curs_getstr(3X) curs_getstr(3X)
getstr, getnstr, wgetstr, wgetnstr, mvgetstr, mvgetnstr, mvwgetstr,
mvwgetnstr - accept character strings from curses terminal keyboard
#include <curses.h>
int getstr(char *str);
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 *win, int y, int x, char *str, int n);
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.
The getnstr function reads from the stdscr default window. The other
functions, such as wgetnstr, read from the window given as a parameter.
getnstr 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 user's erase and kill characters are interpreted:
o The erase character (e.g., ^H) erases the character at the end of
the buffer, moving the cursor to the left.
If keypad mode is on for the window, KEY_LEFT and KEY_BACKSPACE are
both considered equivalent to the user's erase character.
o The kill character (e.g., ^U) erases the entire buffer, leaving the
cursor at the beginning of the buffer.
Characters input are echoed only if echo is currently on. In that
case, backspace is echoed as deletion of the previous character (typi-
cally a left motion).
All routines return the integer ERR upon failure and an OK (SVr4 speci-
fies only "an integer value other than ERR") upon successful comple-
tion.
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 data.
This implementation provides an extension as well. If a SIGWINCH in-
terrupts 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", with-
out 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:
o ncurses 6.1 and PDCurses do not count the NUL in the given limit,
while
o Solaris SVr4 and NetBSD curses count the NUL as part of the limit.
o Solaris xcurses provides both: its wide-character wget_nstr re-
serves a NUL, but its wgetnstr does not count the NUL consistently.
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:
o Solaris SVr4 curses and PDCurses limit the result to 255 bytes.
Other Unix systems than Solaris are likely to use the same limit.
o Solaris xcurses limits the result to LINE_MAX bytes.
o 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
SUSv2.
o ncurses (before 6.2) assumes no particular limit for the result
from wgetstr, and treats the n parameter of wgetnstr like SVr4
curses.
o 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 ter-
minating NUL.
Although getnstr is equivalent to a series of calls to getch, it also
makes changes to the curses modes to allow simple editing of the input
buffer:
o getnstr saves the current value of the nl, echo, raw and cbreak
modes, and sets nl, noecho, noraw, and cbreak.
getnstr handles the echoing of characters, rather than relying on
the caller to set an appropriate mode.
o It also obtains the erase and kill characters from erasechar and
killchar, respectively.
o On return, getnstr restores the modes to their previous values.
Other implementations differ in their treatment of special characters:
o While they may set the echo mode, other implementations do not mod-
ify the raw mode, They may take the cbreak mode set by the caller
into account when deciding whether to handle echoing within getnstr
or as a side-effect of the getch calls.
o The original ncurses (as pcurses in 1986) set noraw and cbreak when
accepting input for getnstr. That may have been done to make func-
tion- and cursor-keys work; it is not necessary with ncurses.
Since 1995, ncurses has provided signal handlers for INTR and QUIT
(e.g., ^C or ^\). With the noraw and cbreak settings, those may
catch a signal and stop the program, where other implementations
allow one to enter those characters in the buffer.
o Starting in 2021 (ncurses 6.3), getnstr sets raw, rather than noraw
and cbreak for better compatibility with SVr4-curses, e.g., allow-
ing one to enter a ^C into the buffer.
curses(3X), curs_getch(3X), curs_termattrs(3X), curs_variables(3X).
curs_getstr(3X)