user618677 user618677 - 1 year ago 84
C Question

Converting string to integer C

I am trying to find out if there is an alternative way of converting string to integer in C.

I regularly do the following in my code.

char s[] = "45";

int num = atoi(s);

So, is there a short way or another way?

Answer Source

There is strtol which is better IMO. Also I have taken a liking in strtonum, so use it if you have it (but remember it's not portable):

long long
     strtonum(const char *nptr, long long minval, long long maxval,
     const char **errstr);


You might also be interested in strtoumax and strtoimax which are standard functions in C99. For example you could say:

uintmax_t num = strtoumax(s, NULL, 10);
if (num == UINTMAX_MAX && errno == ERANGE)
    /* Could not convert. */

Anyway, stay away from atoi:

The call atoi(str) shall be equivalent to:

(int) strtol(str, (char **)NULL, 10)

except that the handling of errors may differ. If the value cannot be represented, the behavior is undefined.

Recommended from our users: Dynamic Network Monitoring from WhatsUp Gold from IPSwitch. Free Download