How can we send user input taken from UI to commandline and run a command using objective c -

i want reset mac osx password , want gui. know in terminal have run following command.

  aug4-2:~ root# passwd   changing password root   new password:   retype new password: 

for want provide user interface, user can reset user password. need use nstask , nspipe task. if 1 have code snippet please post here

try using apple script.

tell application "system events"     activate     display dialog "please enter old password:" default answer "" title "password reset" hidden answer     set pswd0 text returned of result end tell tell application "system events"     activate     display dialog "please enter new password:" default answer "" title "password reset" hidden answer     set pswd1 text returned of result end tell tell application "system events"     activate     display dialog "please re-enter new password:" default answer "" title "password reset" hidden answer     set pswd2 text returned of result end tell if pswd1 = pswd2     if pswd1 = pswd0         display dialog "both passwords entered same" title "password reset"     return      end if else     display dialog "re entered password different" title "password reset"      return end if try     shell script "dscl . -passwd  /users/$user  " & quoted form of pswd0 & "       " & quoted form of pswd1 & " "  on error errmsg number errornumber      if 10 = errornumber         display dialog "old password entered incorrect" title "password reset"          return     else         if 90 = errornumber             display dialog "new password not meeting password policy requirements, password length small" title "password reset"              return         else             if 93 = errornumber                 display dialog "new password not meeting password policy requirements ,it should consist of atleast 1 numeric character" title "password reset"                  return             end if         end if     end if     return end try display dialog "password changed succesfully" title "password reset" return true