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.
+ 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:
- wgetnstr reads at most n characters, thus preventing a possible over-
- flow of the input buffer. Any attempt to enter more characters (other
- than the terminating newline or carriage return) causes a beep. Func-
- tion keys also cause a beep and are ignored. The getnstr function
- reads from the stdscr default window.
+ o The erase character (e.g., ^H) erases the character at the end of
+ the buffer, moving the cursor to the left.
- 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.
+ If keypad mode is on for the window, KEY_LEFT and KEY_BACKSPACE are
+ both considered equivalent to the user's erase character.
- Characters input are echoed only if echo is currently on. In that
- case, backspace is echoed as deletion of the previous character (typi-
+ 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-
+ 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
+ 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-
+ 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
+ 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.
@@ -107,24 +121,101 @@
- 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
+ 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
+ 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
+ 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:
+
+ ogetnstr 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.
+