Getting The User's Name

To get the name of the user which we sohuld authenticate:
extern int pam_get_user(pam_handle_t *pamh,
                                  const char **user,
                                  const char *prompt);

This function will cause the pam library to return the user name, in the following manner:
Get the 'PAM_USER' item. If it is defined, return this in '*user'.
Otherwise, use the conversation function to prompt the user with the given prompt, and return whatever they typed. Set this new value in the 'PAM_USER' item.

Note that the '*user' string should NOT be freed by the module. It will be freed by the PAM library on the next call to pam_get_user, or when the application ends the PAM session.