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<H1 class="no-header">curs_util 3x 2025-11-11 ncurses 6.6 Library calls</H1>
<PRE>
<STRONG><A HREF="curs_util.3x.html">curs_util(3x)</A></STRONG> Library calls <STRONG><A HREF="curs_util.3x.html">curs_util(3x)</A></STRONG>
</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
<STRONG>delay_output</STRONG>, <STRONG>filter</STRONG>, <STRONG>flushinp</STRONG>, <STRONG>getwin</STRONG>, <STRONG>key_name</STRONG>, <STRONG>keyname</STRONG>, <STRONG>nofilter</STRONG>,
<STRONG>putwin</STRONG>, <STRONG>unctrl</STRONG>, <STRONG>use_env</STRONG>, <STRONG>use_tioctl</STRONG>, <STRONG>wunctrl</STRONG> - miscellaneous <EM>curses</EM>
utility routines
</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
<STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
<STRONG>const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG> <STRONG>unctrl(chtype</STRONG> <EM>ch</EM><STRONG>);</STRONG>
<STRONG>wchar_t</STRONG> <STRONG>*</STRONG> <STRONG>wunctrl(cchar_t</STRONG> <STRONG>*</STRONG> <EM>wch</EM><STRONG>);</STRONG>
<STRONG>const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG> <STRONG>keyname(int</STRONG> <EM>c</EM><STRONG>);</STRONG>
<STRONG>const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG> <STRONG>key_name(wchar_t</STRONG> <EM>wc</EM><STRONG>);</STRONG>
<STRONG>void</STRONG> <STRONG>filter(void);</STRONG>
<EM>/*</EM> <EM>extension</EM> <EM>*/</EM>
<STRONG>void</STRONG> <STRONG>nofilter(void);</STRONG>
<STRONG>void</STRONG> <STRONG>use_env(bool</STRONG> <EM>bf</EM><STRONG>);</STRONG>
<EM>/*</EM> <EM>extension</EM> <EM>*/</EM>
<STRONG>void</STRONG> <STRONG>use_tioctl(bool</STRONG> <EM>bf</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>putwin(WINDOW</STRONG> <STRONG>*</STRONG> <EM>win</EM><STRONG>,</STRONG> <STRONG>FILE</STRONG> <STRONG>*</STRONG> <EM>filep</EM><STRONG>);</STRONG>
<STRONG>WINDOW</STRONG> <STRONG>*</STRONG> <STRONG>getwin(FILE</STRONG> <STRONG>*</STRONG> <EM>filep</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>delay_output(int</STRONG> <EM>ms</EM><STRONG>);</STRONG>
<STRONG>int</STRONG> <STRONG>flushinp(void);</STRONG>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
</PRE><H3><a name="h3-unctrl_wunctrl">unctrl, wunctrl</a></H3><PRE>
<STRONG>unctrl</STRONG> returns a null-terminated character string printably
representing the <EM>curses</EM> character <EM>ch</EM>, often one that originated in
keyboard input; see <STRONG><A HREF="curs_getch.3x.html">getch(3x)</A></STRONG>.
<STRONG>o</STRONG> Printable characters represent themselves as a one-character
string.
<STRONG>o</STRONG> Control characters are expressed in <STRONG>^</STRONG><EM>X</EM> notation, where <EM>X</EM> is the
printable symbol of the control code's value plus 32 in the
ISO 646/"ASCII" character set.
<STRONG>o</STRONG> DEL (character code 127) is represented as <STRONG>^?</STRONG>.
<STRONG>o</STRONG> A character code greater than 127 is represented in one of two
ways.
If the screen has not been initialized or is in meta mode (see
<STRONG><A HREF="curs_inopts.3x.html">meta(3x)</A></STRONG>), it is expressed in <STRONG>M-</STRONG><EM>X</EM> notation, where X is the
representation of the code's value minus 128, as described above.
