Identify a file for encryption or decryption

Dear Members,

Can we find if a particular file is encrypted or decrypted.

I need a command by which i should be able to identify if a file is encrypted or decrypted.

How can we do this?

There are so many ways to encrypt a file.

For this reason, it is not really feasible to have a simple command to determine if the file is encrypted.

For example, how about an encryption scheme where you simply shift each letter of the alphabet to the right by 8 characters? Or how about if the encryption scheme is to substitute each letter based on a one time pad?

So, you need to be very specific when discussing "encrypted files".