integer extraction from string

Question

I have an input argument string const char* s I know that it starts the sequence of chars which are integers representation ,this sequence could be of any length ,

Answer 1

One way would be to use sscanf:

char *str = "23meeting";
unsigned x;
sscanf(str, "%u", &x);
printf("%u\n", x);

For additional error-checking, though, you'll have to do some additional manual checks.