NL(1)			  BSD 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 fil‐
     ter 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 contain‐
     ing 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 direc‐
     tives, 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.  Recog‐
		  nized 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 regu‐
			  lar 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 speci‐
		  fied, the first character is replaced and the second charac‐
		  ter 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 logi‐
		  cal 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 logi‐
		  cal 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.

BSD			       January 26, 2005 			   BSD