JPG Tags - Captions and Descriptions in Picasa and OSX

Picasa and OSX File Info:

• displays xmp:description as the Picasa Caption
  (i.e. if the iptc:caption-abstract happens to be different, it will NOT be displayed.)
• if there is no xmp:description, then they display iptc:caption-abstract

Picasa

• Changing Caption field updates BOTH xmp:description and iptc:caption-abstract

Exiftool commands used in OSX Terminal to change JPG Data

• Add or change xmp:description for a file
• exiftool -xmp:description='This is a new xmp description' dst.jpg
  
• Delete an xmp:description for a file
• exiftool -xmp:description= dst.jpg
  
• Copy the filename to the xmp:description
• exiftool -xmp:description=--filename dst.jpg
  
• Copy xmp:description to iptc:caption-abstract.  Not really necessary as the xmp:description will be displayed in Picasa and OSX File Info
• exiftool "-iptc:caption-abstract
  
• Copy the filename into the xmp:description field for all files in the current directory
• exiftool "-xmp:description
  
• Copy Filename without ".jpg"
• supposed to be able to use a config file to define a new variable "basename". But damned if I can get it to work.
• exiftool "-xmp:description<${filename;s/.jpg/ /}" *.jpg  ----- just gives errors
  
• Useful Terminal Commands
• "pwd" displays current directory (folder)
• "cd" command changes directory (folder). Either type the directory, or drag the folder into the terminal window to automatically type its name.