In this article, you will learn in-depth about C string library function strspn( ) with example and explanation.

strspn( ) is the built in standard string manipulation function that is defined under string handling library string.h.

Therefore it is necessary to include string header file to use standard C string library function strspn( ).

#include<string.h>

Function prototype of C string library function strspn( )

size_t strspn( const char *str1, const char *str2 );

where,

                 str1 = string that needs to be scanned

                 str2 = string which character needs to be matched in str1

This function searches for the characters of string str2 in the string str1.

It returns the length of the initial part of the string str1 that contains only characters from the string str2.

Therefore, it returns an integer value.

How C string library function strspn( ) works?

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Example: C program to demonstrate the use of string library function strspn( )

/*Use of string library function strspn*/

#include<stdio.h>
#include<string.h>

int main()
{
   //initializing char pointers
   const char *str1 = "Learn from trytoprogram.com";
   const char *str2 = "rtyn eaL ofm";

   //displaying both string 
   printf("str1 = %s\n\n", str1);
   printf("str2 = %s\n\n", str2);

   printf("Length of str1 consisting only characters "
          "from str2 = %d\n", strspn( str1, str2 ));

   return 0;

}

Output

Explanation

In the above, function strspn( ) searches for "rtyn eaL ofm" in the string str1.

Thus, it returns the total length of matching characters as shown in the figure above.