ExifTool [CMD]

I found it mentioned only once in the forum, without details, so I thought, since I (re-)discovered it yesterday, that I should post here to advertize it more...
ExifTool by Phil Harvey is a superb command line utility to read, create, delete or change metadata in a variety of files and format: Exif, of course, but also IPTC, the modern XMP by Adobe, PNG tEXt chunks, even MP3's ID3 tags!
You probably won't find a more complete tool.
This has a cost: it weights 2.7MB, which is quite big for a command line utility. But given the range of stuff it understands, this is understandable. That, and the fact it is actually a Perl script transformed (on Windows) to a standalone executable... Perl isn't a small scripting language...
And it has some learning curve. But it looks perfect for batch tagging!

Check the site, the tool is free!

i just (re)found theExif-Tool and am amazed:
I like to point out , that it does not only read Exif-Metadata
but a lot more, including PDF-Metadata.

And it features a very cool idea that could be used in ahk-scripts as well:
it parses its own filename and reconfigures depending on that.

This stand-alone Windows version allows simple command-line options to
be added to the name of the executable (in brackets and separated by
spaces at the end of the name), providing a mechanism to use options
when launched via the mouse. For example, changing the executable name
to "exiftool(-a -u -g1 -w txt).exe" gives a drag-and-drop utility which
generates sidecar ".txt" files with detailed meta information. As
shipped, the -k option is added to cause exiftool to pause before
terminating (to keep the command window open). Options may also be added
to the "Target" property of a Windows shortcut to the executable.

Here is a list of the supported file-types:

