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- * @Id: curs_getstr.3x,v 1.23 2017/11/21 00:45:48 tom Exp @
+ * @Id: curs_getstr.3x,v 1.29 2020/02/02 23:34:34 tom Exp @
+ * X/Open says also until EOf
+ * X/Open says then an EOS is added to the result
+ * X/Open doesn't mention n<0
-->
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The function <STRONG>getstr</STRONG> is equivalent to a series of calls to <STRONG>getch</STRONG>, 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 <EM>str</EM>.
+ the area pointed to by the character pointer <EM>str</EM>, followed by a NUL.
<STRONG>wgetnstr</STRONG> reads at most <EM>n</EM> characters, thus preventing a possible over-
flow of the input buffer. Any attempt to enter more characters (other
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.
+
</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_variables.3x.html">curs_variables(3x)</A></STRONG>.
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