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Manual Pages  — curs_util


delay_output, filter, flushinp, getwin, key_name, keyname, nofilter, putwin, unctrl, use_env, use_tioctl, wunctrl - miscellaneous curses utility routines



#include <curses.h>

char *unctrl(chtype c);
wchar_t *wunctrl(cchar_t *c);
char *keyname(int c);
char *key_name(wchar_t w);
void filter(void);
void nofilter(void);
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);
int flushinp(void);


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:

» 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 parameter), shown in the M-X notation, or are displayed as themselves. 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 returns null, to denote an error. X/Open also lists an "UNKNOWN KEY" return value, which some implementations 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 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 modifies the way ncurses treats environment variables when determining the screen size.
» 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.
» 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 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 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:

This is the default behavior.
ncurses uses operating system calls
unless overridden by $LINES or $COLUMNS environment variables.
TRUETRUEncurses updates $LINES and $COLUMNS based on operating system calls.
FALSETRUEncurses ignores $LINES and $COLUMNS, uses operating system calls to obtain size.
FALSEFALSEncurses 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 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 conditions. This implementation checks for three cases:
» 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 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 that case.
» 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 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 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 description 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(3), curses(3), curs_initscr(3), curs_kernel(3), curs_scr_dump(3), curs_variables(3), legacy_coding(3).

curs_util (3X)

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