Generally speaking, two files with the same MD5 value or the same SHA 1 value can be judged as the same file, such as file A and file B. Through a certain algorithm, the MD5 value of A and the MD5 value of B can be obtained. If the MD5 value of A is the same as that of B,,, then A and B are the same file! ! ! (MD5 and SHA 1 have nothing to do with the file name! ) That is to say, it is the same to judge whether the file has been changed, but the algorithm for calculating the MD5 value is different from the algorithm for SHA 1 value, and the effect is the same.