+</PRE><H3><a name="h3-Command-line-Utilities">Command-line Utilities</a></H3><PRE>
+ The command-line utilities such as <B><A HREF="tic.1M.html">tic(1)</A></B> provide a verbose option
+ which extends the set of messages written using the <B>curses_trace</B> func-
+ tion. Both of these (<B>-v</B> and <B>curses_trace</B>) use the same variable
+ (<B>_nc_tracing</B>), which determines the messages which are written.
+
+ Because the command-line utilities may call initialization functions
+ such as <B>setupterm</B>, <B>tgetent</B> or <B>use_extended_names</B>, some of their debug-
+ ging output may be directed to the <I>trace</I> file if the <B>NCURSES_TRACE</B> en-
+ vironment variable is set:
+
+ <B>o</B> messages produced in the utility are written to the standard error.
+
+ <B>o</B> messages produced by the underlying library are written to <I>trace</I>.
+
+ If ncurses is built without tracing, none of the latter are produced,
+ and fewer diagnostics are provided by the command-line utilities.
+
+
+</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
+ Routines which return a value are designed to be used as parameters to
+ the <B>_tracef</B> routine.
+
+
+</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
+ These functions are not part of the XSI interface. Some other curses
+ implementations are known to have similar features, but they are not
+ compatible with ncurses:
+
+ <B>o</B> SVr4 provided <B>traceon</B> and <B>traceoff</B>, to control whether debugging
+ information was written to the "trace" file. While the functions
+ were always available, this feature was only enabled if <B>DEBUG</B> was
+ defined when building the library.
+
+ The SVr4 tracing feature is undocumented.
+
+ <B>o</B> PDCurses provides <B>traceon</B> and <B>traceoff</B>, which (like SVr4) are al-
+ ways available, and enable tracing to the "trace" file only when a
+ debug-library is built.
+
+ PDCurses has a short description of these functions, with a note
+ that they are not present in X/Open Curses, ncurses or NetBSD. It
+ does not mention SVr4, but the functions' inclusion in a header
+ file section labeled "Quasi-standard" hints at the origin.
+
+ <B>o</B> NetBSD does not provide functions for enabling/disabling traces.
+ It uses environment variables <B>CURSES_TRACE_MASK</B> and <B>CURS-</B>
+ <B>ES_TRACE_FILE</B> to determine what is traced, and where the results
+ are written. This is available only when a debug-library is built.
+
+ The NetBSD tracing feature is undocumented.
+
+ A few ncurses functions are not provided when symbol versioning is
+ used: