NL(1P) POSIX Programmer's Manual NL(1P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAMEnl — line numbering filter
SYNOPSISnl [−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 shall read lines from the named file or the standard
input if no file is named and shall reproduce the lines to standard
output. Lines shall be numbered on the left. Additional functionality
may be provided in accordance with the command options in effect.
The nl utility views the text it reads in terms of logical pages. Line
numbering shall be 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 (for example, no numbering of header and
footer lines while numbering blank lines only in the body).
The starts of logical page sections shall be signaled by input lines
containing nothing but the following delimiter characters:
┌───────────┬────────────┐
│ Line │ Start of │
├───────────┼────────────┤
│\:\:\: │ Header │
│\:\: │ Body │
│\: │ Footer │
└───────────┴────────────┘
Unless otherwise specified, nl shall assume the text being read is in a
single logical page body.
OPTIONS
The nl utility shall conform to the Base Definitions volume of
POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines. Only one file
can be named.
The following options shall be supported:
−b type Specify which logical page body lines shall be numbered. Rec‐
ognized types and their meaning are:
a Number all lines.
t Number only non-empty lines.
n No line numbering.
pstring Number only lines that contain the basic regular
expression specified in string.
The default type for logical page body shall be t (text lines
numbered).
−d delim Specify the delimiter characters that indicate the start of a
logical page section. These can be changed from the default
characters "\:" to two user-specified characters. If only one
character is entered, the second character shall remain the
default character ':'.
−f type Specify the same as b type except for footer. The default for
logical page footer shall be n (no lines numbered).
−h type Specify the same as b type except for header. The default
type for logical page header shall be n (no lines numbered).
−i incr Specify the increment value used to number logical page
lines. The default shall be 1.
−l num Specify the number of blank lines to be considered as one.
For example, −l 2 results in only the second adjacent blank
line being numbered (if the appropriate −h a, −b a, or −f a
option is set). The default shall be 1.
−n format Specify the line numbering format. Recognized values are: ln,
left justified, leading zeros suppressed; rn, right justi‐
fied, leading zeros suppressed; rz, right justified, leading
zeros kept. The default format shall be rn (right justified).
−p Specify that 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 shall be a
<tab>.
−v startnum
Specify the initial value used to number logical page lines.
The default shall be 1.
−w width Specify the number of characters to be used for the line num‐
ber. The default width shall be 6.
OPERANDS
The following operand shall be supported:
file A pathname of a text file to be line-numbered.
STDIN
The standard input shall be used if no file operand is specified, and
shall be used if the file operand is '−' and the implementation treats
the '−' as meaning standard input. Otherwise, the standard input shall
not be used. See the INPUT FILES section.
INPUT FILES
The input file shall be a text file.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of nl:
LANG Provide a default value for the internationalization vari‐
ables that are unset or null. (See the Base Definitions vol‐
ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
ables for the precedence of internationalization variables
used to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of
all the other internationalization variables.
LC_COLLATE
Determine the locale for the behavior of ranges, equivalence
classes, and multi-character collating elements within regu‐
lar expressions.
LC_CTYPE Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments and input
files), the behavior of character classes within regular
expressions, and for deciding which characters are in charac‐
ter class graph (for the −b t, −f t, and −h t options).
LC_MESSAGES
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard
error.
NLSPATH Determine the location of message catalogs for the processing
of LC_MESSAGES.
ASYNCHRONOUS EVENTS
Default.
STDOUT
The standard output shall be a text file in the following format:
"%s%s%s", <line number>, <separator>, <input line>
where <line number> is one of the following numeric formats:
%6d When the rn format is used (the default; see −n).
%06d When the rz format is used.
%−6d When the ln format is used.
<empty> When line numbers are suppressed for a portion of the page;
the <separator> is also suppressed.
In the preceding list, the number 6 is the default width; the −w option
can change this value.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
In using the −d delim option, care should be taken to escape characters
that have special meaning to the command interpreter.
EXAMPLES
The command:
nl −v 10 −i 10 −d \!+ file1
numbers file1 starting at line number 10 with an increment of 10. The
logical page delimiter is "!+". Note that the '!' has to be escaped
when using csh as a command interpreter because of its history substi‐
tution syntax. For ksh and sh the escape is not necessary, but does
not do any harm.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
pr
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
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IEEE/The Open Group 2013 NL(1P)
