xenial (1) lexgrog.1.gz

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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.