I've prepared this simple example which is not working for me

#include <stdio.h>
#include <stdlib.h>

FILE *fp;
char filename[] = "damy.txt";

void echo (char[] text)
{
    fp = fopen(filename, "a");
    fwrite(text, 1, strlen(text), fp);
    fclose(fp);
    printf(text);
}

int main ()
{
    echo("foo bar");
    return 0;
}

It's supposed to write both to command window and to file. However, this gives compilation error - the text used in echo() is not declared. Does c need another declaration of the variable?