Question

I want to read data from a string. The string is like this:

"123 35   123 0    0      0       817 0    0   0   0"

there are a few numbers and spaces which is uncertain in the string. I want to read the third number. How to read data?

Answer 1

Use sscanf(). It will skip whitespace.

int a, b, c;
if( sscanf(string, "%d %d %d", &a, &b, &c) == 3)
  printf("the third number is %d\n", c);

You can also use %* to suppress assignment of the two first numbers:

int a;
if( sscanf(string, "%*d %*d %d", &a) == 1)
  printf("the third number is %d\n", a);

Note that sscanf() returns the number of successful conversions (and assignments) it made, which is why the return value must be checked before relying on the values of the output variables.