NAME

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

SYNOPSIS

       #include <pcap/pcap.h>

       struct timeval *pcap_get_required_select_timeout(pcap_t *p);

DESCRIPTION

       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(3PCAP) 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 be captured.

       The device for which pcap_get_selectable_fd() returned PCAP_ERROR  must  be  put  in  non-
       blocking  mode  with  pcap_setnonblock(3PCAP),  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 timeout has expired.  A call to
       pcap_dispatch(3PCAP) or pcap_next_ex(3PCAP) will return 0  in  this  case,  but  will  not
       block.

       pcap_get_required_select_timeout() is not available on Windows.

RETURN VALUE

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

BACKWARD COMPATIBILITY

       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.

SEE ALSO

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

                                           25 July 2018   PCAP_GET_REQUIRED_SELECT_TIMEOUT(3PCAP)