If you have a file with @ sign at end, this is how to remove extended attributes on the Mac OS.

Example.

<pre lang="bash">
ls -l
-rwxr-xr-x@  4 username  staff   128 Mar 24 10:51 sample.txt

Remove extended attributes.

<pre lang="bash">
xattr -c sample.txt

Result

<pre lang="bash">
ls -l
-rwxr-xr-x  4 username  staff   128 Mar 24 10:51 sample.txt