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 fieldtype(3FORM)
       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

       ncurses(3NCURSES), form(3FORM), form_variables(3FORM).

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.

                                                                          field_validation(3FORM)