I believe you are trying to compare two strings representing values, the function you are looking for is:
int atoi(const char *nptr);
or
long int strtol(const char *nptr, char **endptr, int base);
these functions will allow you to convert a string to an int/long int:
int val = strtol("555", NULL, 10);
and compare it to another value.
int main (int argc, char *argv[])
{
long int val = 0;
if (argc < 2)
{
fprintf(stderr, "Usage: %s number\n", argv[0]);
exit(EXIT_FAILURE);
}
val = strtol(argv[1], NULL, 10);
printf("%d is %s than 555\n", val, val > 555 ? "bigger" : "smaller");
return 0;
}