MERGECAP(1) The Ethereal Network Analyzer MERGECAP(1)NAMEmergecap - Merges two capture files into one
SYNOPSYSmergecap [ -hva ] [ -s snaplen ] [ -F file format ]
[ -T encapsulation 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 Surveyor, 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 Sniffer, 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 format, 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
formats, 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 encapsulation 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 encapsulation 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 ALSOtcpdump(8), pcap(3), ethereal(1), editcap(1)NOTES
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 Ethereal distribution. The latest
version of Ethereal can be found at
http://www.ethereal.com.
AUTHORS
Original Author
-------- ------
Scott Renfro <scott[AT]renfro.org>
Contributors
------------
9/Mar/2003 0.9.12 MERGECAP(1)
