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$Id: form_field_validation.3x,v 1.33 2020/12/12 19:57:55 tom Exp $
.. form_field_validation - data type validation for fields #include <form.h> void *field_arg(const FIELD *field);

FIELDTYPE *field_type(const FIELD *field);

int set_field_type(FIELD *field, FIELDTYPE *type, ...); /* predefined field types */

FIELDTYPE *TYPE_ALNUM;

FIELDTYPE *TYPE_ALPHA;

FIELDTYPE *TYPE_ENUM;

FIELDTYPE *TYPE_INTEGER;

FIELDTYPE *TYPE_NUMERIC;

FIELDTYPE *TYPE_REGEXP;

FIELDTYPE *TYPE_IPV4;

By default, no validation is done on form fields. You can associate a form with with a field type, making the form library validate input. Returns a pointer to the field's argument block. The argument block is an opaque structure containing a copy of the arguments provided in a set_field_type call. Returns a pointer to the field type associated with the form field, i.e., by calling set_field_type. The function set_field_type associates a field type with a given form field. This is the type checked by validation functions. Most field types are configurable, via arguments which the caller provides when calling set_field_type.

Several field types are predefined by the form library.

It is possible to set up new programmer-defined field types. Field types are implemented via the FIELDTYPE data structure, which contains several pointers to functions.

See the form_fieldtype(3X) manual page, which describes functions which can be used to construct a field-type dynamically.

The predefined types are as follows:

5 TYPE_ALNUM Alphanumeric data. Required parameter:

5 TYPE_ALPHA Character data. Required parameter:

5 TYPE_ENUM Accept one of a specified set of strings. Required parameters:

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

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

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).

5 TYPE_NUMERIC Numeric data (may have a decimal-point part). Required parameters:

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).

5 TYPE_REGEXP Regular expression data. Required parameter:

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.

5 TYPE_IPV4 An Internet Protocol Version 4 address. Required parameter:

The form library checks whether or not the buffer has the form a.b.c.d, where a, b, c, and d are numbers in the range 0 to 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. The functions field_type and field_arg return NULL on error. The function set_field_type returns one of the following:

5 E_OK The routine succeeded.

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

curses(3X), form(3X), form_fieldtype(3X), form_variables(3X). The header file <form.h> automatically includes the header file <curses.h>. These routines emulate the System V forms library. They were not supported on Version 7 or BSD versions. Juergen Pfeifer. Manual pages and adaptation for new curses by Eric S. Raymond.