.TH GROFF_TRACE 7 "27 January 2021" "groff 1.22.4"
.SH NAME
groff_trace \- groff macro package trace.tmac
.
.\" groff_trace.7
.\" File position: <groff-source>/tmac/groff_trace.man
.
.
.\" Save and disable compatibility mode (for, e.g., Solaris 10/11).
.do nr groff_trace_C \n[.C]
.cp 0
.
.
.\" ====================================================================
.\" Legal Terms
.\" ====================================================================
.\"
.\" Copyright (C) 2002-2018 Free Software Foundation, Inc.
.\"
.\" This file is part of groff, the GNU roff type-setting system.
.\"
.\" Permission is granted to copy, distribute and/or modify this
.\" document under the terms of the GNU Free Documentation License,
.\" Version 1.3 or any later version published by the Free Software
.\" Foundation; with no Invariant Sections, with no Front-Cover Texts,
.\" and with no Back-Cover Texts.
.\"
.\" A copy of the Free Documentation License is included as a file
.\" called FDL in the main directory of the groff source package.
.\"
.\" A copy of the GNU Free Documentation License is also available in this
.\" Debian package as /usr/share/doc/groff/copyright.
.
.
.\" ====================================================================
.SH SYNOPSIS
.\" ====================================================================
.
.SY "groff \-m trace"
.RI [ option
\&.\|.\|.\&]
.RI [ input-file
\&.\|.\|.\&]
.YS
.
.
.\" ====================================================================
.SH DESCRIPTION
.\" ====================================================================
.
The
.I trace
macro package of
.BR 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.
.
.
.P
This tracing process is activated by specifying the groff or troff
command-line option
.BR \-m\ trace .
.
This works also with the
.BR groffer (1)
viewer program.
.
A finer control can be obtained by including the macro file within the
document by the groff macro call
.BR .mso\ trace.tmac .
.
Only macros that are defined after this line are traced.
.
.
.P
If the command-line option
.B \-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.
.
.
.P
If some other macro package should be traced as well it must be
specified after
.B \-m\ trace
on the command line.
.
.
.P
The macro file
.B 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.
.
.
.\" ====================================================================
.SH 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
.IR /dev/null .
.
The resulting diagnostic messages are displayed directly below the
corresponding example.
.
.
.\" ====================================================================
.SS "Command line option"
Example:
.
.RS
.P
.EX
\fIsh#\fP echo \[aq].
> .de test_macro
> ..
> .test_macro
> .test_macro some dummy arguments
> \[aq] | 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"
.EE
.RE
.
.P
The entry and the exit of each macro call is displayed on the terminal
(standard output) \[em] together with the arguments (if any).
.
.
.\" ====================================================================
.SS "Nested macro calls"
Example:
.
.RS
.P
.EX
\fIsh#\fP echo \[aq].
> .de child
> ..
> .de parent
> .child
> ..
> .parent
> \[aq] | groff \-m trace > /dev/null

*** .de child
*** .de parent
*** de trace enter: .parent
 *** de trace enter: .child
 *** trace exit: .child
*** trace exit: .parent
.EE
.RE
.
.P
This shows that macro calls can be nested.
.
This powerful feature can help to tack down quite complex call stacks.
.
.
.\" ====================================================================
.SS "Activating with .mso"
Example:
.
.RS
.P
.EX
\fIsh#\fP echo \[aq].
> .de before
> ..
> .mso trace.tmac
> .de after
> ..
> .before
> .after
> .before
> \[aq] | groff > /dev/null

*** de trace enter: .after
*** trace exit: .after
.EE
.RE
.
.P
Here, the tracing is activated within the document, not by a
command-line option.
.
As tracing was not active when macro
.I before
was defined, no call of this macro is protocolled; on the other hand,
the macro
.I after
is fully protocolled.
.
.
.\" ====================================================================
.SH PROBLEMS
.\" ====================================================================
.
Because
.B trace.tmac
wraps the
.B .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
.
.IP
.EX
\&.foo \e\e\e\en[bar]
.EE
.
.
.P
normally passes \[oq]\e\en[bar]\[cq] to macro \[oq].foo\[cq], but with
the redefined
.B .de
request it passes \[oq]\en[bar]\[cq] instead.
.
.
.P
The solution to this problem is to use groff's
.B \eE
escape which is an escape character not interpreted in copy mode, for
example
.
.IP
.EX
\&.foo \eEn[bar]
.EE
.
.
.\" ====================================================================
.SH FILES
.\" ====================================================================
.
The
.I trace
macros are kept in the file
.B trace.tmac
located in the
.IR "tmac directory" ;
see
.BR groff_tmac (5)
for details.
.
.
.\" ====================================================================
.SH ENVIRONMENT
.\" ====================================================================
.
.TP
.I GROFF_TMAC_PATH
A colon-separated list of additional tmac directories in which to
search for macro files; see
.BR groff_tmac (5)
for details.
.
.
.\" ====================================================================
.SH AUTHORS
.\" ====================================================================
.
The
.I trace
macro packages was written by James Clark.
.
This document was written by
.MT groff\-bernd.warken\-72@\:web.de
Bernd Warken
.ME .
.
.
.\" ====================================================================
.SH "SEE ALSO"
.\" ====================================================================
.
.IR "Groff: The GNU Implementation of troff" ,
by Trent A.\& Fisher and Werner Lemberg,
is the primary
.I groff
manual.
.
You can browse it interactively with \[lq]info groff\[rq].
.
.
.TP
.BR groff (1)
An overview of the groff system.
.
.TP
.BR troff (1)
For details on option
.BR \-m .
.
.TP
.BR groffer (1)
A viewer program for all kinds of roff documents.
.
.TP
.BR groff_tmac (5)
A general description of groff macro packages.
.
.TP
.BR groff (7)
A short reference for the groff formatting language.
.
.\" Restore compatibility mode (for, e.g., Solaris 10/11).
.cp \n[groff_trace_C]
.
.
.\" Local Variables:
.\" mode: nroff
.\" End:
.\" vim: set filetype=groff: