grog
Section: User Commands (1)
Updated: 2 July 2023
Index
Return to Main Contents
Name
grog - lqgroff guessrq-infer the
groff
command a document requires
.nr d-fallback 1
.nr d-fallback 1
Synopsis
[
--run]
[
--ligatures]
[
grof-option~...]
[
--]
[
file~...]
-h
--help
-v
--version
Description
grog
reads its input
and guesses which
options are needed to render it.
If no operands are given,
or if
file
is
[lq]
-[rq],
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
[lq]-[rq]
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,
patter-matching strings that are statistically likely to be
characteristic of
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 no-default output device.
If the input is not encoded in U-ASCII,
ISO 885-1,
or IBM code page 1047,
specification of a
groff
option to run the
preprocessor is advised;
see the
-D,
-k,
and
-K
options of
For UT-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 n-break control characters.
grog
does not parse
roff
input line continuation or control structures
(brace escape sequences and the
[lq]
if[rq],
[lq]
ie[rq],
and
[lq]
el[rq]
requests)
nor
groff's
[lq]
while[rq].
Thus the input
-
.if [rs]
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
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
[lq]
soelim[rq]ed
input causes
grog
to infer additional preprocessor options,
then
-s
is likely necessary.
-
$ printf [dq].TS[rs]nl.[rs]nI[aq]m a table.[rs]n.TE[rs]n[dq] > 3.roff
$ printf [dq].so 3.roff[rs]n[dq] > 2.roff
$ printf [dq].XP[rs]n.so 2.roff[rs]n[dq] > 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
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-1.23.0/meintro.me
at the command line results in
-
groff -me /usr/: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/:share/:doc/:groff-1.23.0/pic.ms
outputs
-
groff -e -p -t -ms /usr/: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
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-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
and heavily revised by
G. Branden Robinson
See also
Index
- Name
-
- Synopsis
-
- Description
-
- Options
-
- Details
-
- Limitations
-
- Exit status
-
- Examples
-
- Authors
-
- See also
-
|
|
- Running on 
-
:
