One Space
Replace XYZ with your space and tempdir with the directory you want to put the attachments in.
Make sure you create the directory first. Otherwise it will be treated as a file name. If it is a directory, then the attachment name is used as the file name within the directory provided.
--action runFromAttachmentList --space XYZ --common "--action getAttachment --id @pageId@ --name \"@attachment@\" --file tempdir" --continue
All Spaces
Replace tempdir with the directory you want to put the attachments in. This can take a long time on larger sites!!!
--action runFromAttachmentList --space @all --common "--action getAttachment --id @pageId@ --name \"@attachment@\" --file tempdir" --continue
To Avoid Duplicate Attachment Names
Attachment names are only unique for the page they are on, so you might want something more precise.
--action runFromAttachmentList --space @all --common "--action getAttachment --id @pageId@ --name \"@attachment@\" --file \"tempdir/@space@/@title@/@attachment@\" --continue