+ The functions <STRONG>getnstr</STRONG>, <STRONG>mvgetnstr</STRONG>, and <STRONG>mvwgetnstr</STRONG> were present but not
+ documented in SVr4.
+
+ X/Open Curses, Issue 5 (2007) stated that these functions "read at most
+ <EM>n</EM> 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 <EM>n</EM>-1 bytes" to allow for the terminating NUL. As of 2018,
+ some implementations do, some do not count it:
+
+ <STRONG>o</STRONG> ncurses 6.1 and PDCurses do not count the NUL in the given limit,
+ while
+
+ <STRONG>o</STRONG> Solaris SVr4 and NetBSD curses count the NUL as part of the limit.
+
+ <STRONG>o</STRONG> Solaris xcurses provides both: its wide-character <STRONG>wget_nstr</STRONG> re-
+ serves a NUL, but its <STRONG>wgetnstr</STRONG> does not count the NUL consistently.
+
+ In SVr4 curses, a negative value of <EM>n</EM> tells <STRONG>wgetnstr</STRONG> to assume that the
+ caller's buffer is large enough to hold the result, i.e., to act like
+ <STRONG>wgetstr</STRONG>. X/Open Curses does not mention this (or anything related to
+ negative or zero values of <EM>n</EM>), however most implementations use the
+ feature, with different limits:
+
+ <STRONG>o</STRONG> Solaris SVr4 curses and PDCurses limit the result to 255 bytes.
+ Other Unix systems than Solaris are likely to use the same limit.
+
+ <STRONG>o</STRONG> Solaris xcurses limits the result to <STRONG>LINE_MAX</STRONG> bytes.
+
+ <STRONG>o</STRONG> NetBSD 7 assumes no particular limit for the result from <STRONG>wgetstr</STRONG>.
+ However, it limits the <STRONG>wgetnstr</STRONG> parameter <EM>n</EM> to ensure that it is
+ greater than zero.
+
+ A comment in NetBSD's source code states that this is specified in
+ SUSv2.
+
+ <STRONG>o</STRONG> ncurses (before 6.2) assumes no particular limit for the result
+ from <STRONG>wgetstr</STRONG>, and treats the <EM>n</EM> parameter of <STRONG>wgetnstr</STRONG> like SVr4
+ curses.
+
+ <STRONG>o</STRONG> ncurses 6.2 uses <STRONG>LINE_MAX</STRONG>, or a larger (system-dependent) value
+ which the <STRONG>sysconf</STRONG> function may provide. If neither <STRONG>LINE_MAX</STRONG> or
+ <STRONG>sysconf</STRONG> is available, ncurses uses the POSIX value for <STRONG>LINE_MAX</STRONG> (a
+ 2048 byte limit). In either case, it reserves a byte for the ter-
+ minating NUL.
+
+ Although <STRONG>getnstr</STRONG> is equivalent to a series of calls to <STRONG>getch</STRONG>, it also
+ makes changes to the curses modes to allow simple editing of the input
+ buffer:
+
+ <STRONG>o</STRONG> <STRONG>getnstr</STRONG> saves the current value of the <STRONG>nl</STRONG>, <STRONG>echo</STRONG>, <STRONG>raw</STRONG> and <STRONG>cbreak</STRONG>
+ modes, and sets <STRONG>nl</STRONG>, <STRONG>noecho</STRONG>, <STRONG>noraw</STRONG>, and <STRONG>cbreak</STRONG>.
+
+ <STRONG>getnstr</STRONG> handles the echoing of characters, rather than relying on
+ the caller to set an appropriate mode.
+
+ <STRONG>o</STRONG> It also obtains the <EM>erase</EM> and <EM>kill</EM> characters from <STRONG>erasechar</STRONG> and
+ <STRONG>killchar</STRONG>, respectively.
+
+ <STRONG>o</STRONG> On return, <STRONG>getnstr</STRONG> restores the modes to their previous values.
+
+ Other implementations differ in their treatment of special characters:
+
+ <STRONG>o</STRONG> While they may set the <EM>echo</EM> mode, other implementations do not mod-
+ ify the <EM>raw</EM> mode, They may take the <EM>cbreak</EM> mode set by the caller
+ into account when deciding whether to handle echoing within <STRONG>getnstr</STRONG>
+ or as a side-effect of the <STRONG>getch</STRONG> calls.
+
+ <STRONG>o</STRONG> The original ncurses (as pcurses in 1986) set <STRONG>noraw</STRONG> and <STRONG>cbreak</STRONG> when
+ accepting input for <STRONG>getnstr</STRONG>. 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., <STRONG>^C</STRONG> or <STRONG>^\</STRONG>). With the <STRONG>noraw</STRONG> and <STRONG>cbreak</STRONG> settings, those may
+ catch a signal and stop the program, where other implementations
+ allow one to enter those characters in the buffer.
+
+ <STRONG>o</STRONG> Starting in 2021 (ncurses 6.3), <STRONG>getnstr</STRONG> sets <STRONG>raw</STRONG>, rather than <STRONG>noraw</STRONG>
+ and <STRONG>cbreak</STRONG> for better compatibility with SVr4-curses, e.g., allow-
+ ing one to enter a <STRONG>^C</STRONG> into the buffer.
+
+
+</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
+ <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_getch.3x.html">curs_getch(3x)</A></STRONG>, <STRONG><A HREF="curs_termattrs.3x.html">curs_termattrs(3x)</A></STRONG>, <STRONG><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>.
projects / ncurses.git / blobdiff