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groff_trace(7) Miscellaneous Information Manual groff_trace(7)
groff_trace - GNU roff macros for debugging groff documents
groff -m trace [option ...] [file ...]
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.
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.
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.
The trace macro packages was written by James Clark. This
document was written by Bernd Warken ⟨groff-bernd.warken-72@web
.de⟩.
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.
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 2021-08-27. (At
that time, the date of the most recent commit that was found in
the repository was 2021-08-23.) 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-dir1t9yAugust 2021 groff_trace(7)
Pages that refer to this page: groff_tmac(5)
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