form_field_validation(3X)                            form_field_validation(3X)

NAME
       form_field_validation - data type validation for fields

SYNOPSIS
       #include <form.h>
       int set_field_type(FIELD *field, FIELDTYPE *type, ...);
       FIELDTYPE *field_type(const FIELD *field);
       void *field_arg(const FIELD *field);

       FIELDTYPE *TYPE_ALNUM;
       FIELDTYPE *TYPE_ALPHA;
       FIELDTYPE *TYPE_ENUM;
       FIELDTYPE *TYPE_INTEGER;
       FIELDTYPE *TYPE_NUMERIC;
       FIELDTYPE *TYPE_REGEXP;
       FIELDTYPE *TYPE_IPV4;

DESCRIPTION
       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:

       TYPE_ALNUM
            Alphanumeric data.  Requires a third int argument, a minimum field
            width.

       TYPE_ALPHA
            Character data.  Requires a third int argument, a minimum field
            width.

       TYPE_ENUM
            Accept one of a specified set of strings.  Requires additional
            parameters:

            • 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.

                The library copies the string list, so you may use a list that
                lives in automatic variables on the stack.

       TYPE_INTEGER
            Integer data, parsable to an integer by atoi(3).  Requires
            additional parameters:

            • 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 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(3).

       TYPE_NUMERIC
            Numeric data (may have a decimal-point part).  This requires
            additional parameters:

            • a third int argument controlling the precision,

            • a fourth double argument constraining minimum value,

            • and a fifth double constraining maximum value.  If your system
                supports locales, the decimal point character 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(3).

       TYPE_REGEXP
            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.

            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.

       TYPE_IPV4
            An Internet Protocol Version 4 address.  This requires no
            additional argument.  The library checks 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.

            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.

RETURN VALUE
       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.

       E_SYSTEM_ERROR
            System error occurred (see errno(3)).

SEE ALSO
       curses(3X), form(3X), form_variables(3X).

NOTES
       The header file <form.h> automatically includes the header file
       <curses.h>.

PORTABILITY
       These routines emulate the System V forms library.  They were not
       supported on Version 7 or BSD versions.

AUTHORS
       Juergen Pfeifer.  Manual pages and adaptation for new curses by Eric S.
       Raymond.

                                                     form_field_validation(3X)