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

Name

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

Synopsis

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

       grog -h
       grog --help

       grog -v
       grog --version

Description

       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.  With the
       option --run, the inferred command is written  to  the  standard  error  stream  and  then
       executed.

Options

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

       --ligatures
              includes the arguments -P-y -PU in the inferred groff command.  These are supported
              only by the pdf output device.

       --run  writes the inferred command to the standard error stream and then executes it.

       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

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

       grog  exits  with  error  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.  (If the --run option is specified,
       groff's exit status is discarded.)  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

       Running
              grog /usr/share/doc/groff-base/meintro.me
       at the command line results in
              groff -me /usr/share/doc/groff-base/meintro.me
       because grog recognizes that the file meintro.me is  written  using  macros  from  the  me
       package.  The command
              grog /usr/share/doc/groff-base/pic.ms
       outputs
              groff -e -p -t -ms /usr/share/doc/groff-base/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/share/doc/groff-base if you'd like to
       try this example yourself.)

Authors

       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⟩.