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pcap_get_required_select_timeout - get a file descriptor on which a
select() can be done for a live capture
struct timeval *pcap_get_required_select_timeout(pcap_t *p);
pcap_get_required_select_timeout() returns, on UNIX, a pointer to a
struct timeval containing a value that must be used as the minimum
timeout in select(2), poll(2), epoll_wait(2), and kevent() calls if
pcap_get_selectable_fd(3) returns PCAP_ERROR.
The timeout that should be used in those calls must be no larger than
the smallest of all timeouts returned by
pcap_get_required_select_timeout() for devices from which packets will
The device for which pcap_get_selectable_fd() returned PCAP_ERROR must
be put in non-blocking mode with pcap_setnonblock(3), and an attempt
must always be made to read packets from the device when the select(),
poll(), epoll_wait(), or kevent() call returns.
Note that a device on which a read can be done without blocking may, on
some platforms, not have any packets to read if the packet buffer time-
out has expired. A call to pcap_dispatch(3) or pcap_next_ex(3) will
return 0 in this case, but will not block.
pcap_get_required_select_timeout() is not available on Windows.
A pointer to a struct timeval is returned if the timeout is required;
otherwise NULL is returned.
This function became available in libpcap release 1.9.0. In previous
releases, select(), poll(), epoll_wait(), and kevent() cannot be used
on any capture source for which pcap_get_selectable_fd returns -1.
pcap(3), pcap_get_selectable_fd(3), select(2), poll(2), epoll_wait(2),
25 July 20PCAP_GET_REQUIRED_SELECT_TIMEOUT(3)