How to check if a file is gzip compressed?

Question

I have a C / C++ program which needs to read in a file that may or may not be gzip compressed. I know we can use gzread() from zlib to read in both compressed and uncompress

Answer 1

What is the difference in performance between reading compressed and uncompressed files using gzread()?

Anyway, in order to detect if a file is gzipped, you can read the magic number at the beginning of the file, which is 1f 8b according to the link.