form_field_validation(3x) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | SEE ALSO | NOTES | PORTABILITY | AUTHORS | COLOPHON

form_field_validation(3X)                      form_field_validation(3X)

NAME         top

       form_field_validation - data type validation for fields

SYNOPSIS         top

       #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;

DESCRIPTION         top

       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.

   field_arg
       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.

   field_type
       Returns a pointer to the field type associated with the form
       field, i.e., by calling set_field_type.

   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.

   Predefined types
       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:

       TYPE_ALNUM
            Alphanumeric data.  Required parameter:

            •   a third int argument, a minimum field width.

       TYPE_ALPHA
            Character data.  Required parameter:

            •   a third int argument, a minimum field width.

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

            •   a third (char **) argument pointing to a string list;

            •   a fourth int flag argument to enable case-sensitivity;

            •   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).  Required
            parameters:

            •   a third int argument controlling the precision,

            •   a fourth long argument constraining minimum value,

            •   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).  Required
            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.  Required parameter:

            •   a third argument, a regular expression (char *) string.
                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.  Required parameter:

            •   none

            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.

RETURN VALUE         top

       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         top

       curses(3X), form(3X), form_fieldtype(3X), form_variables(3X).

NOTES         top

       The header file <form.h> automatically includes the header file
       <curses.h>.

PORTABILITY         top

       These routines emulate the System V forms library.  They were not
       supported on Version 7 or BSD versions.

AUTHORS         top

       Juergen Pfeifer.  Manual pages and adaptation for new curses by
       Eric S. Raymond.

COLOPHON         top

       This page is part of the ncurses (new curses) project.
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       ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩.  If you have
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       ⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2021-08-27.  (At
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                                               form_field_validation(3X)