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 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 copied. 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 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's man-page.

       TYPE_NUMERIC
            Numeric  data  (may  have  a  decimal-point  part).  Requires  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 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.

       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.
            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.

       TYPE_IPV4
            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 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 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).

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)