How do I check if a string is a valid md5 or sha1 checksum string

Question

I don\'t want to calculate a file\'s checksum, just to know if a given string is a valid checksum

Answer 1

Any 160-bit sequence is a possible SHA1 hash. Any 128-bit sequence is a possible MD5 hash.

If you're looking at the hex string representations of them, then a sha1 will look like 40 hexadecimal digits, and an md5 will look like 32 hexadecimal digits.