NAME

nl — line numbering filter

SYNOPSIS

[XSI] 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 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 XBD 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. Recognized 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 justified, 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 number. 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 variables that are unset or null. (See XBD 8.2 Internationalization Variables 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 regular 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 character 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 messages objects and message catalogs.

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.

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 substitution syntax. For ksh and sh the escape is not necessary, but does not do any harm.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

pr

XBD 8. Environment Variables, 12.2 Utility Syntax Guidelines

CHANGE HISTORY

First released in Issue 2.

Issue 5

The option [-f type] is added to the SYNOPSIS. The option descriptions are presented in alphabetic order. The description of -bt is changed to "Number only non-empty lines".

Issue 6

The obsolescent behavior allowing the options to be intermingled with the optional file operand is removed.

Issue 7

Austin Group Interpretation 1003.1-2001 #092 is applied.

SD5-XCU-ERN-97 is applied, updating the SYNOPSIS.

Issue 8

Austin Group Defect 1122 is applied, changing the description of NLSPATH .