delay_output, filter, flushinp, getwin, key_name, keyname, nofilter,
putwin, unctrl, use_env, use_tioctl, wunctrl - miscellaneous curses
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 rep‐
resentation of the character c, ignoring attributes. Control charac‐
ters are displayed in the ^X notation. Printing characters are dis‐
played as is. The corresponding wunctrl returns a printable represen‐
tation of a wide character.
The keyname routine returns a character string corresponding to the key
· Printable characters are displayed as themselves, e.g., a one-
character string containing the key.
· Control characters are displayed in the ^X notation.
· DEL (character 127) is displayed as ^?.
· Values above 128 are either meta characters (if the screen has
not been initialized, or if meta has been called with a TRUE pa‐
rameter), shown in the M-X notation, or are displayed as them‐
selves. In the latter case, the values may not be printable;
this follows the X/Open specification.
· Values above 256 may be the names of the names of function keys.
· Otherwise (if there is no corresponding name) the function re‐
turns null, to denote an error. X/Open also lists an "UNKNOWN
KEY" return value, which some implementations return rather than
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 effect 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 caller 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 information.
The use_env routine, if used, should be called before initscr or
newterm are called (because those compute the screen size). It modi‐
fies the way ncurses treats environment variables when determining the
· Normally ncurses looks first at the terminal database for the
If use_env was called with FALSE for parameter, it stops here un‐
less If use_tioctl was also called with TRUE for parameter.
· Then it asks for the screen size via operating system calls. If
successful, it overrides the values from the terminal database.
· 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 ter‐
Ncurses also updates the screen size in response to SIGWINCH, un‐
less 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 argument, ncurses modifies the
last step in its computation of screen size as follows:
· checks if the LINES and COLUMNS environment variables are set to a
number greater than zero.
· for each, ncurses updates the corresponding environment variable
with the value that it has obtained via operating system call or
from the terminal database.
· ncurses re-fetches the value of the environment variables so that
it is still the environment 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 new window.
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 speci‐
fied, 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 er‐
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 conditions. This implementation checks for
· the parameter is a 7-bit US-ASCII code. This is the case that
X/Open Curses documented.
· the parameter is in the range 128-159, i.e., a C1 control code.
If use_legacy_coding has been called with a 2 parameter, unctrl
returns the parameter, i.e., a one-character string with the pa‐
rameter 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 be‐
fore initializing curses. This implementation permits that, and
returns the ``~@'', etc., values in that case.
· parameter values outside the 0 to 255 range. unctrl returns a
The SVr4 documentation describes the action of filter only in the
vaguest terms. The description here is adapted from the XSI Curses
standard (which erroneously fails to describe 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 implementations have different conven‐
tions. 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
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 capa‐
bilities 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 description is read by
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 condi‐
tioned using NCURSES_VERSION.
SEE ALSOlegacy_coding(3X), curses(3X), curs_initscr(3X), curs_kernel(3X),
curs_scr_dump(3X), curs_variables(3X), legacy_coding(3X).