char * strstr_P(const char *, const char *) __ATTR_PURE__
The strstr_P() function finds the first occurrence of the substring s2 in the string s1. The terminating '\0' characters are not compared. The strstr_P() function is similar to strstr() except that s2 is pointer to a string in program space.
The strstr_P() 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.