Basic I/O.
Openssl code: crypto.hbio_lib.c
val gets : Pervasives.in_channel ‑> Bytes.t ‑> int ‑> int ‑> intgets ic buf pos max gets a line from ic and puts it at pos in buf.
Number of bytes read is returned.
If 0 bytes are read, then ic is at end of file.
Line length is limited to max bytes if no newline is found.
The newline is included in the line if a newline is found.