NAME
groff_trace - groff macro package trace.tmac
SYNOPSIS
[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.
AUTHOR
Copyright (C) 2002, 2006, 2007, 2008 Free Software Foundation, Inc.
This document is distributed under the terms of the FDL (GNU Free
Documentation License) version 1.1 or later. You should have received
a copy of the FDL on your system, it is also available on-line at the
GNU copyleft site
This document is part of groff, the GNU roff distribution. It was
written by Bernd Warken.
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.