curs_get_wch(3X)

NAME
get_wch, wget_wch, mvget_wch, mvwget_wch, unget_wch - get (or push back) a wide character from curses terminal keyboard

SYNOPSIS
#include <curses.h>

int get_wch(wint_t *wch);
int wget_wch(WINDOW *win, wint_t *wch);
int mvget_wch(int y, int x, wint_t *wch);
int mvwget_wch(WINDOW *win, int y, int x, wint_t *wch);

int unget_wch(const wchar_t wch);

DESCRIPTION

  wget_wch
The get_wch, wget_wch, mvget_wch, and mvwget_wch functions read a character from the terminal associated with the current or specified window. In no-delay mode, if no input is waiting, the value ERR is returned. In delay mode, the program waits until the system passes text through to the program. Depending on the setting of cbreak, this is after one character (cbreak mode), or after the first newline (nocbreak mode). In half-delay mode, the program waits until the user types a character or the specified timeout interval has elapsed.

Unless noecho has been set, these routines echo the character into the designated window.

If the window is not a pad and has been moved or modified since the last call to wrefresh, wrefresh will be called before another character is read.

If keypad is enabled, these functions respond to the pressing of a function key by setting the object pointed to by wch to the keycode assigned to the function key, and returning KEY_CODE_YES. If a character (such as escape) that could be the beginning of a function key is received, curses sets a timer. If the remainder of the sequence does arrive within the designated time, curses passes through the character; otherwise, curses returns the function key value. For this reason, many terminals experience a delay between the time a user presses the escape key and the time the escape is returned to the program.

The keycodes returned by these functions are the same as those returned by wgetch: The predefined function keys are listed in <curses.h> as macros with values outside the range of 8-bit characters. Their names begin with KEY_. Other (user-defined) function keys which may be defined using define_key(3X) have no names, but also are expected to have values outside the range of 8-bit characters.

  unget_wch
The unget_wch function pushes the wide character wch back onto the head of the input queue, so the wide character is returned by the next call to get_wch. The pushback of one character is guaranteed. If the program calls unget_wch too many times without an intervening call to get_wch, the operation may fail.

Unlike ungetch and wgetch, unget_wch cannot distinguish special characters returned by wget_wch from ordinary characters. An application can push special keys which it may read via wget_wch by checking for the KEY_CODE_YES result, and using ungetch for those special keys.

RETURN VALUE
When get_wch, wget_wch, mvget_wch, and mvwget_wch functions successfully report the pressing of a function key, they return KEY_CODE_YES. When they successfully report a wide character, they return OK. Otherwise, they return ERR.

Upon successful completion, unget_wch returns OK. Otherwise, the function returns ERR.

Functions with a “mv” prefix first perform a cursor movement using wmove, and return an error if the position is outside the window, or if the window pointer is null.

NOTES
Applications should not define the escape key by itself as a single-character function.

When using get_wch, wget_wch, mvget_wch, or mvwget_wch, applications should not use nocbreak mode and echo mode at the same time. Depending on the state of the tty driver when each character is typed, the program may produce undesirable results.

All of these functions except wget_wch and unget_wch may be implemented as macros.

PORTABILITY
These functions are described in the XSI Curses standard, Issue 4.

SEE ALSO
curses(3X), curs_getch(3X), curs_inopts(3X), curs_ins_wch(3X), curs_move(3X), curs_refresh(3X)