3.8. strncat

char *strncat( char * restrict s1, const char * restrict s2, size_t n);

strncat concatenates at most n characters of string s2 to string s1, terminates s1 with '\0', and returns s1.

Examples:

        strcpy( str, "abc");
        strncat( str, "def", 2);

Now str contains "abcde".

        strcpy( str, "abc");
        strncat( str, "def", 9);

Now str contains "abcdef".