.TH grog 1 "4 October 2023" "groff 1.23.0"
.SH Name
grog \- \(lqgroff guess\(rq\(eminfer the
.I groff
command a document requires
.
.
.\" ====================================================================
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.\" ====================================================================
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.\"
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.\" ====================================================================
.SH Synopsis
.\" ====================================================================
.
.SY grog
.RB [ \-\-run ]
.RB [ \-\-ligatures ]
.RI [ groff-option\~ .\|.\|.\&]
.RB [ \-\- ]
.RI [ file\~ .\|.\|.]
.YS
.
.
.SY grog
.B \-h
.
.SY grog
.B \-\-help
.YS
.
.
.SY grog
.B \-v
.
.SY grog
.B \-\-version
.YS
.
.
.\" ====================================================================
.SH Description
.\" ====================================================================
.
.I grog
reads its input
and guesses which
.MR groff 1
options are needed to render it.
.
If no operands are given,
or if
.I file
is
.RB \[lq] \- \[rq],
.I grog
reads the standard input stream.
.
The corresponding
.I groff
command is normally written to the standard output stream.
.
With the option
.BR \-\-run ,
the inferred command is written to the standard error stream and then
executed.
.
.
.\" ====================================================================
.SH Options
.\" ====================================================================
.
.B \-h
and
.B \-\-help
display a usage message,
whereas
.B \-v
and
.B \-\-version
display version information;
all exit afterward.
.
.
.TP
.B \-\-ligatures
includes the arguments
.B \-P\-y \-PU
in the inferred
.I groff
command.
.
These are supported only by the
.B pdf
output device.
.
.
.TP
.B \-\-run
writes the inferred command to the standard error stream and then
executes it.
.
.
.P
All other specified short options
(that is,
arguments beginning with a minus sign
.RB \[lq] \- \[rq]
followed by a letter)
are interpreted as
.I groff
options or option clusters with or without an option argument.
.
Such options are included in the constructed
.I groff
command line.
.
.
.\" ====================================================================
.SH Details
.\" ====================================================================
.
.I grog
reads each
.I file
operand,
pattern-matching strings that are statistically likely to be
characteristic of
.MR roff 7
documents.
.
It tries to guess which of the following
.I groff
options are required to correctly render the input:
.BR \-e ,
.BR \-g ,
.BR \-G ,
.BR \-j ,
.\" gideal is not implemented yet.
.\" .BR \-J ,
.BR \-p ,
.BR \-R ,
.\".BR \-s ,
.B \-t
(preprocessors);
and
.BR \-man ,
.BR \-mdoc ,
.BR \-mdoc\-old ,
.BR \-me ,
.BR \-mm ,
.BR \-mom ,
and
.B \-ms
(macro packages).
.
The inferred
.I groff
command including these options and any
.I file
parameters is written to the standard output stream.
.
.
.P
It is possible to specify arbitrary
.I groff
options on the command line.
.
These are included in the inferred command without change.
.
Choices of
.I groff
options include
.B \-C
to enable AT&T
.I troff
compatibility mode and
.B \-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
.I groff
option to run the
.MR preconv 1
preprocessor is advised;
see the
.BR \-D ,
.BR \-k ,
and
.B \-K
options of
.MR groff 1 .
.
For UTF-8 input,
.B \-k
is a good choice.
.
.
.P
.I groff
may issue diagnostic messages when an inappropriate
.B \-m
option,
or multiple conflicting ones,
are specified.
.
Consequently,
it is best to specify no
.B \-m
options to
.I grog
unless it cannot correctly infer all of the
.B \-m
arguments a document requires.
.
A
.I roff
document can also be written without recourse to any macro package.
.
In such cases,
.I grog
will infer a
.I groff
command without an
.B \-m
option.
.
.
.\" ====================================================================
.SS Limitations
.\" ====================================================================
.
.I grog
presumes that the input does not change the escape,
control,
or no-break control characters.
.
.I grog
does not parse
.I roff
input line continuation or control structures
(brace escape sequences and the
.RB \[lq] if \[rq],
.RB \[lq] ie \[rq],
and
.RB \[lq] el \[rq]
requests)
nor
.IR groff 's
.RB \[lq] while \[rq].
.
Thus the input
.
.RS
.EX
\&.if \[rs]
t .NH 1
\&.if n .SH
Introduction
.EE
.RE
.
will conceal the use of the
.I ms
macros
.B NH
and
.B SH
from
.IR grog .
.
Such constructions are regarded by
.IR 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.
.
.IR pic ,
for example,
requires
.BR PS ,
.BR PE ,
and
.B PF
calls to immediately follow the default control character at the
beginning of a line.
.
.
.P
Detection of the
.B \-s
option
(the
.MR \%soelim 1
preprocessor)
is tricky;
to correctly infer its necessity would require
.I grog
to recursively open all files given as arguments to the
.B .so
request under the same conditions that
.I \%soelim
itself does so;
see its man page.
.
Recall that
.I \%soelim
is necessary only if sourced files need to be preprocessed.
.
Therefore,
as a workaround,
you may want to run the input through
.I \%soelim
manually,
piping it to
.IR grog ,
and compare the output to running
.I grog
on the input directly.
.
If the
.RI \[lq] \%soelim \[rq]ed
input causes
.I grog
to infer additional preprocessor options,
then
.B \-s
is likely necessary.
