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  22 .TH PCAP_NEXT_EX 3PCAP "4 April 2008"
  23 .SH NAME
  24 pcap_next_ex, pcap_next \- read the next packet from a pcap_t
  25 .SH SYNOPSIS
  26 .nf
  27 .ft B
  28 #include <pcap.h>
  29 .ft
  30 .LP
  31 .ft B
  32 int pcap_next_ex(pcap_t *p, struct pcap_pkthdr **pkt_header,
  33 .ti +8
  34 const u_char **pkt_data);
  35 const u_char *pcap_next(pcap_t *p, struct pcap_pkthdr *h);
  36 .ft
  37 .fi
  38 .SH DESCRIPTION
  39 .B pcap_next_ex()
  40 reads the next packet and returns a success/failure indication.
  41 If the packet was read without problems, the pointer pointed to by the
  42 .I pkt_header
  43 argument is set to point to the
  44 .I pcap_pkthdr
  45 struct for the packet, and the
  46 pointer pointed to by the
  47 .I pkt_data
  48 argument is set to point to the data in the packet.
  49 .PP
  50 .B pcap_next()
  51 reads the next packet (by calling
  52 .B pcap_dispatch()
  53 with a
  54 .I cnt
  55 of 1) and returns a
  56 .I u_char
  57 pointer to the data in that packet.
  58 The
  59 .I pcap_pkthdr
  60 structure pointed to by
  61 .I h
  62 is filled in with the appropriate values for the packet.
  63 .SH RETURN VALUE
  64 .B pcap_next_ex()
  65 returns 1 if the packet was read without problems, 0
  66 if packets are being read from a live capture, and the timeout expired,
  67 \-1 if an error occurred while reading the packet, and \-2 if
  68 packets are being read from a ``savefile'', and there are no more
  69 packets to read from the savefile.
  70 If \-1 is returned,
  71 .B pcap_geterr()
  72 or
  73 .B pcap_perror()
  74 may be called with
  75 .I p
  76 as an argument to fetch or display the error text.
  77 .PP
  78 .B pcap_next()
  79 returns a pointer to the packet data on success, and returns
  80 .B NULL
  81 if an error occured, or if no packets were read from a live
  82 capture (if, for example, they were discarded because they didn't pass
  83 the packet filter, or if, on platforms that support a read timeout that
  84 starts before any packets arrive, the timeout expires before any packets
  85 arrive, or if the file descriptor for the capture device is in
  86 non-blocking mode and no packets were available to be read), or if no
  87 more packets are available in a ``savefile.''  Unfortunately, there is
  88 no way to determine whether an error occured or not.
  89 .SH SEE ALSO
  90 pcap_geterr(3PCAP), pcap_dispatch(3PCAP)