boobaa@jabitha:~/data/foo$ cat z.c
#include <stdlib.h>
#include <stdio.h>      // stderr

int main() {
        write(stdout, "foo\n");
        return 0;
}
boobaa@jabitha:~/data/foo$ gcc -Wall z.c
z.c: In function 'main':
z.c:5: warning: implicit declaration of function 'write'
boobaa@jabitha:~/data/foo$