groff_trace(7) — Linux manual page

Name | Synopsis | Description | Example | Problems | Files | Environment | Authors | See Also | COLOPHON

groff_trace(7)        Miscellaneous Information Manual        groff_trace(7)

Name         top

       groff_trace - groff macro package trace.tmac

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

       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

              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 termi‐
       nal (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.

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.

Environment         top

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

Authors         top

       The trace macro packages was written by James Clark.  This document
       was written by Bernd Warken ⟨⟩.

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”.

              An overview of the groff system.

              For details on option -m.

              A general description of groff macro packages.

              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 
       ⟨⟩.  If you have a bug report for
       this manual page, see ⟨⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨⟩ on 2020-07-14.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-07-12.)  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

groff            16 May 2020                  groff_trace(7)

Pages that refer to this page: groff(1)groff_tmac(5)