groff_trace(7) — Linux manual page

Name | Synopsis | Description | Example | Problems | Files | Authors | See also | COLOPHON

groff_trace(7)      Miscellaneous Information Manual      groff_trace(7)

Name         top

       groff_trace - GNU roff macros for debugging groff documents

Synopsis         top

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

Description         top

       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.  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 the 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.

Example         top

       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         top

       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         top

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

Authors         top

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

See also         top

       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.

       groff_tmac(5)
              A general description of groff macro packages.

       groff(7)
              A short reference for the groff formatting language.

COLOPHON         top

       This page is part of the groff (GNU troff) project.  Information
       about the project can be found at 
       ⟨http://www.gnu.org/software/groff/⟩.  If you have a bug report
       for this manual page, see ⟨http://www.gnu.org/software/groff/⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://git.savannah.gnu.org/git/groff.git⟩ on 2021-06-20.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2021-06-17.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

groff 1.23.0.rc1.654-4e1db-dirt1y6 June 2021                groff_trace(7)

Pages that refer to this page: groff_tmac(5)