4.217.34 char * strstr

char * strstr(const char *, const char *) __ATTR_PURE__

The strstr() function finds the first occurrence of the substring s2 in the string s1. The terminating '\0' characters are not compared.

Remember:

The strstr() function returns a pointer to the beginning of the substring, or NULL if the substring is not found. If s2 points to a string of zero length, the function returns s1.