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| 20 | .TH PCAP_GET_REQUIRED_SELECT_TIMEOUT 3PCAP "20 January 2018" |
| 21 | .SH NAME |
| 22 | pcap_get_required_select_timeout \- get a file descriptor on which a |
| 23 | select() can be done for a live capture |
| 24 | .SH SYNOPSIS |
| 25 | .nf |
| 26 | .ft B |
| 27 | #include <pcap/pcap.h> |
| 28 | .ft |
| 29 | .LP |
| 30 | .ft B |
| 31 | struct timeval *pcap_get_required_select_timeout(pcap_t *p); |
| 32 | .ft |
| 33 | .fi |
| 34 | .SH DESCRIPTION |
| 35 | .B pcap_get_required_select_timeout() |
| 36 | returns, on UNIX, a pointer to a |
| 37 | .B struct timeval |
| 38 | containing a value that must be used as the minimum timeout in |
| 39 | .BR select() , |
| 40 | .BR poll() , |
| 41 | .BR epoll_wait() , |
| 42 | and |
| 43 | .B kevent() |
| 44 | calls if |
| 45 | .B pcap_get_selectable_fd() |
| 46 | returns \-1. |
| 47 | .PP |
| 48 | The timeout that should be used in those calls must be no larger than |
| 49 | the smallest of all timeouts returned by |
| 50 | .B pcap_get_required_select_timeout() |
| 51 | for devices from which packets will be captured. |
| 52 | .PP |
| 53 | The device for which |
| 54 | .B pcap_get_selectable_fd() |
| 55 | returned \-1 must be put in non-blocking mode with |
| 56 | .BR pcap_setnonblock() , |
| 57 | and an attempt must always be made to read packets from the device |
| 58 | when the |
| 59 | .BR select() , |
| 60 | .BR poll() , |
| 61 | .BR epoll_wait() , |
| 62 | or |
| 63 | .B kevent() |
| 64 | call returns. |
| 65 | .PP |
| 66 | Note that a device on which a read can be done without blocking may, |
| 67 | on some platforms, not have any packets to read if the packet buffer |
| 68 | timeout has expired. A call to |
| 69 | .B pcap_dispatch() |
| 70 | or |
| 71 | .B pcap_next_ex() |
| 72 | will return 0 in this case, but will not block. |
| 73 | .PP |
| 74 | .B pcap_get_required_select_timeout() |
| 75 | is not available on Windows. |
| 76 | .SH RETURN VALUE |
| 77 | A pointer to a |
| 78 | .B struct timeval |
| 79 | is returned if the timeout is required; otherwise |
| 80 | .B NULL |
| 81 | is returned. |
| 82 | .SH SEE ALSO |
| 83 | pcap(3PCAP), pcap_get_selectable_fd(3PCAP), select(2), poll(2), |
| 84 | epoll_wait(2), kqueue(2) |