C语言中的strspn()函数

strspn()函数返回str1指向的字符串的初始子字符串的长度，该字符串仅由str2指向的字符串包含的那些字符。

句法 ：

size_t strspn(const char *str1, const char *str2)
str1 : string to be scanned.
str2 : string containing the 
characters to match.
Return Value : This function
returns the number of characters
in the initial segment of str1 
which consist only of characters 
from str2.

// C program to illustrate strspn() function
#include 
#include 
  
int main () {
   int len = strspn("geeks for geeks","geek");
   printf("Length of initial segment matching : %d\n", len );    
   return(0);
}

输出：

Length of initial segment matching 4

// C program to illustrate strspn() function
#include 
#include 
  
int main () {
   int len = strspn("i am","xyz");
   printf("Length of initial segment matching : %d\n", len );
   return(0);
}

输出：

Length of initial segment matching 0

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