Linux当中判断两个文件夹是否相同

作业中遇到的问题：怎么判断Linux当中两个文件夹是否完全相同？

$ diff -u/-r/-N/-a dir1 dir2
　　-a Treat all files as text and compare them line-by-line, even if they do not seem to be text.
　　-N, --new-file
　　　　In directory comparison, if a file is found in only one directory, treat it as present but empty in the other directory.
　　-r When comparing directories, recursively compare any subdirectories found.
　　-u Use the unified output format.

建议使用-r，比较符合逻辑。

效果如图。