Best way to scan string for a number?

My string input can either be "-c123" or "-c 123".

What's the best way to scan the string to get the number out?

If you don't need tight control, try atoi().
If you want tighter control of errors, prefer strtol().

Read the function descriptions!!!

Code:

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char input1[] = "-c123";
char input2[] = "-c 123";
int val1atoi = atoi(input1 + 2);
int val2atoi = atoi(input2 + 2);

char *err;
errno = 0; int val1strtol = strtol(input1 + 2, &err, 10); /* test *err, val1strtol, and errno */
errno = 0; int val2strtol = strtol(input2 + 2, &err, 10); /* test *err, val2strtol, and errno */

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You can also use sscanf() withy a littel more control than atoi() and a little less than strtol() ...

Code:

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char input[] = "-c 123";
int val;
if (sscanf(input, "-c%d", &val) != 1) /* error */;

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All 3 funtions above properly ignore whitespace.

thanks a ton. I was messing around with sscanf() but didn't really wrap my head around it.