# phpman > perldoc > Dpkg::Control::FieldsCore

## NAME
    [Dpkg::Control::FieldsCore](https://www.chedong.com/phpMan.php/perldoc/Dpkg%3A%3AControl%3A%3AFieldsCore/markdown) - manage (list of official) control fields

## DESCRIPTION
    The modules contains a list of fieldnames with associated meta-data explaining in which type of
    control information they are allowed. The types are the CTRL_* constants exported by
    [Dpkg::Control](https://www.chedong.com/phpMan.php/perldoc/Dpkg%3A%3AControl/markdown).

## FUNCTIONS
    $f = field_capitalize($field_name)
        Returns the field name properly capitalized. All characters are lowercase, except the first
        of each word (words are separated by a hyphen in field names).

### field_is_official
        Returns true if the field is official and known.

### field_is_allowed_in
        Returns true (1) if the field $fname is allowed in all the types listed in the list. Note
        that you can use type sets instead of individual types (ex: CTRL_FILE_CHANGES |
        CTRL_CHANGELOG).

        field_allowed_in(A|B, C) returns true only if the field is allowed in C and either A or B.

        Undef is returned for non-official fields.

### field_transfer_single
        If appropriate, copy the value of the field named $field taken from the $from [Dpkg::Control](https://www.chedong.com/phpMan.php/perldoc/Dpkg%3A%3AControl/markdown)
        object to the $to [Dpkg::Control](https://www.chedong.com/phpMan.php/perldoc/Dpkg%3A%3AControl/markdown) object.

        Official fields are copied only if the field is allowed in both types of objects. Custom
        fields are treated in a specific manner. When the target is not among CTRL_PKG_SRC,
        CTRL_PKG_DEB or CTRL_FILE_CHANGES, then they are always copied as is (the X- prefix is
        kept). Otherwise they are not copied except if the target object matches the target
        destination encoded in the field name. The initial X denoting custom fields can be followed
        by one or more letters among "S" (Source: corresponds to CTRL_PKG_SRC), "B" (Binary:
        corresponds to CTRL_PKG_DEB) or "C" (Changes: corresponds to CTRL_FILE_CHANGES).

        Returns undef if nothing has been copied or the name of the new field added to $to
        otherwise.

### field_transfer_all
        Transfer all appropriate fields from $from to $to. Calls field_transfer_single() on all
        fields available in $from.

        Returns the list of fields that have been added to $to.

### field_ordered_list
        Returns an ordered list of fields for a given type of control information. This list can be
        used to output the fields in a predictable order. The list might be empty for types where
        the order does not matter much.

    ($source, $version) = field_parse_binary_source($ctrl)
        Parse the Source field in a binary package control stanza. The field contains the source
        package name where it was built from, and optionally a space and the source version enclosed
        in parenthesis if it is different from the binary version.

        Returns a list with the $source name, and the source $version, or undef or an empty list
        when $ctrl does not contain a binary package control stanza. Neither $source nor $version
        are validated, but that can be done with [Dpkg::Package::pkg_name_is_illegal](https://www.chedong.com/phpMan.php/perldoc/Dpkg%3A%3APackage%3A%3Apkgnameisillegal/markdown)() and
        [Dpkg::Version::version_check](https://www.chedong.com/phpMan.php/perldoc/Dpkg%3A%3AVersion%3A%3Aversioncheck/markdown)().

### field_list_src_dep
        List of fields that contains dependencies-like information in a source Debian package.

### field_list_pkg_dep
        List of fields that contains dependencies-like information in a binary Debian package. The
        fields that express real dependencies are sorted from the stronger to the weaker.

### field_get_dep_type
        Return the type of the dependency expressed by the given field. Can either be "normal" for a
        real dependency field (Pre-Depends, Depends, ...) or "union" for other relation fields
        sharing the same syntax (Conflicts, Breaks, ...). Returns undef for fields which are not
        dependencies.

### field_get_sep_type
        Return the type of the field value separator. Can be one of FIELD_SEP_UNKNOWN,
        FIELD_SEP_SPACE, FIELD_SEP_COMMA or FIELD_SEP_LINE.

### field_register
        Register a new field as being allowed in control information of specified types. %opts is
        optional

### field_insert_after
        Place field after another one ($ref) in output of control information of type $type.

### field_insert_before
        Place field before another one ($ref) in output of control information of type $type.

## CHANGES
  Version 1.01 (dpkg 1.21.0)
    New function: field_parse_binary_source().

  Version 1.00 (dpkg 1.17.0)
    Mark the module as public.