GROFF_TRACE(7)	       Miscellaneous Information Manual		GROFF_TRACE(7)



NAME
       groff_trace - groff macro package trace.tmac

SYNOPSIS
       groff -m trace [options ...] [files ...]

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 command line option -r trace-full=1 is given (or if this register is
       set in the document), number and string register	 assignments  together
       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
       example.

   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
       after 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.

AUTHOR
       Copyright (C) 2002, 2006, 2007, 2008 Free Software Foundation, Inc.

       This document is distributed under the terms of the FDL (GNU Free Docu-
       mentation  License)  version  1.1 or later.  You should have received a
       copy of the FDL on your system, it is also available on-line at the GNU
       copyleft site <http://www.gnu.org/copyleft/fdl.html>.

       This  document  is  part	 of  groff, the GNU roff distribution.	It was
       written by Bernd Warken <groff-bernd.warken-72@web.de>.

SEE ALSO
       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.

       A complete reference for all parts of the groff system is found in  the
       groff info(1) file.



Groff Version 1.22.2		7 February 2013			GROFF_TRACE(7)