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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | EXAMPLES | WHATIS PARSING | SEE ALSO | NOTES | AUTHOR | BUGS | COLOPHON |
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LEXGROG(1) Manual pager utils LEXGROG(1)
lexgrog - parse header information in man pages
lexgrog [-m|-c] [-dfw?V] [-E encoding] file ...
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.
-d, --debug
Print debugging information.
-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.
-?, --help
Print a help message and exit.
--usage
Print a short usage message and exit.
-V, --version
Display version information.
0 Successful program execution.
1 Usage error.
2 lexgrog failed to parse one or more of its input files.
$ lexgrog man.1
man.1: "man - an interface to the system reference manuals"
$ lexgrog -fw man.1
man.1 (t): "man - an interface to the system reference manuals"
$ lexgrog -c whatis.cat1
whatis.cat1: "whatis - display manual page descriptions"
$ lexgrog broken.1
broken.1: parse failed
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.
apropos(1), man(1), whatis(1), mandb(8)
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.
The code used by lexgrog to scan man pages was written by:
Wilf. (G.Wilford@ee.surrey.ac.uk).
Fabrizio Polacco (fpolacco@debian.org).
Colin Watson (cjwatson@debian.org).
Colin Watson wrote the current incarnation of the command-line
front-end, as well as this man page.
https://gitlab.com/man-db/man-db/-/issues
https://savannah.nongnu.org/bugs/?group=man-db
This page is part of the man-db (manual pager suite) project.
Information about the project can be found at
⟨http://www.nongnu.org/man-db/⟩. If you have a bug report for this
manual page, send it to man-db-devel@nongnu.org. This page was
obtained from the project's upstream Git repository
⟨https://gitlab.com/cjwatson/man-db⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-05-19.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
2.13.1 2025-05-02 LEXGROG(1)
Pages that refer to this page: mansect(1), mandb(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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