atoi() - convert ASCII string to integer
#include <stdlib.h>
int atoi (const char *nptr)
The atoi(3) function converts the initial portion of the string pointed to by nptr to integer representation.
It is equivalent to:
(int)strtol(nptr, (char **)NULL, 10);
atof(3)
atol(3)
strtod(3)
strtol(3)
strtoul(3)