Definition and Usage
Encrypts the string EXPR using the system crypt( ) function. The value of SALT is used to select an encrypted version from one of a number of variations. Note that there is no equivalent decryption function. You cannot decrypt a string that has been encrypted in this way. It’s normally used one way, first to encrypt a string, and then to encrypt a password to compare against the encrypted string. If you’re using it in this form, then consider supplying the encrypted password as the SALT.
Here’s an example that makes sure that whoever runs this program knows their password: