синхронное мультиплексирование ввода / вывода (synchronous I/O multiplexing)
Ошибки (Error)
Under the following conditions, pselect() and select() shall fail
and set errno to:
EBADF One or more of the file descriptor sets specified a file
descriptor that is not a valid open file descriptor.
EINTR The function was interrupted while blocked waiting for any
of the selected descriptors to become ready and before the
timeout interval expired.
If SA_RESTART has been set for the interrupting
signal, it is implementation-defined whether the
function restarts or returns with [EINTR].
EINVAL An invalid timeout interval was specified.
EINVAL The nfds argument is less than 0 or greater than
FD_SETSIZE.
EINVAL One of the specified file descriptors refers to a STREAM
or multiplexer that is linked (directly or indirectly)
downstream from a multiplexer.
The following sections are informative.
