If you have a file with @ sign at end, this is how to remove extended attributes on the Mac OS.
Example.
ls -l -rwxr-xr-x@ 4 username staff 128 Mar 24 10:51 sample.txt |
Remove extended attributes.
xattr -c sample.txt |
Result
ls -l -rwxr-xr-x 4 username staff 128 Mar 24 10:51 sample.txt |