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NAME
lexgrog - parse header information in man pages
SYNOPSIS
lexgrog [-m|-c] [-dfw?V] [-E encoding] file ...
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
-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.
EXIT STATUS
0 Successful program execution.
1 Usage error.
2 lexgrog failed to parse one or more of its input files.
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
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(1), man(1), whatis(1), mandb(8)
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.
AUTHOR
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.