String : strspn and strcspn

Question

 strspn and strcspn

Answer 1

Given a string, strspn calculates the length of the initial substring (span) consisting solely of a specific list of characters. strcspn is similar, except it calculates the length of the initial substring consisting of any characters except those listed:

/*  Provided a string of "tokens" delimited by "separators", print the tokens along  with the token separators that get skipped. */

#include <stdio.h>

#include <string.h>

int main(void)

{    

const char sepchars[] = ",.;!?";    

char foo[] = ";ball call,.fall gall hall!?.,";    

char *s;    

int n;

for (s = foo; *s != 0; /*empty*/)

{                   /* Get the number of token separator characters. */        

n = (int)strspn(s, sepchars);

if (n > 0)            

printf("skipping separators: << %.*s >> (length=%d)\n", n, s, n);

        /* Actually skip the separators now. */        

s += n;

        /* Get the number of token (non-separator) characters. */        

n = (int)strcspn(s, sepchars);

if (n > 0)            

printf("token found: << %.*s >> (length=%d)\n", n, s, n);

        /* Skip the token now. */        

s += n;    

}

printf("== token list exhausted ==\n");

return 0;

}

Analogous functions using wide-character strings are wcsspn and wcscspn; they're used the same way.