gpg -b file	create a detached signature of the file
gpg -s -e file	signing a file and encrypting it with public key
You need a passphrase to unlock the secret key for user:
"User Name <user@something.com"
1024-bit DSA key, ID 47D0D9A8, created 2000-01-15
You did not specify a user ID. (you may use "-r")
Enter the user ID: user@something.com

gpg --decrypt file.asc

You need a passphrase to unlock the secret key for
user: "User Name <user@something.com>"
1024-bit ELG-E key, ID 47D0D9A8, created 2000-01-15 (main key ID 39B0D9A8)
===================================== GPG
$ gpg -b file   sign a file with gpg
 
which will create a detached signature of the file.
To verify the signature use "gpg --verify file.sig file". If all is well:
  
$ gpg --verify file.sig file
gpg: Signature made Sat 15 Jan 2000 05:23:31 AM MST using DSA key ID 47D0D9A8
gpg: Good signature from "Kurt Seifried <seifried@securityportal.com>"
   
If someone has fiddled with the file or signature you will see something like:
$ gpg --verify file.sig file
gpg: Signature made Sat 15 Jan 2000 05:23:31 AM MST using DSA key ID 47D0D9A8
gpg: BAD signature from "Kurt Seifried <seifried@securityportal.com>"