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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ENVIRONMENT | PORTABILITY | SEE ALSO | COLOPHON |
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curs_trace(3X) Library calls curs_trace(3X)
curses_trace, trace, _tracef, _traceattr, _traceattr2,
_tracecchar_t, _tracecchar_t2, _tracechar, _tracechtype,
_tracechtype2, _nc_tracebits, _tracedump, _tracemouse - curses
debugging routines
#include <curses.h>
unsigned curses_trace(const unsigned trace-mask);
void _tracef(const char *format, ...);
char *_traceattr(attr_t attr);
char *_traceattr2(int buffer, chtype ch);
char *_tracecchar_t(const cchar_t *string);
char *_tracecchar_t2(int buffer, const cchar_t *string);
char *_tracechar(int c);
char *_tracechtype(chtype ch);
char *_tracechtype2(int buffer, chtype ch);
void _tracedump(const char *label, WINDOW *win);
char *_nc_tracebits(void);
char *_tracemouse(const MEVENT *event);
/* deprecated */
void trace(const unsigned int trace-mask);
The curses trace routines are used for debugging the ncurses
libraries, as well as applications which use the ncurses
libraries. Some limitations apply:
• Aside from curses_trace, the other functions are normally
available only with the debugging library e.g.,
libncurses_g.a.
All of the trace functions may be compiled into any model
(shared, static, profile) by defining the symbol TRACE.
• Additionally, the functions which use cchar_t are only
available with the wide-character configuration of the
libraries.
Functions
The principal parts of this interface are
• curses_trace, which selectively enables different tracing
features, and
• _tracef, which writes formatted data to the trace file.
The other functions either return a pointer to a string-area
(allocated by the corresponding function), or return no value
(such as _tracedump, which implements the screen dump for
TRACE_UPDATE). The caller should not free these strings,
since the allocation is reused on successive calls. To work
around the problem of a single string-area per function, some
use a buffer-number parameter, telling the library to allocate
additional string-areas.
The curses_trace function is always available, whether or not the
other trace functions are available:
• If tracing is available, calling curses_trace with a nonzero
parameter updates the trace mask, and returns the previous
trace mask.
When the trace mask is nonzero, ncurses creates the file
“trace” in the current directory for output. If the file
already exists, no tracing is done.
• If tracing is not available, curses_trace returns zero (0).
Trace Parameter
The trace parameter is formed by logically “or”-ing values from
the list of TRACE_xxx definitions in <curses.h>. These include:
TRACE_DISABLE
turn off tracing by passing a zero parameter.
The library flushes the output file, but retains an open
file-descriptor to the trace file so that it can resume
tracing later if a nonzero parameter is passed to the
curses_trace function.
TRACE_TIMES
trace user and system times of updates.
TRACE_TPUTS
trace tputs(3X) calls.
TRACE_UPDATE
trace update actions, old & new screens.
TRACE_MOVE
trace cursor movement and scrolling.
TRACE_CHARPUT
trace all character outputs.
TRACE_ORDINARY
trace all update actions. The old and new screen contents
are written to the trace file for each refresh.
TRACE_CALLS
trace all curses calls. The parameters for each call are
traced, as well as return values.
TRACE_VIRTPUT
trace virtual character puts, i.e., calls to addch.
TRACE_IEVENT
trace low-level input processing, including timeouts.
TRACE_BITS
trace state of TTY control bits.
TRACE_ICALLS
trace internal/nested calls.
TRACE_CCALLS
trace per-character calls.
TRACE_DATABASE
trace read/write of terminfo/termcap data.
TRACE_ATTRS
trace changes to video attributes and colors.
TRACE_MAXIMUM
maximum trace level, enables all of the separate trace
features.
Some tracing features are enabled whenever the curses_trace
parameter is nonzero. Some features overlap. The specific names
are used as a guideline.
Command-line Utilities
The command-line utilities such as tic(1) provide a verbose option
which extends the set of messages written using the curses_trace
function. Both of these (-v and curses_trace) use the same
variable (_nc_tracing), which determines the messages which are
written.
Because the command-line utilities may call initialization
functions such as setupterm, tgetent or use_extended_names, some
of their debugging output may be directed to the trace file if the
NCURSES_TRACE environment variable is set:
• messages produced in the utility are written to the standard
error.
• messages produced by the underlying library are written to
trace.
If ncurses is built without tracing, none of the latter are
produced, and fewer diagnostics are provided by the command-line
utilities.
Routines which return a value are designed to be used as
parameters to the _tracef routine.
NCURSES_TRACE
A positive integral value stored in this variable causes the
following functions to enable the tracing feature as if
curses_trace were called.
filter, initscr, new_prescr, newterm, nofilter, restartterm,
ripoffline, setupterm, slk_init, tgetent, use_env,
use_extended_names, use_tioctl
These functions are not part of the X/Open Curses interface. Some
other curses implementations are known to have similar features,
but they are not compatible with ncurses:
• SVr4 provided traceon and traceoff, to control whether
debugging information was written to the “trace” file. While
the functions were always available, this feature was only
enabled if DEBUG was defined when building the library.
The SVr4 tracing feature is undocumented.
• PDCurses provides traceon and traceoff, which (like SVr4) are
always 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.
• NetBSD does not provide functions for enabling/disabling
traces. It uses environment variables CURSES_TRACE_MASK and
CURSES_TRACE_FILE 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:
_nc_tracebits, _tracedump, _tracemouse
The original trace routine was deprecated because it often
conflicted with application names.
curses(3X)
This page is part of the ncurses (new curses) project.
Information about the project can be found at
⟨https://invisible-island.net/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to bug-ncurses@gnu.org.
This page was obtained from the tarball ncurses-6.6.tar.gz fetched
from ⟨https://ftp.gnu.org/gnu/ncurses/⟩ on 2026-01-16. 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
ncurses @NCURSES_MAJOR@.@NCU... 2025-01-18 curs_trace(3X)
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HTML rendering created 2026-01-16 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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