## ExifTool Object Data Members

The following table lists the data members of the ExifTool object. (If this was C++, these would be documented next to the definitions in the header file, but this is Perl, so I couldn't do that...)

Aside from the variables defined below, there may be other temporary variables added by individual modules. Temporary variables are identified by at least one lower case letter in their name, and are deleted automatically before reading or writing each new image. Make, Model and CameraType are temporary variables like this, but these three are special because they are initialized to an empty string instead of being deleted at the start of processing for each image, which allows them to be tested without having to check for an undefined value.

> Name | Description
> --- | ---
> ADD_DIRS | Hash of parent directories for each directory added during writing (Note: entry may exist but be undefined for top-level directory!) To avoid adding a directory twice, entries may be deleted from this lookup, but only AFTER WriteDirectory() is called.
> BASE | Absolute position of current image in containing file (for example, when processing JPEG image in FujiFilm RAF file)
> BOTH | Reference to HASH of ValueConv/PrintConv arrays, saved for tags when GetValue is called for 'Both' values, and used to avoid having to recalculate both values again (which speeds up building the Composite tags because often the same tag is Require'd by multiple Composite tags).
> CameraType | Camera type used for decoding some Olympus tags
> CHANGED | Number of tags changed during writing
> CHARSET | Lookup table for current Charset setting
> CHECK_WARN | Used to return CHECK_PROC warnings
> COMP_KEYS | Lookup for tag keys used in Composite tags
> Compression | Compression for current EXIF IFD (or '' if no Compression tag). Valid only in EXIF directories for tags after 0x0103.
> CUR_LANG | Hash reference for localized language lookup corresponding to current 'Lang' options setting.
> CUR_WRITE_GROUP | Current family 1 group while writing. Currently used only when writing QuickTime tracks.
> DEL_GROUP | Hash of groups to delete. Value is 1 to delete group completely, or 2 if tags were added back after deleting the group. May have a leading "-" if excluded from a delete.
> DEL_PREVIEW | Flag to delete preview from after JPEG EOI
> DemoteErrors | Errors are demoted to warnings and this count is incremented if non-zero to begin with
> DIR_COUNT | Hash reference for counters of various types of directorys (ICC, IPTC,...)
> DIR_NAME | Name of directory currently being processed
> DOC_COUNT | Number of top-level embedded sub-documents processed while extracting, or 0 if none were processed
> DOC_NUM | Current document number while extracting (0, '' or undef for the main document). May contain a hyphen for sub-subdocuments (eg. '2-3-2').
> DoneID3 | Set to 1 if audio file was scanned for ID3, or 2 if there was an ID3v1 trailer found
> DropTags | Flag to exclude "Drop" tags when writing
> DUPL_TAG | Hash of last used tag key index numbers for each duplicate tag.
> EDIT_DIRS | Hash of parent directories for each directory edited during writing (Note: entry may exist but be undefined for top-level directory!)
> ESCAPE_PROC | Routine for XML or HTML escaping if Escape option is set
> EXCL_TAG_LOOKUP | Hash for looking up excluded tags (keys are lower case tag names)
> EXIF_DATA | EXIF data block (valid while reading from file)
> EXIF_POS | Position of EXIF data in file
> FILENAME | Name of input file while extracting (only if we opened it, '' otherwise)
> FILE_ORDER | Hash of numbers to give the sequence the tags were extracted from file, keyed by tag key
> FILE_EXT | Upper-case file extension (JPG, PEF, AVI, etc...) May be undefined if file has no extension.
> FILE_SEQUENCE | File sequence number when extracting information
> FILE_TYPE | Root file format type (JPEG, TIFF, RIFF, etc...)
> FileType | Actual identified file type
> FIRST_EXIF_POS | Position of first EXIF in file
> FMT_EXPR | The current advanced formatting expression when interpolating tag values in a string. This member allows the formatting expression to be accessed in the ValueConv function of user-defined Composite tags, which provided a mechanism for arguments to be passed to the ValueConv function.
> FORCE_WRITE | Hash reference for metadata types that are being forced to be rewritten (see Extra ForceWrite tag)
> FOUND_DIR | Names of directories found in file (used by Validate feature)
> FOUND_TAGS | Found tags with proper case and order
> GLOBAL_TIME_OFFSET | Time offset hash for first shifted date/time value of GlobalTimeShift option
> HTML_DUMP | Reference to HtmlDump object when using HtmlDump feature
> INDENT | Indent string for verbose output
> IN_RESOURCE | Flag indicates we are processing the resource fork of a Mac OS file
> IO_TAG_LIST | List for output of requested tags in proper case and order
> IsWriting | Flag set to indicate that metadata is being written to this file
> LIST_TAGS | Hash of tag keys by tagInfo reference for active list-type tags. This hash is cleared at the start of processing for each directory. Not used during when writing.
> LOW_PRIORITY_DIR | Lookup based on directory name for directories where undefined Priority tags get set to Priority 0 (eg. PreviewIFD in all images, and IFD1 in JPEG images). This is equivalent to setting PRIORITY to 0 for the tag table only for a specific directory name. A '*' entry in the lookup causes the priority of tags in any directory to be lowered.
> Make | Camera make set during reading and writing
> MAKER_NOTE_BYTE_ORDER | Byte order of extracted maker notes if extracted as a block.
> MAKER_NOTE_INFO | Used by Image::ExifTool::CanonRaw as temporary storage for maker note information when synthesizing maker notes from CRW file with the MakerNotes option.
> MAKER_NOTE_FIXUP | Fixup information for maker notes extracted with the MakerNotes option (unless MakerNotes option is 2). Used by SetNewValuesFromFile() to adjust offsets in maker note IFD