If the screen is not in meta mode, the character code is assumed to
represent itself. It nevertheless may not be printable; this is
the case for character codes 128-159 in ISO 8859 encodings.
<EM>ncurses</EM>'s <STRONG><A HREF="legacy_coding.3x.html">use_legacy_coding(3x)</A></STRONG> function configures <STRONG>unctrl</STRONG>'s
handling of these character codes.
<STRONG>wunctrl</STRONG> returns a null-terminated wide-character string printably
representing the <EM>curses</EM> complex character <EM>wch</EM>.
Both functions ignore the attributes and color pair selection of their
argument.
</PRE><H3><a name="h3-keyname_key_name">keyname, key_name</a></H3><PRE>
The <STRONG>keyname</STRONG> routine returns a character string corresponding to the key
<EM>c</EM>. Key codes are different from character codes.
<STRONG>o</STRONG> Key codes below 256 are characters. They are displayed using
<STRONG>unctrl</STRONG>.
<STRONG>o</STRONG> Values above 256 may be the codes for function keys. The function
key name is displayed.
<STRONG>o</STRONG> Otherwise (if there is no corresponding name and the key is not a
character) the function returns null, to denote an error. X/Open
also lists an "UNKNOWN KEY" return value, which some
implementations return rather than null.
The corresponding <STRONG>key_name</STRONG> returns a multibyte character string
corresponding to the wide-character value <EM>wc</EM>. The two functions
(<STRONG>keyname</STRONG> and <STRONG>key_name</STRONG>) do not return the same set of strings:
<STRONG>o</STRONG> <STRONG>keyname</STRONG> returns null where <STRONG>key_name</STRONG> would display a meta character.
<STRONG>o</STRONG> <STRONG>key_name</STRONG> does not return the name of a function key.
</PRE><H3><a name="h3-filter_nofilter">filter, nofilter</a></H3><PRE>
The <STRONG>filter</STRONG> routine, if used, must be called before <STRONG>initscr</STRONG> or <STRONG>newterm</STRONG>
are called. Calling <STRONG>filter</STRONG> causes these changes in initialization:
<STRONG>o</STRONG> <STRONG>LINES</STRONG> is set to 1;
<STRONG>o</STRONG> the capabilities <STRONG>clear</STRONG>, <STRONG>cud1</STRONG>, <STRONG>cud</STRONG>, <STRONG>cup</STRONG>, <STRONG>cuu1</STRONG>, <STRONG>cuu</STRONG>, <STRONG>vpa</STRONG> are
disabled;
<STRONG>o</STRONG> the capability <STRONG>ed</STRONG> is disabled if <STRONG>bce</STRONG> is set;
<STRONG>o</STRONG> and the <STRONG>home</STRONG> string is set to the value of <STRONG>cr</STRONG>.
The <STRONG>nofilter</STRONG> routine cancels the effect of a preceding <STRONG>filter</STRONG> call.
That allows the caller to initialize a screen on a different device,
using a different value of <STRONG>$TERM</STRONG>. The limitation arises because the
<STRONG>filter</STRONG> routine modifies the in-memory copy of the terminal information.
</PRE><H3><a name="h3-use_env">use_env</a></H3><PRE>
The <STRONG>use_env</STRONG> routine, if used, should be called before <STRONG>initscr</STRONG> or
<STRONG>newterm</STRONG> are called (because those compute the screen size). It
modifies the way <EM>ncurses</EM> treats environment variables when determining
the screen size.
<STRONG>o</STRONG> Normally <EM>ncurses</EM> looks first at the terminal database for the
screen size.
If <STRONG>use_env</STRONG> was called with <STRONG>FALSE</STRONG> for parameter, it stops here
unless <STRONG>use_tioctl</STRONG> was also called with <STRONG>TRUE</STRONG> for parameter.
<STRONG>o</STRONG> Then it asks for the screen size via operating system calls. If
successful, it overrides the values from the terminal database.
