GROFF_TRACE(7)             OpenBSD Reference 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
       debugging 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
       command 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
       specified 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
       standard 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
       arguments 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
       Documentation 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.

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 1.21             31 December 2010                 GROFF_TRACE(7)
