NAME

curses_input, getch, wgetch, mvgetch, mvwgetch, define_key, keyok, has_key, getnstr, wgetnstr, mvgetnstr, mvwgetnstr, getstr, wgetstr, mvgetstr, mvwgetstr, keypad, is_keypad, notimeout, timeout, wtimeout, nodelay, ungetch, set_escdelay — curses input stream routines

LIBRARY

Curses Library (libcurses, -lcurses)

SYNOPSIS

#include <curses.h>

int
getch(void);

int
wgetch(WINDOW *win);

int
mvgetch(int y, int x);

int
mvwgetch(WINDOW *win, int y, int x);

int
keyok(int key_symbol, bool flag);

int
has_key(int key_symbol);

int
define_key(char *sequence, int key_symbol);

int
getnstr(char *str, int limit);

int
wgetnstr(WINDOW *win, char *str, int limit);

int
mvgetnstr(int y, int x, char *str, int limit);

int
mvwgetnstr(WINDOW *win, int y, int x, char *str, int limit);

int
getstr(char *str);

int
wgetstr(WINDOW *win, char *str);

int
mvgetstr(int y, int x, char *str);

int
mvwgetstr(WINDOW *win, int y, int x, char *str);

int
keypad(WINDOW *win, boolf flag);

bool
is_keypad(const WINDOW *win);

int
notimeout(WINDOW *win, boolf flag);

int
timeout(int delay);

int
wtimeout(WINDOW *win, int delay);

int
nodelay(WINDOW *win, boolf flag);

int
ungetch(int c);

int
set_escdelay(int escdelay);

extern int ESCDELAY;

DESCRIPTION

These functions read characters and strings from the window input file descriptor.

The getch() function reads a character from the stdscr input file descriptor and returns it. If the keypad() flag has been set to TRUE, then getch() will assemble multi-character key sequences into key symbols, If the terminal is resized, getch() will return KEY_RESIZE, regardless of the setting of keypad(). Calling getch() will cause an implicit refresh() on stdscr.

The wgetch() function is the same as the getch() function, excepting that it reads from the input file descriptor associated with the window specified by win.

If the keypad() flag is TRUE then the assembly of specific key symbols can be disabled by using the keyok() function. If the flag is set to FALSE on a key symbol then getch() will behave as if the character sequence associated with that key symbol was not recognised and will return the component characters one at a time to the caller. The is_keypad() function returns TRUE if the keypad flag is set for the window specified by win.

The has_key() function takes a key value and returns TRUE if the current terminal recognises a key with that value, otherwise FALSE.

Custom associations between sequences of characters and a key symbol can be made by using the define_key() function. Normally, these associations are made by the information in the terminfo(5) database but the define_key() function gives the capability to remove or add more associations. If define_key() is passed a non-NULL string in sequence it will associate that sequence with the key symbol passed in key_symbol. The key symbol may be one of the ones listed below or a custom value that is application defined. It is valid to have multiple character sequences map to the same key symbol and there are no constraints on the length of the sequence allowed. The assembly of custom sequences follow the same rules for inter-character timing and so forth as the terminfo(5) derived ones. If define_key() is passed a NULL in sequence then all associations for the key symbol in key_symbol will be deleted, this includes any associations that were derived from terminfo(5).

The mvgetch() and mvwgetch() functions are the same as the getch() and wgetch() functions, respectively, excepting that wmove() is called to move the cursor to the position specified by y, x before the character is read.

Calling getnstr(), wgetnstr(), mvgetnstr() or mvwgetnstr() is effectively the same as calling getch() repeatedly until a newline is received or the character limit limit is reached. Once this happens the string is NULL terminated and returned in str. During input, the normal curses input key processing is performed and affects the input buffer. The mvgetnstr() function calls wmove() to move the cursor to the position given by y, x before getting the string, wgetnstr() reads the input from the designated window, mvwgetnstr() moves the cursor to the position given by y, x before getting the input from the designated window.

The functions getstr(), wgetstr(), mvgetstr(), and mvwgetstr() are similar to getnstr(), wgetnstr(), mvgetnstr(), and mvwgetnstr(), respectively, excepting that there is no limit on the number of characters that may be inserted into str. This may cause the buffer to be overflowed, so their use is not recommended.

The keypad() function is used to affect how getch() processes input characters. If flag is set to TRUE, then getch() will scan the input stream looking for multi-character key sequences that are emitted by some terminal function keys. If a recognised sequence of characters is found, then getch() will collapse that sequence into an integer key symbol, as shown below. The default setting for the flag is FALSE.

The notimeout() function controls whether or not getch() will wait indefinitely between characters in a multi-character key sequence or not. If flag is TRUE, then there is no timeout applied between characters comprising a multi-character key sequence. If flag is FALSE, then the component characters of a multi-character sequence must not have an inter-character gap of more than ESCDELAY. If this timing is exceeded, then the multi-character key assembly is deemed to have failed and the characters read thus far are returned one at a time when getch() is called. The default setting for the flag is FALSE. The default value of ESCDELAY is 300ms. If ESCDELAY is negative, no timeout is applied between characters comprising a multi-character key sequence.

The timeout() function affects the behaviour of getch() when reading a character from stdscr. If delay is negative, then getch() will block indefinitely on a read. If delay is 0, then getch() will return immediately with ERR if there are no characters immediately available. If delay is a positive number, then getch() will wait for that many milliseconds before returning and, if no character was available, then ERR will be returned. Note that for a positive number, the timeout is only accurate to the nearest tenth of a second. Also, the maximum value of delay is 25500 milliseconds. The wtimeout() function does the same as timeout() but applies to the specified window win.

The nodelay() function turns on and off blocking reads for getch(). If flag is TRUE, then getch() will not block on reads, if flag is FALSE, then reads will block. The default setting for the flag is FALSE. nodelay(win, TRUE) is equivalent to wtimeout(win, 0) and nodelay(win, FALSE) is equivalent to wtimeout(win, -1).

ungetch() will convert c into an unsigned char and push that character back onto the input stream. Only one character of push-back is guaranteed to work, more may be possible depending on system resources.

The set_escdelay() function sets the ESCDELAY value of the current screen to escdelay.

RETURN VALUES

The functions getch(), wgetch(), mvgetch(), and mvwgetch() will return the value of the key pressed or ERR in the case of an error or a timeout. Additionally, if keypad(TRUE) has been called on a window, then it may return one of the following values:

Note that not all terminals are capable of generating all the keycodes listed above nor are terminfo entries normally configured with all the above capabilities defined.

Other functions that return an int will return one of the following values:

OK

The function completed successfully.

ERR

An error occurred in the function.

Functions returning pointers will return NULL if an error is detected.

SEE ALSO

curses_cursor(3), curses_keyname(3), curses_refresh(3), curses_tty(3), terminfo(5)

STANDARDS

The NetBSD Curses library complies with the X/Open Curses specification, part of the Single Unix Specification.

NOTES

The keyok() and define_key() functions are implementations of extensions made by the NCurses library to the Curses standard. Portable implementations should avoid the use of these functions.

HISTORY

The Curses package appeared in 4.0BSD. The is_keypad() and set_tabsize() functions are ncurses extension to the Curses library and was added in NetBSD 8.0.