.
.
.RS
.P
.EX
$ \c
.B printf \[dq].TS\[rs]nl.\[rs]nI\[aq]m a table.\[rs]n.TE\[rs]n\[dq] > \
3.roff
$ \c
.B printf \[dq].so 3.roff\[rs]n\[dq] > 2.roff
$ \c
.B printf \[dq].XP\[rs]n.so 2.roff\[rs]n\[dq] > 1.roff
$ \c
.B grog 1.roff
groff \-ms 1.roff
$ \c
.B \%soelim 1.roff | grog
groff \-t \-ms \-
.EE
.RE
.
.
.P
In the foregoing example,
we see that this procedure enabled
.I grog
to detect
.MR \%tbl 1
macros,
so we would add
.B \-s
as well as the detected
.B \-t
option to a revised
.I grog
or
.I groff
command.
.
.
.RS
.P
.EX
$ \c
.B grog \-st 1.roff
groff \-st \-ms 1.roff
.EE
.RE
.
.
.\" ====================================================================
.SH "Exit status"
.\" ====================================================================
.
.I grog
exits with error status
.B 1
if a macro package appears to be in use by the input document,
but
.I grog
was unable to infer which one,
or
.B 2
if there were problems handling an option or operand.
.
It otherwise exits with status
.BR 0 .
.
(If the
.B \-\-run
option is specified,
.IR groff 's
exit status is discarded.)
.
Inferring no preprocessors or macro packages is not an error condition;
a valid
.I 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.
.
.
.\" ====================================================================
.SH Examples
.\" ====================================================================
.
Running
.
.RS
.EX
.B grog /usr/\:\%share/\:\%doc/\:\%packages/\:\%groff/meintro.me
.EE
.RE
at the command line results in
.RS
.EX
groff \-me /usr/\:\%share/\:\%doc/\:\%packages/\:\%groff/meintro.me
.EE
.RE
.
because
.I grog
recognizes that the file
.I meintro.me
is written using macros from the
.I me
package.
.
The command
.
.RS
.EX
.B grog /usr/\:\%share/\:\%doc/\:\%packages/\:\%groff/pic.ms
.EE
.RE
.
outputs
.
.RS
.EX
groff \-e \-p \-t \-ms /usr/\:\%share/\:\%doc/\:\%packages/\:\%groff/pic.ms
.EE
.RE
.
on the other hand.
.
Besides discerning the
.I ms
macro package,
.I grog
recognizes that the file
.I pic.ms
additionally needs the combination of
.B \-t
for
.IR tbl ,
.B \-e
for
.IR eqn ,
and
.B \-p
for
.IR pic .
.
.
.\" XXX: grog no longer (June 2021) attempts to detect this scenario.
.\" It's also not a practical one; full-service macro packages don't
.\" generally support being "unloaded" for subsequent processing of
.\" another document using a different one.  We do achieve it, with
.\" care, in groff with man(7) and mdoc(7) (see andoc.tmac).
.\" .P
.\" If both of the former example files are combined in the command
.\" .
.\" .RS
.\" .EX
.\" .B grog meintro.me pic.ms
.\" .EE
.\" .RE
.\" .
.\" a diagnostic message is sent to the standard error stream because
.\" some macro packages cannot be combined.
.\" .
.\" Nevertheless the corresponding output with the wrong options is
.\" written to standard output:
.\" .
.\" .RS
.\" .EX
.\" groff \-t \-e \-p \-ms meintro.me pic.ms
.\" .EE
.\" .RE
.\" .
.\" and
.\" .I grog
.\" terminates with an error exit status.
.
.
.P
Consider a file
.IR \%doc/\:\%grnexampl.me ,
which uses the
.I \%grn
preprocessor to include a
.MR gremlin 1
picture file in an
.I me \" generic
document.
.
Let's say we want to suppress color output,
produce a DVI file,
and get backtraces for any errors that
.I \%troff
encounters.
.
The command
.
.RS
.EX
.B grog \-bc \-Idoc \-Tdvi doc/grnexmpl.me
.EE
.RE
.
is processed by
.I grog
into
.
.RS
.EX
groff \-bc \-Idoc \-Tdvi \-e \-g \-me doc/grnexmpl.me
.EE
.RE
.
where we can see that
.I grog
has inferred the
.I me \" generic
macro package along with the
.I eqn \" generic
and
.I grn \" generic
preprocessors.
.
(The input file is located in
.I /usr/\:\%share/\:\%doc/\:\%packages/\:\%groff
if you'd like to try this example yourself.)
.
.
.\" ====================================================================
.SH Authors
.\" ====================================================================
.
.I grog
was originally written in Bourne shell by James Clark.
.
The current implementation in Perl was written by
.MT groff\-bernd\:.warken\-72@\:web\:.de
Bernd Warken
.ME
and heavily revised by
.MT g.branden\:.robinson@\:gmail\:.com
G.\& Branden Robinson
.ME .
.
.
.\" ====================================================================
.SH "See also"
.\" ====================================================================
.
.MR groff 1
.
.
.\" Restore compatibility mode (for, e.g., Solaris 10/11).
.cp \n[*groff_grog_1_man_C]
.do rr *groff_grog_1_man_C
.
.
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