Os.FdFile descriptors operations.
unix_buffer_size is the value of the OCaml runtime system buffer size for I/O operations.
Available in 5.4 as Sys.io_buffer_size.
close_noerr fd uses Unix.close on fd, retries on EINTR and silently catches any error it may raise. Typically used with Fun.protect.
copy ~buf src ~dst reads src and writes it to dst using buf as a buffer; if unspecified a buffer of length unix_buffer_size is created for the call. Raise Unix.Unix_error if that happens
to_string fd reads fd to a string. Raises Unix.Unix_error in case of error.