C Programming/C Reference/string.h/strstr

strstr is a C standard library string function as defined in string.h. strstr() has the function signature char * strstr(const char *haystack, const char *needle); which returns a pointer to a character at the first index where needle is in haystack, or NULL if not present.

The strcasestr() is a function much like strstr() except that it ignores the case of both needle and haystack. strcasestr() is a non-standard function while strstr() conforms to C89 and C99.

Example

#include <stdio.h>
#include <string.h>
 
int main(void) 
{
        /* Define a pointer of type char, a string and the substring to be found*/
        char *cptr;
        char str[] = "Wikipedia, be bold";
        char substr[] = "edia, b";
 
        /* Find memory address where substr "edia, b" is found in str */
        cptr = strstr(str, substr);
 
        /* Print out the character at this memory address, i.e. 'e' */
        printf("%c\n", *cptr);
 
        /* Print out "edia, be bold" */
        printf("%s\n", cptr);
 
        return 0;
}

cptr is now a pointer to the sixth letter (e) in "wikipedia".

See also

• strchr

External links

• C++ reference for std::strstr