the text being
read is assumed to consist of a single logical page body.
The following options are available:
Specify the logical page body lines to be numbered. Recognized type arguments are:
a Number all lines.
t Number only non-empty lines.
n No line numbering.
pexpr Number only those lines that contain the basic regular expression speci-
fied by expr.
The default type for logical page body lines is t.
Specify the delimiter characters used to indicate the start of a logical page sec-
tion in the input file. At most two characters may be specified; if only one char-
acter is specified, the first character is replaced and the second character remains
unchanged. The default delim characters are ``\:''.
Specify the same as -b type except for logical page footer lines. The default type
for logical page footer lines is n.
Specify the same as -b type except for logical page header lines. The default type
for logical page header lines is n.
Specify the increment value used to number logical page lines. The default incr
value is 1.
-l num If numbering of all lines is specified for the current logical section using the
corresponding -b a, -f a or -h a option, specify the number of adjacent blank lines
to be considered as one. For example, -l 2 results in only the second adjacent
blank line being numbered. The default num value is 1.
Specify the line numbering output format. Recognized format arguments are:
ln Left justified.
rn Right justified, leading zeros suppressed.
rz Right justified, leading zeros kept.
The default format is rn.
-p Specify that line numbering should not be restarted at logical page delimiters.
-s sep Specify the characters used in separating the line number and the corresponding text
line. The default sep setting is a single tab character.
Specify the initial value used to number logical page lines; see also the descrip-
tion of the -p option. The default startnum value is 1.
Specify the number of characters to be occupied by the line number; in case the
width is insufficient to hold the line number, it will be truncated to its width
least significant digits. The default width is 6.
The nl utility exits 0 on success, and >0 if an error occurs.
The nl utility conforms to X/Open Portability Guide Issue 4, Version 2 (``XPG4.2'') with the
exception of not supporting the intermingling of the file operand with the options, which
the standard considers an obsolescent feature to be removed from a further issue.
The nl utility first appeared in AT&T System V Release 2 UNIX.
BSD February 15, 1999 BSD