c code to change current user password using PAM API

["ashish yadav" <ashishyadav78 gmail com>]

Hi,
 I want to write c code to change current user password.
The code first check for current password & then set new password.
The code must use PAM API just like passwd utility.
Also code must work without user intervention ie only by argument current password & new password are given.
So, can any one know that already this work is done  or  i can use  passwd  utility in my c code using system command.

Thanks.
Ashish Yadav