--no-clobber

When used in conjunction with the --output, --remote-header-name, --remote-name, or --remote-name-all options, curl avoids overwriting files that already exist. Instead, a dot and a number gets appended to the name of the file that would be created, up to filename.100 after which it does not create any file.

Note that this is the negated option name documented. You can thus use --clobber to enforce the clobbering, even if --remote-header-name is specified.

The --continue-at option cannot be used together with --no-clobber.