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 types
are as follows:
Alphanumeric data. Requires a third int argument, a minimum field
Character data. Requires a third int argument, a minimum field
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 specify‐
ing 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 to use a list that lives in automatic variables on
Integer data, parsable to an integer by atoi(3). Requires a third
int argument controlling the precision, a fourth long argument
constraining minimum value, and a fifth long constraining maximum
value. If the maximum value is less or equal the minimum value,
the range is simply ignored. On return the field buffer is format‐
ted 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 locale's, the decimal point charac‐
ter to be used must be the one specified by your locale. If the
maximum value is less or equal 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(3X)
and regexec(3X). 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 addi‐
tional 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 validated. 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 func‐
tion set_field_type returns one of the following:
E_OK The routine succeeded.
System error occurred (see errno).
SEE ALSOcurses(3X), form(3X).
The header file <form.h> automatically includes the header file
These routines emulate the System V forms library. They were not sup‐
ported on Version 7 or BSD versions.
Juergen Pfeifer. Manual pages and adaptation for new curses by Eric S.