nl: Number lines and write files
nl writes each
-’ means standard input), or
standard input if none are given, to standard output, with line numbers
added to some or all of the lines. Synopsis:
nl [option]… [file]…
nl decomposes its input into (logical) page sections;
by default, the line number is reset to 1 at each logical page section.
nl treats all of the input files as a single document;
it does not reset line numbers or logical pages between files.
A logical page consists of three sections: header, body, and footer. Any of the sections can be empty. Each can be numbered in a different style from the others.
The beginnings of the sections of logical pages are indicated in the input file by a line containing exactly one of these delimiter strings:
The two characters from which these strings are made can be changed from
\’ and ‘
:’ via options (see below), but the pattern and
length of each string cannot be changed.
A section delimiter is replaced by an empty line on output. Any text
that comes before the first section delimiter string in the input file
is considered to be part of a body section, so
nl treats a
file that contains no section delimiters as a single body section.
The program accepts the following options. Also see Common options.
Select the numbering style for lines in the body section of each logical page. When a line is not numbered, the current line number is not incremented, but the line number separator character is still prepended to the line. The styles are:
number all lines,
number only nonempty lines (default for body),
do not number lines (default for header and footer),
number only lines that contain a match for the basic regular
See Regular Expressions in The GNU Grep Manual.
Set the section delimiter characters to
cd; default is
\:’. If only
c is given, the second remains ‘
(Remember to protect ‘
\’ or other metacharacters from shell
expansion with quotes or extra backslashes.)
Increment line numbers by
number (default 1).
number (default 1) consecutive empty lines to be one
logical line for numbering, and only number the last one. Where fewer
number consecutive empty lines occur, do not number them.
An empty line is one that contains no characters, not even spaces
Select the line numbering format (default is
left justified, no leading zeros;
right justified, no leading zeros;
right justified, leading zeros.
Do not reset the line number at the start of a logical page.
Separate the line number from the text line in the output with
string (default is the TAB character).
Set the initial line number on each logical page to
number (default 1).
number characters for line numbers (default 6).
An exit status of zero indicates success, and a nonzero value indicates failure.