Returns a portion of a the string **_s_**, specified by the **offset** and **length** parameters. The string porttion is copied into the string **dest**, up to a limit of **max_len** characters. If there is not enough room, **NULL** is returned.
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Returns a portion of a the string **_s_**, specified by the **_from_** and **_to_** parameters. The string porttion is copied into the string **_dest_**, up to a limit of **_max_len_** characters. If there is not enough room, **NULL** is returned.