lexgrog(1) — Linux manual page


LEXGROG(1)                   Manual pager utils                   LEXGROG(1)

NAME         top

       lexgrog - parse header information in man pages

SYNOPSIS         top

       lexgrog [-m|-c] [-dfw?V] [-E encoding] file ...

DESCRIPTION         top

       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         top

       -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.

              Print a short usage message and exit.

       -V, --version
              Display version information.

EXIT STATUS         top

       0      Successful program execution.

       1      Usage error.

       2      lexgrog failed to parse one or more of its input files.

EXAMPLES         top

         $ 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

WHATIS PARSING         top

       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

       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

              .SH NAME
              foo, bar \- programs to do something
              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         top

       apropos(1), man(1), whatis(1), mandb(8)

NOTES         top

       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         top

       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.

BUGS         top


COLOPHON         top

       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
       ⟨http://git.savannah.gnu.org/r/man-db.git⟩ on 2020-07-14.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-07-04.)  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

2.8.4                            2018-07-27                       LEXGROG(1)

Pages that refer to this page: man(7)mandb(8)