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 frames 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. The default is to use the file format of the first input file.|
|-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:
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 its working.|
|-V||Print the version and exit.|
|-w <outfile>|-||Sets the output filename. If the name is -, stdout will be used. This setting is mandatory.|
To merge two capture files together, 100 seconds apart use:
capinfos -aeS a.pcap b.pcap
(Lets 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 tcpdump(8)
Mergecap is based heavily upon editcap by Richard Sharpe <sharpe[AT]ns.aus.com> and Guy Harris <guy[AT]alum.mit.edu>.
Mergecap is part of the Wireshark distribution. The latest version of Wireshark can be found at <https://www.wireshark.org>.
HTML versions of the Wireshark project man pages are available at: <https://www.wireshark.org/docs/man-pages>.
Original Author -------- ------ Scott Renfro <scott[AT]renfro.org> Contributors ------------ Bill Guyton <guyton[AT]bguyton.com>