I want to search for string/expression in some c files using **grep** or find. Is there any ways to search in header files which is included in that c file?

eg:

myfile.c
--------

```
#include <stdio.h>
#include "myfile1.h"
#include "myfile2.h"

void main()
{
   DATA val;  
}

```

Let I want to search for string "DATA". It should search in myfile.c and in myfile1.h,myfile2.h...