The atoi() function converts the initial portion of the string pointed to
by nptr to int. The behaviour is the same as
strtol(nptr, (char **)NULL, 10);
except that atoi() does not detect errors.
The atol() and atoll() functions behave the same as atoi(),
except that they convert the initial portion of the string to their return
type of long or long long. atoq() is an obsolete name for
The non-standard atoq() function is not present in libc 4.6.27 or glibc
2, but is present in libc5 and libc 4.7 (though only as an inline function in
<stdlib.h> until libc 5.4.44). The atoll() function is
present in glibc 2 since version 2.0.2, but not in libc4 or libc5.