lexgrog
parse header information in man pages
see also :
apropos - man - whatis - mandb
Synopsis
lexgrog
[-m|-c] [-fhwV]
[-E encoding] file ...
add an example, a script, a trick and tips
examples
$ lexgrog man.1
man.1: "man - an interface to the on-line reference manuals"
$ lexgrog -fw man.1
man.1 (t): "man - an interface to the on-line reference
manuals"
$ lexgrog -c whatis.cat1
whatis.cat1: "whatis - display manual page descriptions"
$ lexgrog broken.1
broken.1: parse failed
description
lexgrog
is an implementation of the traditional “groff
guess” utility in lex. It reads the list of
files on its command line as either man page source files or
preformatted “cat” pages, and displays their
name and description as used by apropos and
whatis, the list of preprocessing filters required by
the man page before it is passed to nroff or
troff, or both.
If its input is
badly formatted, lexgrog will print “parse
failed”; this may be useful for external programs that
need to check man pages for correctness. If one of
lexgrog’s input files is “-”,
it will read from standard input; if any input file is
compressed, a decompressed version will be read
automatically.
options
-m,
--man
Parse input as man page source
files. This is the default if neither
--man nor --cat is
given.
-c,
--cat
Parse input as preformatted man
pages (“cat pages”). --man
and --cat may not be given
simultaneously.
-w,
--whatis
Display the name and
description from the man page’s header, as used by
apropos and whatis. This is the default if
neither --whatis nor
--filters is given.
-f,
--filters
Display the list of filters
needed to preprocess the man page before formatting with
nroff or troff.
-E
encoding, --encoding
encoding
Override the guessed character
set for the page to encoding.
-h,
--help
Print a help message and
exit.
-V,
--version
Display version
information.
exit status
0
Successful program execution.
1
Usage error.
2
lexgrog failed to parse one or more of its input files.
notes
lexgrog attempts to parse files containing .so requests,
but will only be able to do so correctly if the files are
properly installed in a manual page hierarchy.
whatis parsing
mandb (which uses the same code as lexgrog) parses
the NAME section at the top of each manual page looking
for names and descriptions of the features documented in each.
While the parser is quite tolerant, as it has to cope with a
number of different forms that have historically been used, it
may sometimes fail to extract the required information.
When using the traditional man macro set, a correct
NAME section looks something like this:
.SH NAME
foo \- program to do something
Some manual pagers require the ’\-’ to be exactly as shown;
mandb is more tolerant, but for compatibility with other
systems it is nevertheless a good idea to retain the backslash.
On the left-hand side, there may be several names, separated by
commas. Names containing whitespace will be ignored to avoid
pathological behaviour on certain ill-formed NAME
sections. The text on the right-hand side is free-form, and may
be spread over multiple lines. If several features with different
descriptions are being documented in the same manual page, the
following form is therefore used:
.SH NAME
foo, bar \- programs to do something
.br
baz \- program to do nothing
(A macro which starts a new paragraph, like .PP, may be
used instead of the break macro .br.)
When using the BSD-derived mdoc macro set, a correct
NAME section looks something like this:
.Sh NAME
.Nm foo
.Nd program to do something
There are several common reasons why whatis parsing fails.
Sometimes authors of manual pages replace ’.SH NAME’ with ’.SH
MYPROGRAM’, and then mandb cannot find the section from
which to extract the information it needs. Sometimes authors
include a NAME section, but place free-form text there rather
than ’name \- description’. However, any syntax resembling the
above should be accepted.
see also
apropos ,
man , whatis , mandb
author
The code used
by lexgrog to scan man pages was written by:
Wilf.
(G.Wilford[:at:]ee.surrey.ac[:dot:]uk).
Fabrizio Polacco (fpolacco[:at:]debian[:dot:]org).
Colin Watson (cjwatson[:at:]debian[:dot:]org).
Colin Watson
wrote the current incarnation of the command-line front-end,
as well as this man page.