+ <STRONG>o</STRONG> a third argument, a regular expression <STRONG>(char</STRONG> <STRONG>*)</STRONG> string. The data
+ is valid if the regular expression matches it.
+
+ Regular expressions are in the format of <STRONG>regcomp</STRONG> and <STRONG>regexec</STRONG>.
+
+ The regular expression must match the whole field. If you have for
+ example, an eight character wide field, a regular expression "^[0-9]*$"
+ always means that you have to fill all eight positions with digits. If
+ you want to allow fewer digits, you may use for example "^[0-9]* *$"
+ which is good for trailing spaces (up to an empty field), or "^ *[0-9]*
+ *$" which is good for leading and trailing spaces around the digits.
+
+
+</PRE><H3><a name="h3-TYPE_IPV4">TYPE_IPV4</a></H3><PRE>
+ An Internet Protocol Version 4 address. Required parameter:
+
+ <STRONG>o</STRONG> none
+
+ The form library checks whether or not the buffer has the form <EM>a.b.c.d</EM>,
+ where <EM>a</EM>, <EM>b</EM>, <EM>c</EM>, and <EM>d</EM> are numbers in the range 0 to 255. Trailing
+ blanks in the buffer are ignored. The address itself is not validated.
+
+ This is an ncurses extension; this field type may not be available in
+ other curses implementations.