> Model | Camera model name set during reading and writing
> MOVED_KEY | Tag key of last tag replaced by a higher priority tag in a call to FoundTag().
> NEW_VALUE | Hash of new value information keyed by tag info reference. Elements of new value information hash are:
> TagInfo | - | tag information reference
> DelValue | - | list of specific values to delete
> Value | - | list of values to add
> IsCreating | - | must be set for the tag to be added, otherwise just changed if it already exists. A value of 2 will create a new tag if its group already exists, but won't add a new group
> Next | - | reference to next new value hash in linked list if there is more than one new value hash (for writing to different groups) for this tagInfo
> Save | - | flag set by call to SaveNewValues() if this value should be saved
> NewIPTCDigest | MD5 digest for most recently written IPTC data (undefined if IPTC doesn't exist or if it was deleted). Calculated only if a value of 'new' is being written/deleted to/from the Photoshop:IPTCDigest tag
> NO_LIST | Set if List tags shouldn't be accumulated into a list. Undefined to accumulate lists as usual, or 0 to accumulate lists in TAG_EXTRA "NoList" element (and set a TAG_EXTRA "NoListDel" flag for tags that wouldn't have been created).
> NO_STRUCT | Set if structures shouldn't be restored for this metadata. Used to avoid restoring structures for non-XMP (eg. XML) information.
> NO_STRUCT_WARN | Set if structures warnings should be ignored when rebuilding structures (for questionable XML).
> NO_UNKNOWN | Don't generate unknown tags automatically even if Unknown option is set
> NUM_FOUND | Number of tags found
> OldIPTCDigest | MD5 digest for original IPTC data (undefined if IPTC didn't exist). Calculated only if a value of 'old' is being written/deleted to/from the Photoshop:IPTCDigest tag
> OPTIONS | ExifTool options
> PATH | List reference to SubDirectory path. eg) [qw(JPEG APP13 Photoshop IPTC)]
> PDF_CAPTURE | Used by PDF module to store information when writing
> PreferredGroup | Preferred family 1 group for writing tags to the current file. Not defined to use the default group priorities. Set in call to InitWriteDirs().
> PREVIEW_INFO | Information about preview image used while writing JPEG images only. This is a reference to a hash with the following entries:
> Absolute | - | flag set if PreviewImage pointer is relative to the start of file
> BaseShift | - | shift for base of pointer offsets
> Data | - | data for PreviewImage to be written (may either be data for the old or new image, or 'LOAD_PREVIEW' to indicate that the data must be loaded from outside the EXIF segment)
> Fixup | - | [mandatory] fixup for PreviewImage pointers when writing JPEG images
> IsShort | - | flag indicates PreviewImage pointers are 2-byte (instead of 4-byte) integers
> IsTrailer | - | flag indicates image should always be written as a JPEG trailer, even if it fits inside the APP1 EXIF segment (as with Samsung STMN maker notes)
> Relative | - | flag to indicate that pointer offsets are relative
> PRIORITY | Hash of tag Priority values for current tag, keyed by tag name (not tag key!)
> PRIORITY_DIR | Name of priority directory (ie. the IFD for the full resolution image)
> PROCESSED | Reference to hash of address/directory names which were processed during reading and/or writing
> RAF | Random access file object for reading from input file
> RATIONAL | Hash of rational values as a string fraction keyed by tag key
> Recreated | Directories recreated when writing (used to prevent recreating multiple directories of the same type)
> REQUESTED_TAGS | List of requested tags in original case
> REQ_TAG_LOOKUP | Hash for looking up requested tags (keys are lower case tag names)
> SAVE_COUNT | Counts number of times SaveNewValues() has been called
> SAVE_DEL_GROUP | Hash of saved DEL_GROUP entries
> SAVE_NEW_VALUE | Hash of new value information which was overwritten after a call to SaveNewValues()
> SaveFormat | Hash reference to check which TIFF format types were used in the file. Valid only if the (undocumented) SaveFormat option is used.
> SET_GROUP0 | Value to use for family 0 group name when new tags are found
> SET_GROUP1 | Value to use for family 1 group name when new tags are found. May start with a '+' sign to add to existing group name
> SubfileType | SubfileType for current EXIF IFD (or '' if no SubfileType tag). Valid only in EXIF directories for tags after 0x00fe.
> TAG_EXTRA | Hash of extra tag information keyed by tag key. Current extra information may include:
> G0 | - | override for family 0 group name
> G1 | - | dynamic family 1 group name (eg. IFD name or XMP namespace), with a leading '+' to add value to the existing group 1 name
> G3 | - | number for embedded documents (eg. 1, 2, etc)
> TAG_INFO | Hash of tagInfo hash references, keyed by tag key
> TAGS_FROM_FILE | Flag used during extraction when called from SetNewValuesFromFile(). Test this flag when extracting tags that are not normally extracted.
> TIFF_END | Location of end of regular TIFF file set by WriteExif()
> TIFF_TYPE | Type of TIFF data, only set if FILE_TYPE is TIFF. Valid values are APP1, APP3, TIFF, CR2, MRW, JP2, JPX, NEF, PEF, ORF, DNG, etc.
> Validate | Flag to do extra validation checks
> VALUE | Hash of raw tag values keyed by tag key
> WARNED_ONCE | Hash of warning messages that have been issued once already
> WRITE_GROUPS | List of write groups in order of priority
> WRITE_PRIORITY | Hash of write priority values keyed by group name
> WRITTEN | Hash of tags written (currently used only for filesystem date/time tags)
> XMP_CAPTURE | Hash of tag information (value, attribute hash) keyed by XMP property path, used by XMP module during writing
> XMP_ERROR | Error string used by XMP module during writing
> XMP_NS | Hash of URI's keyed by namespace prefix, used by XMP module during writing to remember all used namespaces

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