GROFF_TRACE(7)                                                                                                    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 lan-
       guage.  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  exist-
       ing 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 diag-
       nostic messages (standard error) on the terminal, the normal formatted output (standard output) is redirected to the nir-
       vana 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 1.20.1                                     9 January 2009                                           GROFF_TRACE(7)