+.PP
+X/Open Curses, Issue 5 (2007) stated that these functions
+\*(``read at most \fIn\fP 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 \fIn\fP\-1 bytes\*(''
+to allow for the terminating NUL.
+As of 2018, some implementations do, some do not count it:
+.bP
+ncurses 6.1 and PDCurses do not count the NUL in the given limit, while
+.bP
+Solaris SVr4 and NetBSD curses count the NUL as part of the limit.
+.bP
+Solaris xcurses provides both:
+its wide-character \fBwget_nstr\fP reserves a NUL,
+but its \fBwgetnstr\fP does not count the NUL consistently.
+.PP
+In SVr4 curses,
+a negative value of \fIn\fP tells \fBwgetnstr\fP to assume that the
+caller's buffer is large enough to hold the result,
+i.e., to act like \fBwgetstr\fP.
+X/Open Curses does not mention this
+(or anything related to negative or zero values of \fIn\fP),
+however most implementations
+use the feature, with different limits:
+.bP
+Solaris SVr4 curses and PDCurses limit the result to 255 bytes.
+Other Unix systems than Solaris are likely to use the same limit.
+.bP
+Solaris xcurses limits the result to \fBLINE_MAX\fP bytes.
+.bP
+NetBSD 7 assumes no particular limit for the result from \fBwgetstr\fP.
+However, it limits the \fBwgetnstr\fP parameter \fIn\fP to ensure
+that it is greater than zero.
+.IP
+A comment in NetBSD's source code states that this is specified in SUSv2.
+.bP
+ncurses (before 6.2) assumes no particular limit for the result
+from \fBwgetstr\fP, and treats the \fIn\fP parameter of \fBwgetnstr\fP
+like SVr4 curses.
+.bP
+ncurses 6.2 uses \fBLINE_MAX\fP,
+or a larger (system-dependent) value
+which the \fBsysconf\fP function may provide.
+If neither \fBLINE_MAX\fP or \fBsysconf\fP is available,
+ncurses uses the POSIX value for \fBLINE_MAX\fP (a 2048 byte limit).
+In either case, it reserves a byte for the terminating NUL.
+.PP
+Although \fBgetnstr\fP is equivalent to a series of calls to \fBgetch\fP,
+it also makes changes to the curses modes to allow simple editing of
+the input buffer:
+.bP
+\fBgetnstr\fP saves the current value of the \fBnl\fP, \fBecho\fP,
+\fBraw\fP and \fBcbreak\fP modes, and sets
+\fBnl\fP,
+\fBnoecho\fP,
+\fBnoraw\fP, and
+\fBcbreak\fP.
+.IP
+\fBgetnstr\fP handles the echoing of characters,
+rather than relying on the caller to set an appropriate mode.
+.bP
+It also obtains the \fIerase\fP and \fIkill\fP characters
+from \fBerasechar\fP and \fBkillchar\fP, respectively.
+.bP
+On return, \fBgetnstr\fP restores the modes to their previous values.
+.PP
+Other implementations differ in their treatment of special characters:
+.bP
+While they may set the \fIecho\fP mode,
+other implementations do not modify the \fIraw\fP mode,
+They may take the \fIcbreak\fP
+mode set by the caller into account when deciding whether to handle
+echoing within \fBgetnstr\fP or as a side-effect of the \fBgetch\fP calls.
+.bP
+The original ncurses (as pcurses in 1986) set \fBnoraw\fP and \fBcbreak\fP
+when accepting input for \fBgetnstr\fP.
+That may have been done to make function- and cursor-keys work;
+it is not necessary with ncurses.
+.IP
+Since 1995, ncurses has provided signal handlers for INTR and QUIT
+(e.g., \fB^C\fP or \fB^\\\fP).
+With the \fBnoraw\fP and \fBcbreak\fP settings,
+those may catch a signal and stop the program,
+where other implementations allow one to enter those characters in the buffer.
+.bP
+Starting in 2021 (ncurses 6.3), \fBgetnstr\fP sets \fBraw\fP,
+rather than \fBnoraw\fP and \fBcbreak\fP for better compatibility with
+SVr4-curses, e.g., allowing one to enter a \fB^C\fP into the buffer.
projects / ncurses.git / blobdiff