# form_field_validation 3x

    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 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 preci-
                sion, 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  preci-
                sion,  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 expres-
                sion (char *) third argument; the data  is  valid  if
                the  regular  expression matches it.  Regular expres-
                sions 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]*$"
                always means that you have to fill  all  eight  posi-
                tions with digits. If you want to allow fewer digits,
                you may use for example "^[0-9]* *$"  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 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.

## RETURN VALUE

           The  functions  field_type  and  field_arg  return NULL on
           error. The function set_field_type returns one of the fol-
           lowing:

           E_OK The routine succeeded.

           E_SYSTEM_ERROR
                System error occurred (see errno).

## 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)