Editcap is a program that reads a saved capture file and
writes some or all of the packets in that capture file to
another capture file. Editcap knows how to read libpcap
capture files, including those of tcpdump. In addition,
Editcap can read capture files from snoop (including
Shomiti) and atmsnoop, LanAlyzer, Sniffer (compressed or
uncompressed), Microsoft NetworkMonitor, AIX's iptrace,
NetXray, SnifferPro, RADCOM's WAN/LAN analyzer,
Lucent/Ascend router debug output, HP-UX's nettl, and the
dump output from Toshiba's ISDN routers. There is no need
to tell Editcap what type of file you are reading; it will
determine the file type by itself. Editcap is also capable
of reading any of these file formats if they are compressed
using gzip. Editcap 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 the capture file 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, or the format used
by Red Hat Linux 6.1), snoop format, uncompressed Sniffer
format, Microsoft NetworkMonitor 1.x format, and the format
used by Windows-based versions of the Sniffer software.
A list of packet numbers can be specified on the command
line; the packets with those numbers will not be written to
the capture file, unless the -r flag is specified, in which
case only those packets will be written to the capture file.
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).
If the -T flag is used to specify an 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
file. 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 '-Tfddi' is specified).
OPTIONS
-F Sets the file format of the output capture file.
-T Sets the packet encapsulation type of the output capture
file.
-r Causes the packets whose packet numbers are specified on
the command line to be written to the output capture
file, and no other packets to be written to the output
capture file.
-v Causes editcap 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 ALSO
the tcpdump(8) manpage, the pcap(3) manpage, the ethereal(1)
manpage
NOTES
Editcap is part of the Ethereal distribution. The latest
version of Ethereal can be found at
http://ethereal.zing.org.
AUTHORS
Original Author
-------- ------
Richard Sharpe <sharpe@ns.aus.com>
Contributors
------------
Guy Harris <guy@alum.mit.edu>