File Type Support Description
3FR R Hasselblad RAW (TIFF-based)
ACR R American College of Radiology ACR-NEMA (DICOM-like)
AFM, ACFM, AMFM R Adobe [Composite/Multiple Master] Font Metrics
AI R/W Adobe Illustrator (PS or PDF)
AIFF, AIF, AIFC R Audio Interchange File Format
APE R Monkey's Audio
ARW R/W Sony Alpha RAW (TIFF-based)
ASF R Microsoft Advanced Systems Format
AVI R Audio Video Interleaved (RIFF-based)
BMP, DIB R Windows BitMaP / Device Independent Bitmap
BTF, TIFF, TIF R BigTIFF (64-bit Tagged Image File Format)
COS R Capture One Settings (XML-based)
CR2 R/W Canon RAW 2 (TIFF-based)
CRW, CIFF R/W Canon RAW Camera Image File Format (CRW specification)
CS1 R/W Sinar CaptureShop 1-shot RAW (PSD-based)
DCM, DC3, DIC, DICM R DICOM - Digital Imaging and Communications in Medicine
DCP R/W DNG Camera Profile (DNG-like)
DCR R Kodak Digital Camera RAW (TIFF-based)
DFONT R Macintosh Data Fork Font
DIVX R DivX media format (ASF-based)
DJVU, DJV R DjVu image (AIFF-like)
DNG R/W Digital Negative (TIFF-based)
DOC, DOT R Microsoft Word Document/Template (FPX-like)
DOCX, DOCM R Office Open XML Document [Macro-enabled]
DOTX, DOTM R Office Open XML Document Template [Macro-enabled]
DYLIB R Mac OS X Mach-O executable and library files
EIP R Capture One Enhanced Image Package (ZIP-based)
EPS, EPSF, PS R/W [Encapsulated] PostScript Format
ERF R/W Epson RAW Format (TIFF-based)
EXE, DLL R DOS/Windows executable and library files
EXIF R/W/C Exchangable Image File Format metadata (TIFF-based)
F4A, F4B, F4P, F4V R Adobe Flash Player 9+ Audio/Video (Quicktime-based)
FLA R Macromedia/Adobe Flash project (FPX-like)
FLAC R Free Lossless Audio Codec
FLV R Flash Video
FPX R FlashPix image
GIF R/W Compuserve Graphics Interchange Format
GZ, GZIP R GNU ZIP compressed archive
HDP, WDP R/W Windows HD Photo / Media Photo (TIFF-based)
HTML, HTM, XHTML R [Extensible] HyperText Markup Language
ICC, ICM R/W/C International Color Consortium color profile
IIQ R Phase One Intelligent Image Quality RAW (TIFF-based)
IND, INDD, INDT R/W Adobe InDesign Document/Template (XMP metadata only)
ITC R iTunes Cover Flow artwork
JP2, JPX R/W JPEG 2000 image
JPEG, JPG R/W Joint Photographic Experts Group image (see table below)
K25 R Kodak DC25 RAW (TIFF-based)
KDC R Kodak Digital Camera RAW (TIFF-based)
KEY, KTH R Apple iWork '09 Keynote presentation/Theme
LNK R Microsoft Shell Link (Windows shortcut)
M2TS, MTS, M2T R MPEG-2 Transport Stream (used for AVCHD video)
M4A, M4B, M4P, M4V R MPEG-4 Audio/Video (Quicktime-based)
MEF R/W Mamiya (RAW) Electronic Format (TIFF-based)
MIE R/W/C Meta Information Encapsulation (MIE specification)
MIFF, MIF R Magick Image File Format
MKA, MKV, MKS R Matroska Audio/Video/Subtitle
MOS R/W Creo Leaf Mosaic (TIFF-based)
MOV, QT R Apple QuickTime Movie
MP3 R MPEG-1 layer 3 audio (uses ID3 information)
MP4 R Motion Picture Experts Group version 4 (Quicktime-based)
MPC R Musepack Audio
MPEG, MPG, M2V R Motion Picture Experts Group version 1 or 2
MPO R/W Extended Multi-Picture format (JPEG with MPF extensions)
MQV R Sony Mobile QuickTime Video
MRW R/W Minolta RAW
NEF R/W Nikon (RAW) Electronic Format (TIFF-based)
NMBTEMPLATE R Apple iWork '09 Numbers Template
NRW R/W Nikon RAW (2) (TIFF-based)
NUMBERS R Apple iWork '09 Numbers spreadsheet
ODP, ODS, ODT R Open Document Presentation/Spreadsheet/Text (ZIP/XML-based)
OGG R Ogg Vorbis and Ogg FLAC audio
ORF R/W Olympus RAW Format (TIFF-based)
OTF R Open Type Font
PAGES R Apple iWork '09 Pages document
PDF R/W Adobe Portable Document Format
PEF R/W Pentax (RAW) Electronic Format (TIFF-based)
PFA, PFB R PostScript Font ASCII/Binary
PFM R Printer Font Metrics
PICT, PCT R Apple Picture file
PMP R Sony DSC-F1 Cyber-Shot image
PNG, JNG, MNG R/W Portable/JPEG/Multiple-image Network Graphics
PPM, PBM, PGM R/W Portable Pixel/Bit/Gray Map
PPT, PPS, POT R Microsoft PowerPoint Presentation/Slideshow/Template (FPX-like)
POTX, POTM R Office Open XML Presentation Template [Macro-enabled]
PPSX, PPSM R Office Open XML Presentation Slideshow [Macro-enabled]
PPTX, PPTM R Office Open XML Presentation [Macro-enabled]
PSP, PSPIMAGE R Paint Shop Pro
THMX R Office Open XML Theme
PSD, PSB R/W PhotoShop Drawing / Large Document
QTIF, QTI, QIF R QuickTime Image File
RA R Real Audio
RAF R/W FujiFilm RAW Format
RAM, RPM R Real Audio/Plug-in Metafile
RAW R Kyocera Contax N Digital RAW
RAW R/W Panasonic RAW (TIFF-based)
RIFF, RIF R Resource Interchange File Format
RM, RV, RMVB R Real Media/Video [Variable Bitrate]
RSRC R Mac OS Resource
RTF R Rich Text Format
RW2 R/W Panasonic RAW 2 (TIFF-based)
RWL R/W Leica RAW (TIFF-based)
RWZ R Rawzor compressed image
SO R Unix ELF executable and Shared Object files
SR2 R/W Sony RAW 2 (TIFF-based)
SRF R Sony RAW Format (TIFF-based)
SRW R/W Samsung RAW format (TIFF-based)
SVG R Scalable Vector Graphics (XML-based)
SWF R Shockwave Flash
THM R/W Canon Thumbnail (JPEG)
TIFF, TIF R/W Tagged Image File Format
TTF, TTC R True Type Font/Collection
VOB R Video Object (MPEG-based)
VRD R/W/C Canon DPP Recipe Data
WAV R Windows digital audio WAVeform (RIFF-based)
WMA, WMV R Windows Media Audio/Video (ASF-based)
X3F R Sigma/Foveon RAW
XLS, XLT R Microsoft Excel Spreadsheet/Template (FPX-like)
XLSX, XLSM, XLSB R Office Open XML Spreadsheet [Macro-enabled/Binary]
XLTX, XLTM R Office Open XML Spreadsheet Template [Macro-enabled]
XMP R/W/C Extensible Metadata Platform sidecar file
ZIP R ZIP archive