delay_output, filter, flushinp, getwin, key_name, keyname, nofilter, putwin, unctrl,
use_env, use_tioctl, wunctrl - miscellaneous curses utility routines
char *unctrl(chtype c);
wchar_t *wunctrl(cchar_t *c);
char *keyname(int c);
char *key_name(wchar_t w);
void use_env(bool f);
void use_tioctl(bool f);
int putwin(WINDOW *win, FILE *filep);
WINDOW *getwin(FILE *filep);
int delay_output(int ms);
The unctrl routine returns a character string which is a printable representation of the
character c, ignoring attributes. Control characters are displayed in the ^X notation.
Printing characters are displayed as is. The corresponding wunctrl returns a printable
representation of a wide character.
The keyname routine returns a character string corresponding to the key c:
o Printable characters are displayed as themselves, e.g., a one-character string con-
taining the key.
o Control characters are displayed in the ^X notation.
o DEL (character 127) is displayed as ^?.
o Values above 128 are either meta characters (if the screen has not been initial-
ized, or if meta has been called with a TRUE parameter), shown in the M-X notation,
or are displayed as themselves. In the latter case, the values may not be print-
able; this follows the X/Open specification.
o Values above 256 may be the names of the names of function keys.
o Otherwise (if there is no corresponding name) the function returns null, to denote
an error. X/Open also lists an "UNKNOWN KEY" return value, which some implementa-
tions return rather than null.
The corresponding key_name returns a character string corresponding to the wide-character
value w. The two functions do not return the same set of strings; the latter returns null
where the former would display a meta character.
The filter routine, if used, must be called before initscr or newterm are called. The ef-
fect is that, during those calls, LINES is set to 1; the capabilities clear, cup, cud,
cud1, cuu1, cuu, vpa are disabled; and the home string is set to the value of cr.
The nofilter routine cancels the effect of a preceding filter call. That allows the call-
er to initialize a screen on a different device, using a different value of $TERM. The
limitation arises because the filter routine modifies the in-memory copy of the terminal
The use_env routine, if used, should be called before initscr or newterm are called (be-
cause those compute the screen size). It modifies the way ncurses treats environment
variables when determining the screen size.
o Normally ncurses looks first at the terminal database for the screen size.
If use_env was called with FALSE for parameter, it stops here unless If use_tioctl was
also called with TRUE for parameter.
o Then it asks for the screen size via operating system calls. If successful, it over-
rides the values from the terminal database.
o Finally (unless use_env was called with FALSE parameter), ncurses examines the LINES
or COLUMNS environment variables, using a value in those to override the results from
the operating system or terminal database.
Ncurses also updates the screen size in response to SIGWINCH, unless overridden by the
LINES or COLUMNS environment variables,
The use_tioctl routine, if used, should be called before initscr or newterm are called
(because those compute the screen size). After use_tioctl is called with TRUE as an argu-
ment, ncurses modifies the last step in its computation of screen size as follows:
o checks if the LINES and COLUMNS environment variables are set to a number greater than
o for each, ncurses updates the corresponding environment variable with the value that
it has obtained via operating system call or from the terminal database.
o ncurses re-fetches the value of the environment variables so that it is still the en-
vironment variables which set the screen size.
The use_env and use_tioctl routines combine as summarized here:
use_env use_tioctl Summary
TRUE FALSE This is the default behavior. ncurses
uses operating system calls unless over-
ridden by $LINES or $COLUMNS environment
TRUE TRUE ncurses updates $LINES and $COLUMNS
based on operating system calls.
FALSE TRUE ncurses ignores $LINES and $COLUMNS, us-
es operating system calls to obtain
FALSE FALSE ncurses relies on the terminal database
to determine size.
The putwin routine writes all data associated with window win into the file to which filep
points. This information can be later retrieved using the getwin function.
The getwin routine reads window related data stored in the file by putwin. The routine
then creates and initializes a new window using that data. It returns a pointer to the
The delay_output routine inserts an ms millisecond pause in output. This routine should
not be used extensively because padding characters are used rather than a CPU pause. If
no padding character is specified, this uses napms to perform the delay.
The flushinp routine throws away any typeahead that has been typed by the user and has not
yet been read by the program.
Except for flushinp, routines that return an integer return ERR upon failure and OK (SVr4
specifies only "an integer value other than ERR") upon successful completion.
Routines that return pointers return NULL on error.
X/Open does not define any error conditions. In this implementation
returns an error if the terminal was not initialized.
meta returns an error if the terminal was not initialized.
returns an error if the associated fwrite calls return an error.
The XSI Curses standard, Issue 4 describes these functions. It states that unctrl and
wunctrl will return a null pointer if unsuccessful, but does not define any error condi-
tions. This implementation checks for three cases:
o the parameter is a 7-bit US-ASCII code. This is the case that X/Open Curses docu-
o the parameter is in the range 128-159, i.e., a C1 control code. If use_legacy_cod-
ing has been called with a 2 parameter, unctrl 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 unctrl can be called before initializing
curses. This implementation permits that, and returns the ``~@'', etc., values in
o parameter values outside the 0 to 255 range. unctrl returns a null pointer.
The SVr4 documentation describes the action of filter only in the vaguest terms. The de-
scription here is adapted from the XSI Curses standard (which erroneously fails to de-
scribe the disabling of cuu).
The strings returned by unctrl in this implementation are determined at compile time,
showing C1 controls from the upper-128 codes with a `~' prefix rather than `^'. Other im-
plementations 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 use_legacy_coding function allows the
caller to change the output of unctrl.
Likewise, the meta function allows the caller to change the output of keyname, i.e., it
determines whether to use the `M-' prefix for ``meta'' keys (codes in the range 128 to
255). Both use_legacy_coding and meta succeed only after curses is initialized. X/Open
Curses does not document the treatment of codes 128 to 159. When treating them as
``meta'' keys (or if keyname is called before initializing curses), this implementation
returns strings ``M-^@'', ``M-^A'', etc.
The keyname function may return the names of user-defined string capabilities which are
defined in the terminfo entry via the -x option of tic. This implementation automatically
assigns at run-time keycodes to user-defined strings which begin with "k". The keycodes
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 which have been loaded. The
use_extended_names function controls whether this data is loaded when the terminal de-
scription is read by the library.
The nofilter and use_tioctl routines are specific to ncurses. They were not supported on
Version 7, BSD or System V implementations. It is recommended that any code depending on
ncurses extensions be conditioned using NCURSES_VERSION.
legacy_coding(3X), curses(3X), curs_initscr(3X), curs_kernel(3X), curs_scr_dump(3X),