- 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 function wgetnstr is equivalent to a series of calls to wgetch(3x),
+ until a newline or carriage return terminates the series:
+
+ o The terminating character is not included in the returned string.
+
+ o In all instances, the end of the string is terminated by a NUL.
+
+ o The function stores the result in the area pointed to by the str
+ parameter.
+
+ o The function 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.
- 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.
+ If keypad mode is on for the window, KEY_LEFT and KEY_BACKSPACE are
+ both considered equivalent to the user's erase character.
- 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.
+ 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).
+ case, backspace is echoed as deletion of the previous character
+ (typically a left motion).
+
+ The getnstr, mvgetnstr, mvwgetnstr, and wgetnstr functions are
+ identical to the getstr, mvgetstr, mvwgetstr, and wgetstr functions,
+ respectively, except that the *n* versions read at most n characters,
+ letting the application prevent overflow of the input buffer.
- 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.
+ All of these functions return the integer OK upon successful
+ completion. (SVr4 specifies only "an integer value other than ERR") If
+ unsuccessful, they return ERR.
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.
+ In this implementation, these functions return an error
+
+ o if the window pointer is null,
+
+ o if its timeout expires without having any data, or
- This implementation provides an extension as well. If a SIGWINCH in-
- terrupts the function, it will return KEY_RESIZE rather than OK or ERR.
+ o if the associated call to wgetch failed.
- 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.
+ This implementation provides an extension as well. If a SIGWINCH
+ interrupts the function, it will return KEY_RESIZE rather than OK or
+ ERR.
+
+ Functions prefixed with "mv" first perform cursor movement and fail if
+ the position (y, x) is outside the window boundaries.
- Note that getstr, mvgetstr, and mvwgetstr may be macros.
+ Any of these functions other than wgetnstr may be macros.
+
+ Using getstr, mvgetstr, mvwgetstr, or wgetstr to read a line that
+ overflows the array pointed to by str causes undefined results. The
+ use of getnstr, mvgetnstr, mvwgetnstr, or wgetnstr, respectively, is
+ recommended.
- 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.
+ These functions are described in The Single Unix Specification, Version
+ 2. No error conditions are defined.
+
+ 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).
+ 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
+ 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 count it, some do not:
+
+ oncurses 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
+ reserves 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.
+
+ oncurses (before 6.2) assumes no particular limit for the result
+ from wgetstr, and treats the n parameter of wgetnstr like SVr4
+ curses.
+
+ oncurses 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.
+
+ 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
+ modify 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
+ function- 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.,
+ allowing one to enter a ^C into the buffer.
+