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

       -?, --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 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
              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

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
       ⟨https://gitlab.com/cjwatson/man-db⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-18.)  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

2.12.0                         2023-09-23                     LEXGROG(1)

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