Section: The Wireshark Network Analyzer (1)
Return to Main Contents
editcap - Edit and/or translate the format of capture files
[ -c <packets per file> ]
[ -C <choplen> ]
[ -d ]
[ -E <error probability> ]
[ -F <file format> ]
[ -A <start time> ]
[ -B <stop time> ]
[ -h ]
[ -r ]
[ -s <snaplen> ]
[ -t <time adjustment> ]
[ -T <encapsulation type> ]
[ -v ]
[ packet#[-packet#] ... ]
Editcap is a program that reads some or all of the captured packets from the
infile, optionally converts them in various ways and writes the
resulting packets to the capture outfile (or outfiles).
By default, it reads all packets from the infile and writes them to the
outfile in libpcap file format.
A list of packet numbers can be specified on the command line; ranges of
packet numbers can be specified as start-end, referring to all packets
from start to end.
The selected packets with those numbers will not be written to the
If the -r flag is specified, the whole packet selection is reversed;
in that case only the selected packets will be written to the capture file.
Editcap is able to detect, read and write the same capture files that
are supported by Wireshark.
The input file doesn'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 Editcap handles this.
Editcap 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, editcap -F provides a list of the available output formats.
- -c <packets per file>
Sets the maximum number of packets per output file. Each output file will
be created with a suffix -nnnnn, starting with 00000. If the specified
number of packets are written to the output file, the next output file is
opened. The default is to use a single output file.
- -C <choplen>
Sets the chop length to use when writing the packet data.
Each packet is chopped at the packet end by a few <choplen> bytes of data.
This is useful in the rare case that the conversion between two file
formats leaves some random bytes at the end of each packet.
Attempts to remove duplicate packets. The length and MD5 sum of the
current packet are compared to the previous four packets. If a match
is found, the packet is skipped.
- -E <error probability>
Sets the probabilty that bytes in the output file are randomly changed.
Editcap uses that probability (between 0.0 and 1.0 inclusive)
to apply errors to each data byte in the file. For instance, a
probability of 0.02 means that each byte has a 2% chance of having an error.
This option is meant to be used for fuzz-testing protocol dissectors.
- -F <file format>
Sets the file format of the output capture file.
Editcap can write the file in several formats, editcap -F
provides a list of the available output formats. The default
is the libpcap format.
- -A <start time>
Saves only the packets whose timestamp is on or after start time.
The time is given in the following format YYYY-MM-DD HH:MM:SS
- -B <stop time>
Saves only the packets whose timestamp is on or before stop time.
The time is given in the following format YYYY-MM-DD HH:MM:SS
Prints the version and options and exits.
Reverse the packet selection.
Causes the packets whose packet numbers are specified on the command
line to be written to the output capture file, instead of discarding them.
- -s <snaplen>
Sets the snapshot length to use when writing the data.
If the -s flag is used to specify a snapshot length, packets 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 packets larger than the standard Ethernet MTU,
making them incapable of handling gigabit Ethernet captures if jumbo
packets were used).
- -t <time adjustment>
Sets the time adjustment to use on selected packets.
If the -t flag is used to specify a time adjustment, the specified
adjustment will be applied to all selected packets in the capture file.
The adjustment is specified as [-]seconds[.fractional seconds].
For example, -t 3600 advances the timestamp on selected packets by one
hour while -t -0.5 reduces the timestamp on selected packets by
This feature is useful when synchronizing dumps
collected on different machines where the time difference between the
two machines is known or can be estimated.
- -T <encapsulation type>
Sets the packet encapsulation type of the output capture file.
If the -T flag is used to specify an encapsulation type, the
encapsulation type of the output capture file will be forced to the
editcap -T provides a list of the available types. The default
type is the one appropriate to the encapsulation type of the input
Note: 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). If you need to remove/add headers from/to a
packet, you will need od(1)/text2pcap(1).
Causes editcap to print verbose messages while it's working.
To see more detailed description of the options use:
To shrink the capture file by truncating the packets at 64 bytes and writing it as Sun snoop file use:
editcap -s 64 -F snoop capture.pcap shortcapture.snoop
To delete packet 1000 from the capture file use:
editcap capture.pcap sans1000.pcap 1000
To limit a capture file to packets from number 200 to 750 (inclusive) use:
editcap -r capture.pcap small.pcap 200-750
To get all packets from number 1-500 (inclusive) use:
editcap -r capture.pcap 500.pcap 1-500
editcap capture.pcap 500.pcap 501-9999999
To filter out packets 10 to 20 and 30 to 40 into a new file use:
editcap capture.pcap selection.pcap 10-20 30-40
To introduce 5% random errors in a capture file use:
editcap -E 0.05 capture.pcap capture_error.pcap
tcpdump(8), pcap(3), wireshark(1), tshark(1), mergecap(1), dumpcap(1),
capinfos(1), text2pcap(1), od(1)
Editcap is part of the Wireshark distribution. The latest version
of Wireshark can be found at <http://www.wireshark.org>.
HTML versions of the Wireshark project man pages are available at:
Richard Sharpe <sharpe[AT]ns.aus.com>
Guy Harris <guy[AT]alum.mit.edu>
Ulf Lamping <ulf.lamping[AT]web.de>
- SEE ALSO
linux.jgfs.net manual pages