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 ]8;;man:groff(1)\groff(1)]8;;\ 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 in-
ferred command is written to the standard error stream and then exe-
cuted.
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 statis-
tically likely to be characteristic of ]8;;man:roff(7)\roff(7)]8;;\ 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 in-
ferred 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 ]8;;man:preconv(1)\preconv(1)]8;;\ preprocessor is advised; see the -D, -k,
and -K options of ]8;;man:groff(1)\groff(1)]8;;\. 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 con-
tinuation 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 con-
structions 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 imme-
diately follow the default control character at the beginning of a
line.
Detection of the -s option (the ]8;;man:soelim(1)\soelim(1)]8;;\ 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 condi-
tions 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 pre-
processor 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 ]8;;man:tbl(1)\tbl(1)]8;;\ macros, so we would add -s as well as the detected -t op-
tion 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 rec-
ognizes 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 ]8;;man:gremlin(1)\gremlin(1)]8;;\ 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 cur-
rent implementation in Perl was written by ]8;;mailto:groff-bernd.warken-72@web.de\Bernd Warken]8;;\ and heavily re-
vised by ]8;;mailto:g.branden.robinson@gmail.com\G. Branden Robinson]8;;\.
See also
]8;;man:groff(1)\groff(1)]8;;\
groff 1.23.0 31 March 2024 grog(1)
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