grog(1) — Linux manual page

Name | Synopsis | Description | Options | Details | Exit status | Examples | Authors | See also | COLOPHON

grog(1)                  General Commands Manual                 grog(1)

Name         top

       grog - “groff guess”—infer the groff command a document requires

Synopsis         top

       grog [groff-option ...] [--] [file ...]

       grog -h
       grog --help

       grog -v
       grog --version

Description         top

       grog reads its input and guesses which groff(1) options are
       needed to render it.  If no operands are given, or if file is
       “-”, grog reads the standard input stream.  The corresponding
       groff command is normally written to the standard output stream.

Options         top

       -h and --help display a usage message, whereas -v and --version
       display version information; all exit afterward.

       All other specified short options (that is, arguments beginning
       with a minus sign “-” followed by a letter) are interpreted as
       groff options or option clusters with or without an option
       argument.  Such options are included in the constructed groff
       command line.

Details         top

       grog reads each file operand, pattern-matching strings that are
       statistically likely to be characteristic of roff(7) documents.
       It tries to guess which of the following groff options are
       required to correctly render the input: -e, -g, -G, -j, -p, -R,
       -t (preprocessors); and -man, -mdoc, -mdoc-old, -me, -mm, -mom,
       and -ms (macro packages).  The inferred groff command including
       these options and any file parameters is written to the standard
       output stream.

       It is possible to specify arbitrary groff options on the command
       line.  These are included in the inferred command without change.
       Choices of groff options include -C to enable AT&T troff
       compatibility mode and -T to select a non-default output device.
       If the input is not encoded in US-ASCII, ISO 8859-1, or IBM code
       page 1047, specification of a groff option to run the preconv(1)
       preprocessor is advised; see the -D, -k, and -K options of
       groff(1).  For UTF-8 input, -k is a good choice.

       groff may issue diagnostic messages when an inappropriate -m
       option, or multiple conflicting ones, are specified.
       Consequently, it is best to specify no -m options to grog unless
       it cannot correctly infer all of the -m arguments a document
       requires.  A roff document can also be written without recourse
       to any macro package.  In such cases, grog will infer a groff
       command without an -m option.

   Limitations
       grog presumes that the input does not change the escape, control,
       or no-break control characters.  grog does not parse roff input
       line continuation or control structures (brace escape sequences
       and the “if”, “ie”, and “el” requests) nor groff's “while”.  Thus
       the input
              .if \
              t .NH 1
              .if n .SH
              Introduction
       will conceal the use of the ms macros NH and SH from grog.  Such
       constructions are regarded by grog's implementors as
       insufficiently common to cause many inference problems.
       Preprocessors can be even stricter when matching macro calls that
       bracket the regions of an input file they replace.  pic, for
       example, requires PS, PE, and PF calls to immediately follow the
       default control character at the beginning of a line.

       Detection of the -s option (the soelim(1) preprocessor) is
       tricky; to correctly infer its necessity would require grog to
       recursively open all files given as arguments to the .so request
       under the same conditions that soelim itself does so; see its man
       page.  Recall that soelim is necessary only if sourced files need
       to be preprocessed.  Therefore, as a workaround, you may want to
       run the input through soelim manually, piping it to grog, and
       compare the output to running grog on the input directly.  If the
       “soelim”ed input causes grog to infer additional preprocessor
       options, then -s is likely necessary.

              $ printf ".TS\nl.\nI'm a table.\n.TE\n" > 3.roff
              $ printf ".so 3.roff\n" > 2.roff
              $ printf ".XP\n.so 2.roff\n" > 1.roff
              $ grog 1.roff
              groff -ms 1.roff
              $ soelim 1.roff | grog
              groff -t -ms -

       In the foregoing example, we see that this procedure enabled grog
       to detect tbl(1) macros, so we would add -s as well as the
       detected -t option to a revised grog or groff command.

              $ grog -st 1.roff
              groff -st -ms 1.roff

Exit status         top

       grog exits with status 1 if a macro package appears to be in use
       by the input document, but grog was unable to infer which one, or
       2 if there were problems handling an option or operand.  It
       otherwise exits with status 0.  Inferring no preprocessors or
       macro packages is not an error condition; a valid roff document
       need not use either.  Even plain text is valid input, if one is
       mindful of the syntax of the control and escape characters.

Examples         top

       Running
              grog /usr/local/share/doc/groff-1.23.0/meintro.me
       at the command line results in
              groff -me /usr/local/share/doc/groff-1.23.0/meintro.me
       because grog recognizes that the file meintro.me is written using
       macros from the me package.  The command
              grog /usr/local/share/doc/groff-1.23.0/pic.ms
       outputs
              groff -e -p -t -ms /usr/local/share/doc/groff-1.23.0/pic.ms
       on the other hand.  Besides discerning the ms macro package, grog
       recognizes that the file pic.ms additionally needs the
       combination of -t for tbl, -e for eqn, and -p for pic.

       Consider a file doc/grnexampl.me, which uses the grn preprocessor
       to include a gremlin(1) picture file in an me document.  Let's
       say we want to suppress color output, produce a DVI file, and get
       backtraces for any errors that troff encounters.  The command
              grog -bc -Idoc -Tdvi doc/grnexmpl.me
       is processed by grog into
              groff -bc -Idoc -Tdvi -e -g -me doc/grnexmpl.me
       where we can see that grog has inferred the me macro package
       along with the eqn and grn preprocessors.  (The input file is
       located in /usr/local/share/doc/groff-1.23.0 if you'd like to try
       this example yourself.)

Authors         top

       grog was originally written in Bourne shell by James Clark.  The
       current implementation in Perl was written by Bernd Warken
       ⟨groff-bernd.warken-72@web.de⟩ and heavily revised by G. Branden
       Robinson ⟨g.branden.robinson@gmail.com⟩.

See also         top

       groff(1)

COLOPHON         top

       This page is part of the groff (GNU troff) project.  Information
       about the project can be found at 
       ⟨http://www.gnu.org/software/groff/⟩.  If you have a bug report
       for this manual page, see ⟨http://www.gnu.org/software/groff/⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://git.savannah.gnu.org/git/groff.git⟩ on 2023-12-22.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2023-12-08.)  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

groff 1.23.0.453-330f9-d... 22 December 2023                     grog(1)