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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | SEE ALSO | NOTES | PORTABILITY | AUTHORS | COLOPHON |
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form_fieldtype(3X) form_fieldtype(3X)
form_fieldtype - define validation-field types
#include <form.h>
FIELDTYPE *new_fieldtype(
bool (* const field_check)(FIELD *, const void *),
bool (* const char_check)(int, const void *));
int free_fieldtype(FIELDTYPE *fieldtype);
int set_fieldtype_arg(
FIELDTYPE *fieldtype,
void *(* const make_arg)(va_list *),
void *(* const copy_arg)(const void *),
void (* const free_arg)(void *));
int set_fieldtype_choice(
FIELDTYPE *fieldtype,
bool (* const next_choice)(FIELD *, const void *),
bool (* const prev_choice)(FIELD *, const void *));
FIELDTYPE *link_fieldtype(FIELDTYPE *type1,
FIELDTYPE *type2);
new_fieldtype
The function new_fieldtype creates a new field type usable for
data validation. Its parameters are function pointers:
field_check
This function checks the validity of an entered data string
whenever the user attempts to leave a field. It has two
arguments:
• The (FIELD *) argument is passed in so the validation
predicate can see the field's buffer, sizes and other
attributes.
• The second argument is an argument-block structure, about
which more below.
char_check
This function validates input characters as they are entered.
The form library passes it the character to be checked and a
pointer to an argument-block structure.
free_fieldtype
The free_fieldtype function frees the space allocated for a given
validation type by new_fieldtype.
set_fieldtype_arg
The function set_fieldtype_arg associates three storage-management
functions with a field type:
make_arg
This function is automatically applied to the list of
arguments you give set_field_type when attaching validation
to a field. It stores the arguments in an allocated
argument-block object which is used when validating input.
copy_arg
This function may be used by applications to copy argument-
blocks.
free_arg
Frees an argument-block structure.
You must supply the make_arg function. The other two are
optional: you may supply NULL for them. In this case, the form
library assumes that make_arg does not allocate memory but simply
loads the argument into a single scalar value.
set_fieldtype_choice
The form driver requests REQ_NEXT_CHOICE and REQ_PREV_CHOICE
assume that the possible values of a field form an ordered set,
and provide the forms user with a way to move through the set.
The set_fieldtype_choice function allows forms programmers to
define successor and predecessor functions for the field type.
These functions take the field pointer and an argument-block
structure as arguments.
link_fieldtype
The function link_fieldtype creates a new field type from the two
given types. They are connected by an logical 'OR'.
The pointer-valued routines return NULL on error. They set errno
according to their success:
E_OK The routine succeeded.
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
E_SYSTEM_ERROR
System error occurred, e.g., malloc failure.
The integer-valued routines return one of the following codes on
error:
E_OK The routine succeeded.
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
E_CONNECTED
The field is already connected to a form.
E_CURRENT
The field is the current field.
E_SYSTEM_ERROR
System error occurred (see errno(3)).
curses(3X), form(3X), form_field_validation(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.
This page is part of the ncurses (new curses) project.
Information about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to
[email protected]. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨https://github.com/mirror/ncurses.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2023-03-12.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
form_fieldtype(3X)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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