<STRONG>o</STRONG> Finally (unless <STRONG>use_env</STRONG> was called with <STRONG>FALSE</STRONG> parameter), <EM>ncurses</EM>
examines the <EM>LINES</EM> or <EM>COLUMNS</EM> environment variables, using a value
in those to override the results from the operating system or
terminal database.
<EM>curses</EM> also updates the screen size in response to <EM>SIGWINCH</EM>, unless
overridden by the <EM>LINES</EM> or <EM>COLUMNS</EM> environment variables,
</PRE><H3><a name="h3-use_tioctl">use_tioctl</a></H3><PRE>
The <STRONG>use_tioctl</STRONG> routine, if used, should be called before <STRONG>initscr</STRONG> or
<STRONG>newterm</STRONG> are called (because those compute the screen size). After
<STRONG>use_tioctl</STRONG> is called with <STRONG>TRUE</STRONG> as an argument, <EM>ncurses</EM> modifies the
last step in its computation of screen size as follows:
<STRONG>o</STRONG> checks whether the <EM>LINES</EM> and <EM>COLUMNS</EM> environment variables are set
to a number greater than zero.
<STRONG>o</STRONG> for each, <EM>ncurses</EM> updates the corresponding environment variable
with the value that it has obtained via operating system call or
from the terminal database.
<STRONG>o</STRONG> <EM>ncurses</EM> re-fetches the value of the environment variables so that
it is still the environment variables that set the screen size.
The <STRONG>use_env</STRONG> and <STRONG>use_tioctl</STRONG> routines combine as follows.
<STRONG>use_env</STRONG> <STRONG>use_tioctl</STRONG> <STRONG>Summary</STRONG>
-----------------------------------------------------------------
<STRONG>TRUE</STRONG> <STRONG>FALSE</STRONG> <EM>ncurses</EM> uses operating system calls
unless overridden by <EM>LINES</EM> or <EM>COLUMNS</EM>
environment variables; default.
<STRONG>TRUE</STRONG> <STRONG>TRUE</STRONG> <EM>ncurses</EM> updates <EM>LINES</EM> and <EM>COLUMNS</EM> based
on operating system calls.
<STRONG>FALSE</STRONG> <STRONG>TRUE</STRONG> <EM>ncurses</EM> ignores <EM>LINES</EM> and <EM>COLUMNS</EM>, using
operating system calls to obtain size.
</PRE><H3><a name="h3-putwin_getwin">putwin, getwin</a></H3><PRE>
The <STRONG>putwin</STRONG> routine writes all data associated with window (or pad) <EM>win</EM>
into the file to which <EM>filep</EM> points. This information can be later
retrieved using the <STRONG>getwin</STRONG> function.
The <STRONG>getwin</STRONG> routine reads window related data stored in the file by
<STRONG>putwin</STRONG>. The routine then creates and initializes a new window using
that data. It returns a pointer to the new window. There are a few
caveats:
<STRONG>o</STRONG> the data written is a copy of the <EM>WINDOW</EM> structure, and its
associated character cells. The format differs between the wide-
character (<EM>ncursesw</EM>) and non-wide (<EM>ncurses</EM>) libraries. You can
transfer data between the two, however.
<STRONG>o</STRONG> the retrieved window is always created as a top-level window (or
pad), rather than a subwindow.
<STRONG>o</STRONG> the window's character cells contain the color pair <EM>value</EM>, but not
the actual color <EM>numbers</EM>. If cells in the retrieved window use
color pairs that have not been created in the application using
<STRONG>init_pair</STRONG>, they will not be colored when the window is refreshed.
</PRE><H3><a name="h3-delay_output">delay_output</a></H3><PRE>
The <STRONG>delay_output</STRONG> routine inserts an <EM>ms</EM> millisecond pause in output.
