code to "sniff" file header to determine file type

[dgibson5531]

I need to develop some code to check the header type of a file attachment to determine the file extension. This will be a picture file attachment, so I need to determine whether this is a .jpeg or bitmap etc. Can someone give me some idea how to code this ?

[Yona Low]

Search google for "file formats for programmers", and you'll find excellent results on this topic