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:
Unless otherwise specified, nl shall assume the text being read is in a
single logical page body.
The nl utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
Only one file can be named.
The following options shall be supported:
Specify which logical page body lines shall be numbered.
Recognized types and their meaning are:
Number all lines.
Number only non-empty lines.
No line numbering.
Number only lines that contain the basic
regular expression specified in string.
The default type for logical page body shall be t (text lines
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 ':' .
Specify the same as btype except for footer.
The default for logical page footer shall be n (no lines
Specify the same as btype except for header.
The default type for logical page header shall be n (no
Specify the increment value used to number logical page
lines. The default shall be 1.
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.
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
Specify that numbering should not be restarted at logical
Specify the characters used in separating the line number
and the corresponding text line. The default sep shall be a
Specify the initial value used to number logical page
lines. The default shall be 1.
Specify the number of characters to be used for the line
number. The default width shall be 6.
The following environment variables shall affect the execution of nl:
Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables for the precedence of internationalization variables used to
determine the values of locale categories.)
If set to a non-empty string value, override the values of
all the other internationalization variables.
Determine the locale for the behavior of ranges, equivalence classes, and
multi-character collating elements within regular expressions.
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
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to standard error.
Determine the location of message catalogs for the
processing of LC_MESSAGES.
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.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 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