OSXFAQ Mac OS X UNIX Tip-of-the-Day 

Today's tip looks at file content metadata. Different types of file content have different types of metadata. Let's pass a photoshop file to mdls:

$ mdls heart.psd
heart.psd -------------
kMDItemAttributeChangeDate     = 2006-01-03 00:21:09 +0000
kMDItemBitsPerSample           = 40
kMDItemColorSpace              = "RGB"
kMDItemContentCreationDate     = 2004-02-06 02:12:09 +0000
kMDItemContentModificationDate = 2004-02-06 02:12:09 +0000
kMDItemContentType             = "com.adobe.photoshop-image"
kMDItemContentTypeTree         = (
    "com.adobe.photoshop-image", 
    "public.image", 
    "public.data", 
    "public.item", 
    "public.content"
)
kMDItemCreator                 = "Adobe Photoshop 7.0"
kMDItemDisplayName             = "heart"
kMDItemFSContentChangeDate     = 2004-02-06 02:12:09 +0000
kMDItemFSCreationDate          = 2004-02-06 02:12:09 +0000
kMDItemFSCreatorCode           = 943868237
kMDItemFSFinderFlags           = 1024
kMDItemFSInvisible             = 0
kMDItemFSIsExtensionHidden     = 1
kMDItemFSLabel                 = 0
kMDItemFSName                  = "jj1.psd"
kMDItemFSNodeCount             = 0
kMDItemFSOwnerGroupID          = 501
kMDItemFSOwnerUserID           = 501
kMDItemFSSize                  = 2204679
kMDItemFSTypeCode              = 943870035
kMDItemHasAlphaChannel         = 1
kMDItemID                      = 923966
kMDItemKind                    = "Adobe Photoshop file"
kMDItemLastUsedDate            = 2006-01-03 00:21:09 +0000
kMDItemLayerNames              = (jan, hair)
kMDItemOrientation             = 0
kMDItemPixelHeight             = 718
kMDItemPixelWidth              = 450
kMDItemResolutionHeightDPI     = 72.00006
kMDItemResolutionWidthDPI      = 72.00006
kMDItemUsedDates               = (2005-11-02 12:18:02 +0000, 2006-01-03 00:00:00 +0000)

The last few items show metadata describing the image size, resolution, and even on what photoshop layers it contains.

Try passing a song file to mdls. The metadata includes the genre, title, and bit rate.

...
kMDItemMediaTypes               = (Sound)
kMDItemMusicalGenre             = "Alternative & Punk"
kMDItemStreamable               = 0
kMDItemTitle                    = "Like It Or Leave It"
kMDItemTotalBitRate             = 191384
...

To extract a specific metadata item, pass the item name as an argument to the name option:

At this point, you might be tempted to form a 'find/xargs/grep' command line to search through, say, all music for songs a particular Genre. But Apple has provided a much better way of doing this...a command line spotlight.

Tomorrow's tip will look at spotlighting on the command line.

A tip to save you life: "Remember to buy her a card!"