Linux Manual Pages

Free Software * Books

Source Code

Free Media

Linux

GROFF_TRACE

NAME
SYNOPSIS
DESCRIPTION
EXAMPLES
PROBLEMS
FILES
ENVIRONMENT
AUTHOR
SEE ALSO

NAME

groff_trace − groff macro package trace.tmac

SYNOPSIS

groff −m trace

[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

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 ("http://www.gnu.org/copyleft/fdl.html") GNU copyleft site.

This document is part of groff, the GNU roff distribution. It was written by Bernd Warken <groff-bernd.warken-72@web.de>.

Opportunity

Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.

Education

Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.