How do I add cover art to an .aiff on OSX from the commandline
Under OS X, I've used Kid3 to add cover art to AIFF files, from both the GUI and CLI with the latter in both direct and interactive modes. The CLI version is not for the faint of heart and you must read the documentation  The Kid3 Handbook (English version) to use the CLI, especially the CLI examples section as it shows something that's not shown elsewhere in the documentation or output of the internal help file of kid3-cli.

Which is the use of single quotes around the commands being used, e.g.:

kid3-cli -c 'select "/path/to/filename.aiff"' -c 'set picture:"/path/to/coverart.jpg" "Picture Description"' -c 'save'


Note that the example above is basic syntax for just setting cover art and /path/to/ can be omitted if everything is in the working directory and "Picture Description" can be "" if no description is wanted, but it has to be supplied one way or the other in this use case.

The kid3-cli executable is within the kid3.app application bundle, e.g. /Applications/kid3.app/Contents/MacOS/kid3-cli and to make it easier to use, you might want to set an alias for it in your bash profile file or set a symlink for it to a location that is within the PATH variable.

Example for your bash profile file:

alias kid3-cli='/Applications/kid3.app/Contents/MacOS/kid3-cli'


Example to create a symlink from Terminal:

sudo ln -s /Applications/kid3.app/Contents/MacOS/kid3-cli /usr/local/bin/kid3-cli


Then from the command line you could use: kid3-cli ...