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editcap [ -c <packets per file> ] [ -C <choplen> ] [ -E <error probability> ] [ -F <file format> ] [ -A <start time> ] [ -B <stop time> ] [ -h ] [ -r ] [ -s <snaplen> ] [ -t <time adjustment> ] [ -T <encapsulation type> ] [ -v ] infile outfile [ packet#[-packet#] ... ]
Editcap is a filter 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 capture file. 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 Ethereal. The input file doesn't need a specific filename extension, the file format and an optional gzip compression will be automatically detected. The capture file format section of ethereal(1) or http://www.ethereal.com/docs/man-pages/ethereal.1.html provides a detailed description.
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.
This is useful in the rare case that the conversion between two file formats leaves some random bytes at the end of each packet.
This option is meant to be used for fuzz-testing protocol dissectors.
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).
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.
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).
To see more detailed description of the options use:
editcap -h
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
or
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
