=head1 NAME

editcap - Edit and/or translate the format of capture files

=head1 SYNOPSYS

B<editcap>
S<[ B<-F> file format ]>
S<[ B<-T> encapsulation type ]>
S<[ B<-r> ]>
S<[ B<-v> ]>
S<[ B<-s> snaplen ]>
S<[ B<-t> time adjustment ]>
S<[ B<-h> ]>
I<infile>
I<outfile>
S<[ I<record#> ... ]>

=head1 DESCRIPTION

B<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. 
B<Editcap> knows how to read B<libpcap> capture files, including those
of B<tcpdump>, B<Ethereal>, and other tools that write captures in that
format.  In addition, B<Editcap> can read capture files from B<snoop>
and B<atmsnoop>, Shomiti/Finisar B<Surveyor>, Novell B<LANalyzer>,
Network General/Network Associates DOS-based B<Sniffer> (compressed or
uncompressed), Microsoft B<Network Monitor>, AIX's B<iptrace>, Cinco
Networks B<NetXRay>, Network Associates Windows-based B<Sniffer>, AG
Group/WildPackets B<EtherPeek>/B<TokenPeek>/B<AiroPeek>, B<RADCOM>'s
WAN/LAN analyzer, B<Lucent/Ascend> router debug output, HP-UX's
B<nettl>, the dump output from B<Toshiba's> ISDN routers, the output
from B<i4btrace> from the ISDN4BSD project, the output in B<IPLog>
format from the Cisco Secure Intrusion Detection System, B<pppd logs>
(pppdump format), the output from VMS's B<TCPIPtrace> utility, the text
output from the B<DBS Etherwatch> VMS utility, and traffic capture files
from Visual Networks' Visual UpTime.  There is no need to tell
B<Editcap> what type of file you are reading; it will determine the file
type by itself.  B<Editcap> is also capable of reading any of these file
formats if they are compressed using gzip.  B<Editcap> recognizes this
directly from the file; the '.gz' extension is not required for this
purpose.

By default, it writes the capture file in B<libpcap> format, and writes
all of the packets in the capture file to the output file.  The B<-F>
flag can be used to specify the format in which to write the capture
file; it can write the file in B<libpcap> format (standard B<libpcap>
format, a modified format used by some patched versions of B<libpcap>,
the format used by Red Hat Linux 6.1, or the format used by SuSE Linux
6.3), B<snoop> format, uncompressed B<Sniffer> format, Microsoft
B<Network Monitor> 1.x format, the format used by Windows-based versions
of the B<Sniffer> software, and the format used by Visual Networks'
software.

A list of packet numbers can be specified on the command line; the
packets with those numbers will I<not> be written to the capture file,
unless the B<-r> flag is specified, in which case I<only> those packets
will be written to the capture file.  Ranges of packet numbers can be
specified as I<start>-I<end>, referring to all packets from I<start> to
I<end> (removing them all if B<-r> isn't specified, including them all
if B<-r> is specified).

If the B<-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 B<-t> flag is used to specify a time adjustment, the specified
adjustment will be applied to all selected frames in the capture file.
The adjustment is specified as [-]I<seconds>[I<.fractional seconds>].
For example, B<-t> 3600 advances the timestamp on selected frames by one
hour while B<-t> -0.5 reduces the timestamp on selected frames by
one-half second.  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.

If the B<-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 'B<-T
fddi>' is specified).

=head1 OPTIONS

=over 4

=item -F

Sets the file format of the output capture file.

=item -T

Sets the packet encapsulation type of the output capture file.

=item -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.

=item -v

Causes B<editcap> to print a number of messages while it's working.

=item -s

Sets the snapshot length to use when writing the data.

=item -t

Sets the time adjustment to use on selected frames.

=item -h

Prints the version and options and exits.

=head1 SEE ALSO

I<tcpdump(8)>, I<pcap(3)>, I<ethereal(1)>, I<mergecap(1)>

=head1 NOTES

B<Editcap> is part of the B<Ethereal> distribution.  The latest version
of B<Ethereal> can be found at B<http://www.ethereal.com>.

=head1 AUTHORS

  Original Author
  -------- ------
  Richard Sharpe           <sharpe@ns.aus.com>


  Contributors
  ------------
  Guy Harris               <guy@alum.mit.edu>