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  preprocess-
       ing  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.

              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 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

       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 neverthe-
       less 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 be-
       haviour on certain ill-formed NAME sections.  The text  on  the  right-
       hand side is free-form, and may be spread over multiple lines.  If sev-
       eral 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 informa-
       tion 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.

2.8.3                             2018-04-05                        LEXGROG(1)
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