Employ this function judiciously when terminal output uses padding,
because <EM>ncurses</EM> transmits null characters (consuming CPU and I/O
resources) instead of sleeping and requesting resumption from the
operating system. Padding is used unless:
<STRONG>o</STRONG> the terminal description has <STRONG>npc</STRONG> (<STRONG>no_pad_char</STRONG>) capability, or
<STRONG>o</STRONG> the environment variable <STRONG>NCURSES_NO_PADDING</STRONG> is set.
If padding is not in use, <EM>ncurses</EM> uses <STRONG>napms</STRONG> to perform the delay. If
the value of <EM>ms</EM> exceeds 30,000 (thirty seconds), it is capped at that
value.
</PRE><H3><a name="h3-flushinp">flushinp</a></H3><PRE>
The <STRONG>flushinp</STRONG> routine throws away any typeahead that has been typed by
the user and has not yet been read by the program.
</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
Except for <STRONG>flushinp</STRONG>, functions that return integers return <STRONG>ERR</STRONG> upon
failure and <STRONG>OK</STRONG> upon success.
Functions that return pointers return a null pointer on failure.
In <EM>ncurses</EM>,
<STRONG>o</STRONG> <STRONG>flushinp</STRONG> returns <STRONG>ERR</STRONG> if the terminal was not initialized, and
<STRONG>o</STRONG> <STRONG>putwin</STRONG> returns <STRONG>ERR</STRONG> if its associated <STRONG>write(2)</STRONG> calls return <STRONG>ERR</STRONG>.
</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
<STRONG>wunctrl</STRONG> is part of <EM>ncurses</EM>'s wide-character API, and is not available
in its non-wide-character configuration.
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
X/Open Curses Issue 4 describes these functions. It specifies no error
conditions for them.
SVr4 describes a successful return value only as "an integer value
other than <EM>ERR</EM>".
</PRE><H3><a name="h3-filter">filter</a></H3><PRE>
The SVr4 documentation describes the action of <STRONG>filter</STRONG> only in the
vaguest terms. The description here is adapted from X/Open Curses
(which erroneously fails to describe the disabling of <STRONG>cuu</STRONG>).
</PRE><H3><a name="h3-delay_output-padding">delay_output padding</a></H3><PRE>
The limitation to 30 seconds and the use of <STRONG>napms</STRONG> differ from other
implementations.
<STRONG>o</STRONG> SVr4 <EM>curses</EM> does not delay if no padding character is available.
<STRONG>o</STRONG> NetBSD <EM>curses</EM> uses <STRONG>napms</STRONG> when no padding character is available,
but does not take timing into account when using the padding
character.
Neither limits the delay.
</PRE><H3><a name="h3-keyname">keyname</a></H3><PRE>
The <STRONG>keyname</STRONG> function may return the names of user-defined string
capabilities that are defined in the terminfo entry via the <STRONG>-x</STRONG> option
of <STRONG>tic</STRONG>. This implementation automatically assigns at run-time key
codes to user-defined strings that begin with "k". The key codes start
at KEY_MAX, but are not guaranteed to be the same value for different
runs because user-defined codes are merged from all terminal
descriptions that have been loaded. The <STRONG><A HREF="curs_extend.3x.html">use_extended_names(3x)</A></STRONG>
function controls whether this data is loaded when the terminal
description is read by the library.
</PRE><H3><a name="h3-nofilter_use_tioctl">nofilter, use_tioctl</a></H3><PRE>
The <STRONG>nofilter</STRONG> and <STRONG>use_tioctl</STRONG> routines are specific to <EM>ncurses</EM>. They
were not supported on Version 7, BSD or System V implementations. It
is recommended that any code depending on <EM>ncurses</EM> extensions be
conditioned using <STRONG>NCURSES_VERSION</STRONG>.
</PRE><H3><a name="h3-putwin_getwin-file-format">putwin/getwin file-format</a></H3><PRE>
The <STRONG>putwin</STRONG> and <STRONG>getwin</STRONG> functions have several issues with portability:
<STRONG>o</STRONG> The files written and read by these functions use an
implementation-specific format. Although the format is an obvious
target for standardization, it has been overlooked.
