似乎您必须包含< filesystem> 像这样：

It seems you have to include <filesystem> like this:

#include <experimental/filesystem>

别忘了添加 -lstdc ++ fs 作为GCC标志！

Don't forget to add -lstdc++fs as a GCC flag!

这里是证据：
花木

如果这不起作用，则可能意味着您没有文件系统。

If that doesn't work, then that probably means that you don't have filesystem in your configuration.

另外，如@MartinR。指出，在GCC 8+中不再需要 实验性。

Also, as @MartinR. pointed out, the experimental is no longer needed in GCC 8+.