‘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:
‘\:\:\:’
start of header;‘\:\:’
start of body;‘\:’
start of footer.
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.
man nl (BSD)
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.
POSIX
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.
