getstr, getnstr, wgetstr, wgetnstr, mvgetstr,
mvgetnstr, mvwgetstr, mvwgetnstr - accept character
strings from curses terminal keyboard
int getstr(char *str);
The function getstr is equivalent to a series of calls to getch,
until a newline or carriage return is received (the terminating character is
not included in the returned string). The resulting value is placed in the
area pointed to by the character pointer str, followed by a NUL.
int getnstr(char *str, int n);
int wgetstr(WINDOW *win, char *str);
int wgetnstr(WINDOW *win, char *str, int n);
int mvgetstr(int y, int x, char *str);
int mvwgetstr(WINDOW *win, int y, int x, char *str);
int mvgetnstr(int y, int x, char *str, int n);
int mvwgetnstr(WINDOW *, int y, int x, char *str, int n);
wgetnstr reads at most n characters, thus preventing
a possible overflow of the input buffer. Any attempt to enter more
characters (other than the terminating newline or carriage return) causes a
beep. Function keys also cause a beep and are ignored. The getnstr
function reads from the stdscr default window.
The user's erase and kill characters are interpreted. If keypad
mode is on for the window, KEY_LEFT and KEY_BACKSPACE are both
considered equivalent to the user's kill character.
Characters input are echoed only if echo is currently on.
In that case, backspace is echoed as deletion of the previous character
(typically a left motion).
All routines return the integer ERR upon failure and an OK (SVr4
specifies only “an integer value other than ERR”) upon
X/Open defines no error conditions.
In this implementation, these functions return an error if the
window pointer is null, or if its timeout expires without having any
This implementation provides an extension as well. If a
SIGWINCH interrupts the function, it will return KEY_RESIZE
rather than OK or 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.
Note that getstr, mvgetstr, and mvwgetstr may be macros.
These functions are described in the XSI Curses standard, Issue 4. They read
single-byte characters only. The standard does not define any error
conditions. This implementation returns ERR if the window pointer is
null, or if the lower-level wgetch(3X) call returns an ERR.
SVr3 and early SVr4 curses implementations did not reject function
keys; the SVr4.0 documentation claimed that “special keys”
(such as function keys, “home” key, “clear” key,
etc.) are “interpreted”, without giving details. It
lied. In fact, the “character” value appended to the string by
those implementations was predictable but not useful (being, in fact, the
low-order eight bits of the key's KEY_ value).
The functions getnstr, mvgetnstr, and
mvwgetnstr were present but not documented in SVr4.
X/Open Curses, Issue 5 (2007) stated that these functions
“read at most n bytes” but did not state whether the
terminating NUL is counted in that limit. X/Open Curses, Issue 7 (2009)
changed that to say they “read at most n-1 bytes” to
allow for the terminating NUL. As of 2018, some implementations do, some do
not count it:
- ncurses 6.1 and PDCurses do not count the NUL in the given limit,
- Solaris SVr4 and NetBSD curses count the NUL as part of the limit.
- Solaris xcurses provides both: its wide-character wget_nstr
reserves a NUL, but its wgetnstr does not count the NUL
In SVr4 curses, a negative value of n tells wgetnstr
to assume that the caller's buffer is large enough to hold the result, i.e.,
to act like wgetstr. X/Open Curses does not mention this (or anything
related to negative or zero values of n), however most
implementations use the feature, with different limits:
- Solaris SVr4 curses and PDCurses limit the result to 255 bytes. Other Unix
systems than Solaris are likely to use the same limit.
- Solaris xcurses limits the result to LINE_MAX bytes.
- NetBSD 7 assumes no particular limit for the result from wgetstr.
However, it limits the wgetnstr parameter n to ensure that
it is greater than zero.
- A comment in NetBSD's source code states that this is specified in
curses(3X), curs_getch(3X), curs_variables(3X).
- ncurses (before 6.2) assumes no particular limit for the result from
wgetstr, and treats the n parameter of wgetnstr like
- ncurses 6.2 uses LINE_MAX, or a larger (system-dependent) value
which the sysconf function may provide. If neither LINE_MAX
or sysconf is available, ncurses uses the POSIX value for
LINE_MAX (a 2048 byte limit). In either case, it reserves a byte
for the terminating NUL.