form_field_validation - data type validation for fields
int set_field_type(FIELD *field, FIELDTYPE *type, ...);
FIELDTYPE *field_type(const FIELD *field);
void *field_arg(const FIELD *field);
The function set_field_type declares a data type for a given form field. This is the type checked by validation functions. The predefined
types are as follows:
Alphanumeric data. Requires a third int argument, a minimum field width.
Character data. Requires a third int argument, a minimum field width.
Accept one of a specified set of strings. Requires a third (char **) argument pointing to a string list; a fourth int flag argument
to enable case-sensitivity; and a fifth int flag argument specifying whether a partial match must be a unique one (if this flag is
off, a prefix matches the first of any set of more than one list elements with that prefix). Please notice that the string list is not
copied, only a reference to it is stored in the field. So you should avoid using a list that lives in automatic variables on the
Integer data, parsable to an integer by atoi(3). Requires a third int argument controlling the precision, a fourth long argument con-
straining minimum value, and a fifth long constraining maximum value. If the maximum value is less than or equal to the minimum
value, the range is simply ignored. On return the field buffer is formatted according to the printf format specification ".*ld", where
the '*' is replaced by the precision argument. For details of the precision handling see printf's man-page.
Numeric data (may have a decimal-point part). Requires a third int argument controlling the precision, a fourth double argument con-
straining minimum value, and a fifth double constraining maximum value. If your system supports locales, the decimal point character
to be used must be the one specified by your locale. If the maximum value is less than or equal to the minimum value, the range is
simply ignored. On return the field buffer is formatted according to the printf format specification ".*f", where the '*' is replaced
by the precision argument. For details of the precision handling see printf's man-page.
Regular expression data. Requires a regular expression (char *) third argument; the data is valid if the regular expression matches
it. Regular expressions are in the format of regcomp and regexec. Please notice that 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.
An Internet Protocol Version 4 address. This requires no additional argument. It is checked whether or not the buffer has the form
a.b.c.d, where a,b,c and d are numbers between 0 and 255. Trailing blanks in the buffer are ignored. The address itself is not vali-
dated. Please note that this is an ncurses extension. This field type may not be available in other curses implementations.
It is possible to set up new programmer-defined field types. See the form_fieldtype(3X) manual page.
The functions field_type and field_arg return NULL on error. The function set_field_type returns one of the following:
E_OK The routine succeeded.
System error occurred (see errno).
The header file <form.h> automatically includes the header file <curses.h>.
These routines emulate the System V forms library. They were not supported on Version 7 or BSD versions.
Juergen Pfeifer. Manual pages and adaptation for new curses by Eric S. Raymond.