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       groff_trace - groff macro package trace.tmac


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       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


       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

   Command line option

              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"

       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

              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

              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.


       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]


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


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


       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

       This  document  is  part  of  groff, the GNU roff distribution.  It was
       written by Bernd Warken.


              An overview of the groff system.

              For details on option -m.

              A viewer program for all kinds of roff documents.

              A general description of groff macro packages.

              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.