The getpass function displays a prompt to, and reads in a password from, /dev/tty. If this file is not accessible, getpass displays the prompt on the standard error output and reads from the standard input.
The password may be up to _PASSWORD_LEN (currently 128) characters in length. Any additional characters and the terminating newline character are discarded.
The getpass function turns off character echoing while reading the password.
The getpass function returns a pointer to the null terminated password.