Why not using svn merge?
Assuming you want to revert from current HEAD (last committed) version to revision 268:
cd folder
svn up
svn merge -r HEAD:268 .
Then resolve any conflicts manually (there should be nothing if there is no local change) and:
svn commit -m "- reverted to revision 268"
To revert single change (e.g. made in revision 666):
cd folder
svn merge -c -666 .
To revert local changes (not committed yet):
cd folder
svn revert -R .