man > GROFF_TRACE(7)

GROFF_TRACE(7)                    Miscellaneous Information Manual                    GROFF_TRACE(7)



NAME
       groff_trace - groff macro package trace.tmac

SYNOPSIS
       groff -m trace [option ...] [input-file ...]

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 ob‐
       tained  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  the command-line option -r trace-full=1 is given (or if this register is set in the docu‐
       ment), 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 for‐
       matted 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 in‐
       terpreted 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.

AUTHORS
       The  trace  macro  packages  was  written by James Clark.  This document was written by Bernd
       Warken ⟨groff-bernd.warken-72 AT web.de⟩.

SEE ALSO
       Groff: The GNU Implementation of troff, by Trent A. Fisher and Werner Lemberg, is the primary
       groff manual.  You can browse it interactively with “info groff”.

       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.



groff 1.22.4                                23 March 2022                             GROFF_TRACE(7)