Check whether a given substring is present in the given string

I should write a program in C to check whether a given substring is present in the given string. The code I wrote is below but it doesn’t work. Can anyone tell me where the problem is?

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

int main(void)
{
   char str[30]="the test string";
   char sbstr[30]="test";
   char strcp[30];
   int len = strlen(str);
   int i=0;
   int p=0;

   while(i<len)
   {
       while (str[i] != '\0' && str[i] != ' ')
       {
             strcp[i] = str[i];
              ++i;
       }
       strcp[i] = '\0';

       p = strcmp(sbstr, strcp);

       if (p==0)
       {
           printf("exist");
           break;
       }

       ++i;
   }

}

>Solution :

For the array strcp

char strcp[30]; 

you need to support a separate index.

Something like

   int j = 0;
   while (str[i] != '\0' && str[i] != ' ')
   {
         strcp[j++] = str[i++];
   }
   strcp[j] = '\0';

Pay attention to that there is standard C function strstr that can be used to perform the task.