nl
NL(1) General Commands Manual NL(1)
NAME
nl – line numbering filter
SYNOPSIS
nl [-p] [-b type] [-d delim] [-f type] [-h type] [-i incr] [-l num]
[-n format] [-s sep] [-v startnum] [-w width] [file]
DESCRIPTION
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 standard output.
The nl utility treats the text it reads in terms of logical pages. Unless
specified otherwise, 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 signalled by input lines containing
nothing but one of the following sequences of delimiter characters:
Line Start of
\:\:\: header
\:\: body
\: footer
If the input does not contain any logical page section signalling
directives, the text being read is assumed to consist of a single logical
page body.
The following options are available:
-b type 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 specified by expr.
The default type for logical page body lines is t.
-d delim Specify the delimiter characters used to indicate the
start of a logical page section in the input file. At
most two characters may be specified; if only one
character is specified, the first character is replaced
and the second character remains unchanged. The default
delim characters are “\:”.
-f type Specify the same as -b type except for logical page
footer lines. The default type for logical page footer
lines is n.
-h type Specify the same as -b type except for logical page
header lines. The default type for logical page header
lines is n.
-i incr 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.
-n format 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.
-v startnum Specify the initial value used to number logical page
lines; see also the description of the -p option. The
default startnum value is 1.
-w width 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.
ENVIRONMENT
The LANG, LC_ALL, LC_CTYPE and LC_COLLATE environment variables affect the
execution of nl as described in environ(7).
EXIT STATUS
The nl utility exits 0 on success, and >0 if an error occurs.
SEE ALSO
jot(1), pr(1)
STANDARDS
The nl utility conforms to IEEE Std 1003.1-2001 (“POSIX.1”).
HISTORY
The nl utility first appeared in AT&T System V Release 2 UNIX.
BUGS
Input lines are limited to LINE_MAX (2048) bytes in length.
macOS 12.1 January 26, 2005 macOS 12.1