1PCAP_GET_REQUIRED_SELECT_TIMEOUT(3PCAP)PCAP_GET_REQUIRED_SELECT_TIMEOUT(3PCAP)
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NAME

6       pcap_get_required_select_timeout  -  get  a  file descriptor on which a
7       select() can be done for a live capture
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SYNOPSIS

10       #include <pcap/pcap.h>
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12       struct timeval *pcap_get_required_select_timeout(pcap_t *p);
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DESCRIPTION

15       pcap_get_required_select_timeout() returns, on UNIX,  a  pointer  to  a
16       struct  timeval  containing  a  value  that must be used as the minimum
17       timeout in select(2), poll(2), epoll_wait(2),  and  kevent()  calls  if
18       pcap_get_selectable_fd(3PCAP) returns PCAP_ERROR.
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20       The  timeout  that should be used in those calls must be no larger than
21       the      smallest      of      all      timeouts      returned       by
22       pcap_get_required_select_timeout()  for devices from which packets will
23       be captured.
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25       The device for which pcap_get_selectable_fd() returned PCAP_ERROR  must
26       be  put  in  non-blocking  mode  with  pcap_setnonblock(3PCAP),  and an
27       attempt must always be made to read packets from the  device  when  the
28       select(), poll(), epoll_wait(), or kevent() call returns.
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30       Note that a device on which a read can be done without blocking may, on
31       some platforms, not have any packets to read if the packet buffer time‐
32       out has expired.  A call to pcap_dispatch(3PCAP) or pcap_next_ex(3PCAP)
33       will return 0 in this case, but will not block.
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35       pcap_get_required_select_timeout() is not available on Windows.
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RETURN VALUE

38       A pointer to a struct timeval is returned if the timeout  is  required;
39       otherwise NULL is returned.
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BACKWARD COMPATIBILITY

42       This  function  became available in libpcap release 1.9.0.  In previous
43       releases, select(), poll(), epoll_wait(), and kevent() cannot  be  used
44       on any capture source for which pcap_get_selectable_fd returns -1.
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SEE ALSO

47       pcap(3PCAP),    pcap_get_selectable_fd(3PCAP),    select(2),   poll(2),
48       epoll_wait(2), kqueue(2)
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