Provided by: wireshark-common_2.6.10-1~ubuntu16.04.0_amd64 bug


       mergecap - Merges two or more capture files into one


       mergecap [ -a ] [ -F <file format> ] [ -h ] [ -I <IDB merge mode> ] [ -s <snaplen> ]
       [ -v ] [ -V ] -w <outfile>|- <infile> [<infile> ...]


       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 pcap and pcapng capture files,
       including those of tcpdump, Wireshark and other tools that write captures in those

       By default, Mergecap writes the capture file in pcapng format, and writes all of the
       packets from the input capture files to the output file.

       Mergecap is able to detect, read and write the same capture files that are supported by
       Wireshark.  The input files don't need a specific filename extension; the file format and
       an optional gzip compression will be automatically detected.  Near the beginning of the
       DESCRIPTION section of wireshark(1) or
       <> is a detailed description of the
       way Wireshark handles this, which is the same way Mergecap handles this.

       Mergecap can write the file in several output formats.  The -F flag can be used to specify
       the format in which to write the capture file, mergecap -F provides a list of the
       available output formats.

       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.

       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 formats, most notably pcap, do not currently support WTAP_ENCAP_PER_PACKET.
       This combination will cause the output file creation to fail.


       -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.

       -F  <file format>
           Sets the file format of the output capture file. Mergecap can write the file in
           several formats; mergecap -F provides a list of the available output formats.  By
           default this is the pcapng format.

       -h  Prints the version and options and exits.

       -I  <IDB merge mode>
           Sets the Interface Description Block (IDB) merge mode to use during merging.  mergecap
           -I provides a list of the available IDB merge modes.

           Every input file has one or more IDBs, which describe the interface(s) the capture was
           performed on originally. This includes encapsulation type, interface name, etc. When
           mergecap merges multiple input files, it has to merge these IDBs somehow for the new
           merged output file. This flag controls how that is accomplished. The currently
           available modes are:

            * 'B<none>': no merging of IDBs is performed, and instead all IDBs are
                         copied to the merged output file.
            * 'B<all>':  IDBs are merged only if all input files have the same number
                         of IDBs, and each IDB matches their respective entry in the
                         other files. This is the default mode.
            * 'B<any>':  Any and all duplicate IDBs are merged into one IDB, regardless
                         of what file they are in.

           Note that an IDB is only considered a matching duplicate if it has the same
           encapsulation type, name, speed, time precision, comments, description, etc.

       -s  <snaplen>
           Sets the snapshot length to use when writing the data.  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).

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

       -V  Print the version and exit.

       -w  <outfile>|-
           Sets the output filename. If the name is '-', stdout will be used.  This setting is


       To merge two capture files together, 100 seconds apart use:

           capinfos -aeS a.pcap b.pcap

       (Let's suppose a.pcap starts at 1009932757 and b.pcap ends at 873660281. 1009932757 -
       873660281 - 100 = 136272376 seconds.)

           editcap -t 136272376 b.pcap b-shifted.pcap
           mergecap -w compare.pcap a.pcap b-shifted.pcap


       pcap(3), wireshark(1), tshark(1), dumpcap(1), editcap(1), text2pcap(1), pcap-filter(7) or


       Mergecap is based heavily upon editcap by Richard Sharpe <sharpe[AT]> and Guy
       Harris <guy[AT]>.

       Mergecap is part of the Wireshark distribution.  The latest version of Wireshark can be
       found at <>.

       HTML versions of the Wireshark project man pages are available at:


         Original Author
         -------- ------
         Scott Renfro             <scott[AT]>

         Bill Guyton              <guyton[AT]>