grog(1) man page

grog(1) General Commands Manual grog(1)

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 /opt/homebrew/Cellar/groff/1.23.0_1/share/doc/groff-1.23.0/meintro.me
at the command line results in
groff -me /opt/homebrew/Cellar/groff/1.23.0_1/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 /opt/homebrew/Cellar/groff/1.23.0_1/share/doc/groff-1.23.0/pic.ms
outputs
groff -e -p -t -ms /opt/homebrew/Cellar/groff/1.23.0_1/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
/opt/homebrew/Cellar/groff/1.23.0_1/share/doc/groff-1.23.0 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>.