GROFF_TRACE(7)	       Miscellaneous Information Manual		GROFF_TRACE(7)

NAME
       groff_trace - groff macro package trace.tmac

SYNOPSIS
       groff -m	trace [option ...] [input-file ...]

DESCRIPTION
       The  trace  macro package of groff(1) can be a valuable tool for	debug-
       ging documents written in the roff formatting language.	A  call	 stack
       trace  is  protocolled on standard error, this is, a diagnostic message
       is emitted on entering and exiting of a macro call.  This greatly eases
       to track	down an	error in some macro.

       This tracing process is activated by specifying the groff or troff com-
       mand-line option	-m trace.  This	works also with	the groffer(1)	viewer
       program.	  A  finer control can be obtained by including	the macro file
       within the document by the  groff  macro	 call  .mso trace.tmac.	  Only
       macros that are defined after this line are traced.

       If  the command-line option -r trace-full=1 is given (or	if this	regis-
       ter is set in the document), number and string register assignments to-
       gether with some	other requests are traced also.

       If  some	other macro package should be traced as	well it	must be	speci-
       fied after -m trace on the command line.

       The macro file trace.tmac is unusual because it does  not  contain  any
       macros  to be called by a user.	Instead, the existing macro definition
       and appending facilities	are modified such that they display diagnostic
       messages.

EXAMPLES
       In  the following examples, a roff fragment is fed into groff via stan-
       dard input.  As we are  only  interested	 in  the  diagnostic  messages
       (standard error)	on the terminal, the normal formatted output (standard
       output) is redirected to	the nirvana device /dev/null.	The  resulting
       diagnostic  messages are	displayed directly below the corresponding ex-
       ample.

   Command line	option
       Example:

	      sh# echo '.
	      >	.de test_macro
	      >	..
	      >	.test_macro
	      >	.test_macro some dummy arguments
	      >	' | groff -m trace > /dev/null

	      *** .de test_macro
	      *** de trace enter: .test_macro
	      *** trace	exit: .test_macro
	      *** de trace enter: .test_macro "some" "dummy" "arguments"
	      *** trace	exit: .test_macro "some" "dummy" "arguments"

       The entry and the exit of each macro call is displayed on the  terminal
       (standard output) -- together with the arguments	(if any).

   Nested macro	calls
       Example:

	      sh# echo '.
	      >	.de child
	      >	..
	      >	.de parent
	      >	.child
	      >	..
	      >	.parent
	      >	' | groff -m trace > /dev/null

	      *** .de child
	      *** .de parent
	      *** de trace enter: .parent
	       *** de trace enter: .child
	       *** trace exit: .child
	      *** trace	exit: .parent

       This  shows  that macro calls can be nested.  This powerful feature can
       help to tack down quite complex call stacks.

   Activating with .mso
       Example:

	      sh# echo '.
	      >	.de before
	      >	..
	      >	.mso trace.tmac
	      >	.de after
	      >	..
	      >	.before
	      >	.after
	      >	.before
	      >	' | groff > /dev/null

	      *** de trace enter: .after
	      *** trace	exit: .after

       Here, the tracing is activated within the document, not by  a  command-
       line  option.  As tracing was not active	when macro before was defined,
       no call of this macro is	protocolled; on	the other hand,	the macro  af-
       ter is fully protocolled.

PROBLEMS
       Because trace.tmac wraps	the .de	request	(and its cousins), macro argu-
       ments are expanded one level more.  This	causes problems	if an argument
       contains	four backslashes or more to prevent too	early expansion	of the
       backslash.  For example,	this macro call

	      .foo \\\\n[bar]

       normally	passes `\\n[bar]' to macro `.foo', but with the	redefined  .de
       request it passes `\n[bar]' instead.

       The  solution  to  this problem is to use groff's \E escape which is an
       escape character	not interpreted	in copy	mode, for example

	      .foo \En[bar]

FILES
       The trace macros	are kept in the	file trace.tmac	located	 in  the  tmac
       directory; see groff_tmac(5) for	details.

ENVIRONMENT
       GROFF_TMAC_PATH
	      A	 colon-separated  list of additional tmac directories in which
	      to search	for macro files; see groff_tmac(5) for details.

AUTHORS
       The trace macro packages	was written by James Clark.  This document was
       written by Bernd	Warken <groff-bernd.warken-72@web.de>.

SEE ALSO
       Groff:  The  GNU	Implementation of troff, by Trent A. Fisher and	Werner
       Lemberg,	is the primary groff manual.  You can browse it	 interactively
       with "info groff".

       groff(1)
	      An overview of the groff system.

       troff(1)
	      For details on option -m.

       groffer(1)
	      A	viewer program for all kinds of	roff documents.

       groff_tmac(5)
	      A	general	description of groff macro packages.

       groff(7)
	      A	short reference	for the	groff formatting language.

groff 1.22.4		       29 November 2018			GROFF_TRACE(7)