Interestingly enough, according to the copyright dates in Solaris
source, the functions (along with <STRONG>scr_init</STRONG>, etc.) originated with
the University of California, Berkeley (in 1982) and were later (in
1988) incorporated into SVr4. Oddly, there are no such functions
in the 4.3BSD <EM>curses</EM> sources.
<STRONG>o</STRONG> Most implementations simply dump the binary <EM>WINDOW</EM> structure to the
file. These include SVr4 <EM>curses</EM>, NetBSD <EM>curses</EM>, and <EM>PDCurses</EM>, as
well as older <EM>ncurses</EM> versions. This implementation (as well as
<EM>xcurses</EM>, the X/Open variant of Solaris <EM>curses</EM>, dated 1995) uses
textual dumps.
The implementations that use binary dumps use block I/O (<STRONG>write(2)</STRONG>
and <STRONG>read(2)</STRONG> functions). Those that use textual dumps use buffered
I/O. A few applications may happen to write extra data in the file
using these functions. Doing that can run into problems mixing
block and buffered I/O. This implementation reduces the problem on
writes by flushing the output. However, reading from a file
written using mixed schemes may not be successful.
</PRE><H3><a name="h3-unctrl_wunctrl">unctrl, wunctrl</a></H3><PRE>
X/Open Curses Issue 4 describes these functions. It specifies no error
conditions for them. It states that <STRONG>unctrl</STRONG> and <STRONG>wunctrl</STRONG> will return a
null pointer if unsuccessful. This implementation checks for three
cases:
<STRONG>o</STRONG> the parameter is a 7-bit US-ASCII code. This is the case that
X/Open Curses documented.
<STRONG>o</STRONG> the parameter is in the range 128-159, i.e., a C1 control code. If
<STRONG><A HREF="legacy_coding.3x.html">use_legacy_coding(3x)</A></STRONG> has been called with a <STRONG>2</STRONG> parameter, <STRONG>unctrl</STRONG>
returns the parameter, i.e., a one-character string with the
parameter as the first character. Otherwise, it returns "~@",
"~A", etc., analogous to "^@", "^A", C0 controls.
X/Open Curses does not document whether <STRONG>unctrl</STRONG> can be called before
initializing <EM>curses</EM>. This implementation permits that, and returns
the "~@", etc., values in that case.
<STRONG>o</STRONG> parameter values outside the 0 to 255 range. <STRONG>unctrl</STRONG> returns a null
pointer.
The strings returned by <STRONG>unctrl</STRONG> in this implementation are determined at
compile time, showing C1 controls from the upper-128 codes with a "~"
prefix rather than "^". Other implementations have different
conventions. For example, they may show both sets of control
characters with "^", and strip the parameter to 7 bits. Or they may
ignore C1 controls and treat all of the upper-128 codes as printable.
This implementation uses 8 bits but does not modify the string to
reflect locale. The <STRONG><A HREF="legacy_coding.3x.html">use_legacy_coding(3x)</A></STRONG> function allows the caller
to change the output of <STRONG>unctrl</STRONG>.
Likewise, the <STRONG><A HREF="curs_inopts.3x.html">meta(3x)</A></STRONG> function allows the caller to change the output
of <STRONG>keyname</STRONG>, i.e., it determines whether to use the "M-" prefix for
"meta" keys (codes in the range 128 to 255). Both
<STRONG><A HREF="legacy_coding.3x.html">use_legacy_coding(3x)</A></STRONG> and <STRONG><A HREF="curs_inopts.3x.html">meta(3x)</A></STRONG> succeed only after <EM>curses</EM> is
initialized. X/Open Curses does not document the treatment of codes
128 to 159. When treating them as "meta" keys (or if <STRONG>keyname</STRONG> is called
before initializing <EM>curses</EM>), this implementation returns strings
"M-^@", "M-^A", etc.
