NAME
    mergecap - Merges two capture files into one

SYNOPSYS
    mergecap [ -hva ] [ -s snaplen ] [ -F file format ] [ -T encapsula-
    tion type ] -w outfile infile ...

DESCRIPTION
    Mergecap is a program that combines multiple saved capture files into a
    single output file specified by the -w argument.  Mergecap knows how to
    read libpcap capture files, including those of tcpdump, Ethereal, and
    other tools that write captures in that format. In addition, Mergecap
    can read capture files from snoop and atmsnoop, Shomiti/Finisar Sur-
    veyor, Novell LANalyzer, Network General/Network Associates DOS-based
    Sniffer (compressed or uncompressed), Microsoft Network Monitor, AIX's
    iptrace, Cinco Networks NetXRay, Network Associates Windows-based Snif-
    fer, AG Group/WildPackets EtherPeek/TokenPeek/AiroPeek, RADCOM's
    WAN/LAN analyzer, Lucent/Ascend router debug output, HP-UX's nettl, the
    dump output from Toshiba's ISDN routers, the output from i4btrace from
    the ISDN4BSD project, the output in IPLog format from the Cisco Secure
    Intrusion Detection System, pppd logs (pppdump format), the output from
    VMS's TCPIPtrace utility, the text output from the DBS Etherwatch VMS
    utility, traffic capture files from Visual Networks' Visual UpTime, and
    the output from CoSine L2 debug.  There is no need to tell Mergecap
    what type of file you are reading; it will determine the file type by
    itself. Mergecap is also capable of reading any of these file formats
    if they are compressed using gzip. Mergecap recognizes this directly
    from the file; the '.gz' extension is not required for this purpose.

    By default, it writes the capture file in libpcap format, and writes
    all of the packets in both input capture files to the output file. The
    -F flag can be used to specify the format in which to write the capture
    file; it can write the file in libpcap format (standard libpcap format,
    a modified format used by some patched versions of libpcap, the format
    used by Red Hat Linux 6.1, or the format used by SuSE Linux 6.3), snoop
    format, uncompressed Sniffer format, Microsoft Network Monitor 1.x for-
    mat, the format used by Windows-based versions of the Sniffer software,
    and the format used by Visual Networks' software.

    Packets from the input files are merged in chronological order based on
    each frame's timestamp, unless the -a flag is specified.  Mergecap
    assumes that frames within a single capture file are already stored in
    chronological order. When the -a flag is specified, packets are copied
    directly from each input file to the output file, independent of each
    frame's timestamp.

    If the -s flag is used to specify a snapshot length, frames in the
    input file with more captured data than the specified snapshot length
    will have only the amount of data specified by the snapshot length
    written to the output file. This may be useful if the program that is
    to read the output file cannot handle packets larger than a certain
    size (for example, the versions of snoop in Solaris 2.5.1 and Solaris
    2.6 appear to reject Ethernet frames larger than the standard Ethernet
    MTU, making them incapable of handling gigabit Ethernet captures if
    jumbo frames were used).

    The output file frame encapsulation type is set to the type of the
    input files, if all input files have the same type. If not all of the
    input files have the same frame encapsulation type, the output file
    type is set to WTAP_ENCAP_PER_PACKET. Note that some capture file for-
    mats, most notably libpcap, do not currently support
    WTAP_ENCAP_PER_PACKET. This combination will cause the output file
    creation to fail.

    If the -T flag is used to specify a frame encapsulation type, the
    encapsulation type of the output capture file will be forced to the
    specified type, rather than being the type appropriate to the encapsu-
    lation type of the input capture files. Note that this merely forces
    the encapsulation type of the output file to be the specified type; the
    packet headers of the packets will not be translated from the encapsu-
    lation type of the input capture file to the specified encapsulation
    type (for example, it will not translate an Ethernet capture to an FDDI
    capture if an Ethernet capture is read and '-T fddi' is specified).

OPTIONS
    -w Sets the output filename.

    -F Sets the file format of the output capture file.

    -T Sets the packet encapsulation type of the output capture file.

    -a Causes the frame timestamps to be ignored, writing all packets from
   the first input file followed by all packets from the second input
   file. By default, when -a is not specified, the contents of the
   input files are merged in chronological order based on each frame's
   timestamp. Note: when merging, mergecap assumes that packets
   within a capture file are already in chronological order.

    -v Causes mergecap to print a number of messages while it's working.

    -s Sets the snapshot length to use when writing the data.

    -h Prints the version and options and exits.

SEE ALSO
    tcpdump(8), pcap(3), ethereal(1),editcap(1)

NOTES
    Mergecap is based heavily upon editcap by Richard Sharpe
    <sharpe@ns.aus.com> and Guy Harris <guy@alum.mit.edu>.

    Mergecap is part of the Ethereal distribution. The latest version of
    Ethereal can be found at http://www.ethereal.com.

AUTHORS
  Original Author
  -------- ------
  Scott Renfro   <scott@renfro.org>

  Contributors
  ------------