NL(1)                      POSIX Programmer's Manual                     NL(1)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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 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.1-2017, 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.
                 Recognized types and their meaning are:

                 aa       Number all lines.

                 tt       Number only non-empty lines.

                 nn       No line numbering.

                 pp_s_t_r_i_n_g Number only lines that contain the basic regular
                         expression specified in string.

                 The default type for logical page body shall be tt (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 bb type except for footer. The default for
                 logical page footer shall be nn (no lines numbered).

       -h type   Specify the same as bb type except for header. The default
                 type for logical page header shall be nn (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 22 results in only the second adjacent blank
                 line being numbered (if the appropriate -h aa, -b aa, or -f aa
                 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 the Base Definitions
                 volume of POSIX.1-2017, Section 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 tt, -f tt, and -h tt 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
       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

       The Base Definitions volume of POSIX.1-2017, 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 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  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.opengroup.org/unix/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.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                                NL(1)
