在Unix系统上，两者都将返回true-在Unix中，所有内容都是文件，包括目录.但是要测试该名称是否被采用，您应该同时检查两者.可能会有一个名为"foo"的常规文件，这将阻止您创建目录名称"foo".

Both would return true on Unix systems - in Unix everything is a file, including directories. But to test if that name is taken, you should check both. There might be a regular file named 'foo', which would prevent you from creating a directory name 'foo'.