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.

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.

COPYING

       Copyright © 2002-2014 Free Software Foundation, Inc.

       This file is part of groff, the GNU roff type-setting system.

       Permission is granted to copy, distribute and/or modify this document under the terms  of  the  GNU  Free
       Documentation  License,  Version 1.3 or any later version published by the Free Software Foundation; with
       the Invariant Sections being this .ig-section and AUTHOR, with no Front-Cover Texts, and  with  no  Back-
       Cover Texts.

       A  copy  of  the Free Documentation License is included as a file called FDL in the main directory of the
       groff source package.

AUTHORS

       Written by Bernd Warken.

Groff Version 1.22.3                             28 January 2016                                  GROFF_TRACE(7)