X/Open Curses documents <EM>unctrl</EM> as declared in <EM>unctrl.h</EM>, which <EM>ncurses</EM>
does. However, <EM>ncurses</EM>'s <EM>curses.h</EM> includes <EM>unctrl.h</EM>, matching the
behavior of SVr4 <EM>curses</EM>. Other implementations may not do that.
</PRE><H3><a name="h3-use_env_use_tioctl">use_env, use_tioctl</a></H3><PRE>
If <EM>ncurses</EM> is configured to provide the sp-functions extension, the
state of <STRONG>use_env</STRONG> and <STRONG>use_tioctl</STRONG> may be updated before creating each
<EM>screen</EM> rather than once only (<STRONG><A HREF="curs_sp_funcs.3x.html">curs_sp_funcs(3x)</A></STRONG>). This feature of
<STRONG>use_env</STRONG> is not provided by other implementations of <EM>curses</EM>.
</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
4BSD (1980) introduced <EM>unctrl</EM>, defining it as a macro in <EM>unctrl.h</EM>.
SVr2 (1984) added <EM>delay</EM><STRONG>_</STRONG><EM>output</EM>, <EM>flushinp</EM>, and <EM>keyname</EM>.
SVr3 (1987) supplied <EM>filter</EM>. Later that year, SVr3.1 brought <EM>getwin</EM>
and <EM>putwin</EM>, reading and writing window dumps with <STRONG>fread(3)</STRONG> and
<STRONG>fwrite(3)</STRONG>, respectively.
SVr4 (1989) furnished <EM>use</EM><STRONG>_</STRONG><EM>env</EM>.
X/Open Curses Issue 4 (1995) specified <EM>key</EM><STRONG>_</STRONG><EM>name</EM> and <EM>wunctrl</EM>.
<EM>ncurses</EM> 5.6 (2006) added <EM>nofilter</EM>, and 6.0 (2015) <EM>use</EM><STRONG>_</STRONG><EM>tioctl</EM>.
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
<STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>, <STRONG><A HREF="curs_inopts.3x.html">curs_inopts(3x)</A></STRONG>, <STRONG><A HREF="curs_kernel.3x.html">curs_kernel(3x)</A></STRONG>,
<STRONG><A HREF="curs_scr_dump.3x.html">curs_scr_dump(3x)</A></STRONG>, <STRONG><A HREF="curs_sp_funcs.3x.html">curs_sp_funcs(3x)</A></STRONG>, <STRONG><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>,
<STRONG><A HREF="legacy_coding.3x.html">legacy_coding(3x)</A></STRONG>
ncurses 6.6 2025-11-11 <STRONG><A HREF="curs_util.3x.html">curs_util(3x)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a href="#h3-unctrl_wunctrl">unctrl, wunctrl</a></li>
<li><a href="#h3-keyname_key_name">keyname, key_name</a></li>
<li><a href="#h3-filter_nofilter">filter, nofilter</a></li>
<li><a href="#h3-use_env">use_env</a></li>
<li><a href="#h3-use_tioctl">use_tioctl</a></li>
<li><a href="#h3-putwin_getwin">putwin, getwin</a></li>
<li><a href="#h3-delay_output">delay_output</a></li>
<li><a href="#h3-flushinp">flushinp</a></li>
</ul>
</li>
<li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
<li><a href="#h2-NOTES">NOTES</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a>
<ul>
<li><a href="#h3-filter">filter</a></li>
<li><a href="#h3-delay_output-padding">delay_output padding</a></li>
<li><a href="#h3-keyname">keyname</a></li>
<li><a href="#h3-nofilter_use_tioctl">nofilter, use_tioctl</a></li>
<li><a href="#h3-putwin_getwin-file-format">putwin/getwin file-format</a></li>
<li><a href="#h3-unctrl_wunctrl">unctrl, wunctrl</a></li>
<li><a href="#h3-use_env_use_tioctl">use_env, use_tioctl</a></li>
</ul>
</li>
<li><a href="#h2-HISTORY">HISTORY</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
</div>
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