I'd use a while loop with strchr().
Code:
char string[] = { "I like this string" }; //note the double spaces around the word this
char *ptr, ch = '"'; //a double quote surrounded by single quotation marks
int where, i, j;
string[7] = '"'; //now we add the double quotation marks
string[12] = '"';
while (ptr = strchr(string, ch) ) {
//print where it is
where = ptr - string;
printf("\n Double quotation marks were found at %d", where);
//slide all the chars after the location of where, to the left by one char
for(i = where, j = strlen(string); i < j; i++)
string[i] = string[i + 1];
}
I haven't run the above code, but it should be close if not perfect. You'll want to include string.h, of course.