Example: lr_param_sprintf

int index = 56;
char * suffix = "txt";

lr_param_sprintf ("LOG_NAME_PARAM", "log_%d.%s", index, suffix,100);

lr_output_message("The new file name is %s",
    lr_eval_string("{LOG_NAME_PARAM}"));

Example: Output:
Action.c(9): The new file name is log_56.txt