The AbcExport plugin is used to write an Alembic file.
It contains a single command named AbcExport.  It isn't a file
translator so it can write out multiple files with different settings while only
stepping through the frame range once.

To write out the entire scene from frame 1 to 100:
AbcExport -j "-fr 1 100 -file scene.abc";

To write out only your selected shapes (and it's ancestor nodes):
AbcExport -j "-sl -file scene.abc";

Other options can be viewed via:
AbcExport -h;