1curs_getstr(3X) curs_getstr(3X)
2
6 getstr, getnstr, wgetstr, wgetnstr, mvgetstr, mvgetnstr, mvwgetstr,
7 mvwgetnstr - accept character strings from curses terminal keyboard
8
10 #include <curses.h>
11 int getstr(char *str);
13 int getnstr(char *str, int n);
14 int wgetstr(WINDOW *win, char *str);
15 int wgetnstr(WINDOW *win, char *str, int n);
16 int mvgetstr(int y, int x, char *str);
18 int mvwgetstr(WINDOW *win, int y, int x, char *str);
19 int mvgetnstr(int y, int x, char *str, int n);
20 int mvwgetnstr(WINDOW *win, int y, int x, char *str, int n);
21
23 The function getstr is equivalent to a series of calls to getch, until
24 a newline or carriage return is received (the terminating character is
25 not included in the returned string). The resulting value is placed in
26 the area pointed to by the character pointer str, followed by a NUL.
27 The getnstr function reads from the stdscr default window. The other
29 functions, such as wgetnstr, read from the window given as a parameter.
30 getnstr reads at most n characters, thus preventing a possible overflow
32 of the input buffer. Any attempt to enter more characters (other than
33 the terminating newline or carriage return) causes a beep. Function
34 keys also cause a beep and are ignored.
35 The user's erase and kill characters are interpreted:
37 • The erase character (e.g., ^H) erases the character at the end of
39 the buffer, moving the cursor to the left.
40 If keypad mode is on for the window, KEY_LEFT and KEY_BACKSPACE are
42 both considered equivalent to the user's erase character.
43 • The kill character (e.g., ^U) erases the entire buffer, leaving the
45 cursor at the beginning of the buffer.
46 Characters input are echoed only if echo is currently on. In that
48 case, backspace is echoed as deletion of the previous character (typi‐
49 cally a left motion).
50
52 All routines return the integer ERR upon failure and an OK (SVr4 speci‐
53 fies only “an integer value other than ERR”) upon successful comple‐
54 tion.
55 X/Open defines no error conditions.
57 In this implementation, these functions return an error if the window
59 pointer is null, or if its timeout expires without having any data.
60 This implementation provides an extension as well. If a SIGWINCH in‐
62 terrupts the function, it will return KEY_RESIZE rather than OK or ERR.
63 Functions with a “mv” prefix first perform a cursor movement using
65 wmove, and return an error if the position is outside the window, or if
66 the window pointer is null.
67
69 Note that getstr, mvgetstr, and mvwgetstr may be macros.
70
72 These functions are described in the XSI Curses standard, Issue 4.
73 They read single-byte characters only. The standard does not define
74 any error conditions. This implementation returns ERR if the window
75 pointer is null, or if the lower-level wgetch(3X) call returns an ERR.
76 SVr3 and early SVr4 curses implementations did not reject function
78 keys; the SVr4.0 documentation claimed that “special keys” (such as
79 function keys, “home” key, “clear” key, etc.) are “interpreted”, with‐
80 out giving details. It lied. In fact, the “character” value appended
81 to the string by those implementations was predictable but not useful
82 (being, in fact, the low-order eight bits of the key's KEY_ value).
83 The functions getnstr, mvgetnstr, and mvwgetnstr were present but not
85 documented in SVr4.
86 X/Open Curses, Issue 5 (2007) stated that these functions “read at most
88 n bytes” but did not state whether the terminating NUL is counted in
89 that limit. X/Open Curses, Issue 7 (2009) changed that to say they
90 “read at most n-1 bytes” to allow for the terminating NUL. As of 2018,
91 some implementations do, some do not count it:
92 • ncurses 6.1 and PDCurses do not count the NUL in the given limit,
94 while
95 • Solaris SVr4 and NetBSD curses count the NUL as part of the limit.
97 • Solaris xcurses provides both: its wide-character wget_nstr re‐
99 serves a NUL, but its wgetnstr does not count the NUL consistently.
100 In SVr4 curses, a negative value of n tells wgetnstr to assume that the
102 caller's buffer is large enough to hold the result, i.e., to act like
103 wgetstr. X/Open Curses does not mention this (or anything related to
104 negative or zero values of n), however most implementations use the
105 feature, with different limits:
106 • Solaris SVr4 curses and PDCurses limit the result to 255 bytes.
108 Other Unix systems than Solaris are likely to use the same limit.
109 • Solaris xcurses limits the result to LINE_MAX bytes.
111 • NetBSD 7 assumes no particular limit for the result from wgetstr.
113 However, it limits the wgetnstr parameter n to ensure that it is
114 greater than zero.
115 A comment in NetBSD's source code states that this is specified in
117 SUSv2.
118 • ncurses (before 6.2) assumes no particular limit for the result
120 from wgetstr, and treats the n parameter of wgetnstr like SVr4
121 curses.
122 • ncurses 6.2 uses LINE_MAX, or a larger (system-dependent) value
124 which the sysconf function may provide. If neither LINE_MAX or
125 sysconf is available, ncurses uses the POSIX value for LINE_MAX (a
126 2048 byte limit). In either case, it reserves a byte for the ter‐
127 minating NUL.
128 Although getnstr is equivalent to a series of calls to getch, it also
130 makes changes to the curses modes to allow simple editing of the input
131 buffer:
132 • getnstr saves the current value of the nl, echo, raw and cbreak
134 modes, and sets nl, noecho, noraw, and cbreak.
135 getnstr handles the echoing of characters, rather than relying on
137 the caller to set an appropriate mode.
138 • It also obtains the erase and kill characters from erasechar and
140 killchar, respectively.
141 • On return, getnstr restores the modes to their previous values.
143 Other implementations differ in their treatment of special characters:
145 • While they may set the echo mode, other implementations do not mod‐
147 ify the raw mode, They may take the cbreak mode set by the caller
148 into account when deciding whether to handle echoing within getnstr
149 or as a side-effect of the getch calls.
150 • The original ncurses (as pcurses in 1986) set noraw and cbreak when
152 accepting input for getnstr. That may have been done to make func‐
153 tion- and cursor-keys work; it is not necessary with ncurses.
154 Since 1995, ncurses has provided signal handlers for INTR and QUIT
156 (e.g., ^C or ^\). With the noraw and cbreak settings, those may
157 catch a signal and stop the program, where other implementations
158 allow one to enter those characters in the buffer.
159 • Starting in 2021 (ncurses 6.3), getnstr sets raw, rather than noraw
161 and cbreak for better compatibility with SVr4-curses, e.g., allow‐
162 ing one to enter a ^C into the buffer.
163
165 curses(3X), curs_getch(3X), curs_termattrs(3X), curs_variables(3X).
166 curs_getstr(3X)