strstr - find a substring
#include <string.h> char *strstr(const char *s1, const char *s2);
The strstr() function locates the first occurrence in the string pointed to by s1 of the sequence of bytes (excluding the terminating null byte) in the string pointed to by s2.
Upon successful completion, strstr() returns a pointer to the located string or a null pointer if the string is not found.
If s2 points to a string with zero length, the function returns s1.
No errors are defined.
Derived from the ANSI C standard.