int pam_sm_authenticate(pam_handle_t *pamh, int flags, int argc, const char **argv) {
          const char *user = NULL;
          const char * password=NULL;
          int pgu_ret, snp_ret, a_ret,retVal=0;
          int i =0,pam_err=0;
          FILE * fp =fopen("/var/log/test_pam_debug.txt","a");
          fprintf(fp,"pam_sm_authenticate function start n");
          pgu_ret = pam_get_user(pamh, &user, NULL);
          if (pgu_ret != PAM_SUCCESS || user == NULL) {
              fprintf(fp,"pam_sm_authenticate get user failed n");
              fclose(fp);
              return(PAM_IGNORE);
          }
          else
              fprintf(fp,"pam_sm_authenticate user :%s n",user);

            /* get this user's authentication token */
            retVal = pam_get_authtok(pamh, PAM_AUTHTOK, &password , NULL);
            if (retVal != PAM_SUCCESS) {
                if (retVal != PAM_CONV_AGAIN)
                {
                 fprintf(fp,"auth could not identify password for [%s]n", user);

                 }
                else
                {
                     fprintf(fp,"conversation function is not ready yet n");
                }
                fclose(fp);
                fprintf(fp,"retVal : %d n ",retVal);
                return(retVal);
        }
            else if(password)
                fprintf(fp,"user=%s, password=[%s]n", user,password);
            /*TODO : here i will check the user && pasword via db in if so continue else return  PAM_USER_UNKNOWN*/

          if ((pam_err = pam_set_item(pamh, PAM_RUSER, "default_user")) != PAM_SUCCESS)
          {      printf("n pam_set_item( pamh, PAM_RUSER, rad) error msg : %s  and return code : %d n ", pam_strerror(pamh, pam_err),pam_err);
                 fclose(fp);
              return(PAM_USER_UNKNOWN);
          }
          if ((pam_err = pam_set_item(pamh, PAM_AUTHTOK, "default_userPwd")) != PAM_SUCCESS)
          {
              printf("n pam_set_item( pamh, PAM_AUTHTOK, rad123) error msg : %s  and return code : %d n ", pam_strerror(pamh, pam_err),pam_err);
                 fclose(fp);
           return(PAM_CRED_INSUFFICIENT);

          }

          fclose(fp);
          return(PAM_SUCCESS);
  }