NL(1)                   FreeBSD 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, applies a configurable
     line numbering filter operation, and writes the result to the standard
     output.  If file is a single dash (`-') or absent, nl reads from the
     standard input.

     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.

EXAMPLES

     Number all non-blank lines:

           $ echo -e "This is\n\n\na simple text" | nl
                1  This is

                2  a simple text

     Number all lines including blank ones, with right justified line numbers
     with leading zeroes, starting at 2, with increment of 2 and a custom
     multi-character separator:

           $ echo -e "This\nis\nan\n\n\nexample" | nl -ba -n rz -i2 -s "->" -v2
           000002->This
           000004->is
           000006->an
           000008->
           000010->
           000012->example

     Number lines matching regular expression for an i followed by either m or
     n

           $ echo -e "This is\na simple text\nwith multiple\nlines" | nl -bp'i[mn]'
                   This is
                1  a simple text
                   with multiple
                2  lines

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 III UNIX.

BUGS

     Input lines are limited to LINE_MAX (2048) bytes in length.

FreeBSD 15.1-STABLE-HBSD         July 24, 2022                           NL(1)