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DUMPCAP(1)		The Wireshark Network Analyzer		    DUMPCAP(1)

NAME
       dumpcap - Dump network traffic

SYNOPSIS
       dumpcap [ -a <capture autostop condition> ] ...
       [ -b <capture ring buffer option>] ...  [ -B <capture buffer size> ]
       [ -c <capture packet count> ] [ -C <byte limit> ] [ -d ] [ -D ]
       [ -f <capture filter> ] [ -g ] [ -h ]
       [ -i <capture interface>|rpcap://<host>/<capture interface>|TCP@<host>:<port>|- ]
       [ -I ] [ -L ] [ -M ] [ -n ] [ -N <packet limit> ] [ -p ] [ -P ] [ -q ]
       [ -s <capture snaplen> ] [ -S ] [ -t ] [ -v ] [ -w <outfile> ]
       [ -y <capture link type> ]

DESCRIPTION
       Dumpcap is a network traffic dump tool.	It lets you capture packet
       data from a live network and write the packets to a file.  Dumpcap's
       default capture file format is pcap-ng format.  When the -P option is
       specified, the output file is written in the pcap format.

       Without any options set it will use the libpcap/WinPcap library to
       capture traffic from the first available network interface and writes
       the received raw packet data, along with the packets' time stamps into
       a pcap file.

       If the -w option is not specified, Dumpcap writes to a newly created
       pcap file with a randomly chosen name.  If the -w option is specified,
       Dumpcap writes to the file specified by that option.

       Packet capturing is performed with the pcap library.  The capture
       filter syntax follows the rules of the pcap library.

OPTIONS
       -a  <capture autostop condition>
	   Specify a criterion that specifies when Dumpcap is to stop writing
	   to a capture file.  The criterion is of the form test:value, where
	   test is one of:

	   duration:value Stop writing to a capture file after value seconds
	   have elapsed.

	   filesize:value Stop writing to a capture file after it reaches a
	   size of value KiB. If this option is used together with the -b
	   option, dumpcap will stop writing to the current capture file and
	   switch to the next one if filesize is reached.  Note that the
	   filesize is limited to a maximum value of 2 GiB.

	   files:value Stop writing to capture files after value number of
	   files were written.

       -b  <capture ring buffer option>
	   Cause Dumpcap to run in "multiple files" mode.  In "multiple files"
	   mode, Dumpcap will write to several capture files. When the first
	   capture file fills up, Dumpcap will switch writing to the next file
	   and so on.

	   The created filenames are based on the filename given with the -w
	   option, the number of the file and on the creation date and time,
	   e.g. outfile_00001_20050604120117.pcap,
	   outfile_00002_20050604120523.pcap, ...

	   With the files option it's also possible to form a "ring buffer".
	   This will fill up new files until the number of files specified, at
	   which point Dumpcap will discard the data in the first file and
	   start writing to that file and so on. If the files option is not
	   set, new files filled up until one of the capture stop conditions
	   match (or until the disk is full).

	   The criterion is of the form key:value, where key is one of:

	   duration:value switch to the next file after value seconds have
	   elapsed, even if the current file is not completely filled up.

	   filesize:value switch to the next file after it reaches a size of
	   value KiB.  Note that the filesize is limited to a maximum value of
	   2 GiB.

	   files:value begin again with the first file after value number of
	   files were written (form a ring buffer).  This value must be less
	   than 100000.	 Caution should be used when using large numbers of
	   files: some filesystems do not handle many files in a single
	   directory well.  The files criterion requires either duration or
	   filesize to be specified to control when to go to the next file.
	   It should be noted that each -b parameter takes exactly one
	   criterion; to specify two criterion, each must be preceded by the
	   -b option.

	   Example: -b filesize:1024 -b files:5 results in a ring buffer of
	   five files of size one megabyte.

       -B  <capture buffer size>
	   Set capture buffer size (in MB, default is 2MB).  This is used by
	   the the capture driver to buffer packet data until that data can be
	   written to disk.  If you encounter packet drops while capturing,
	   try to increase this size.  Note that, while Dumpcap attempts to
	   set the buffer size to 2MB by default, and can be told to set it to
	   a larger value, the system or interface on which you're capturing
	   might silently limit the capture buffer size to a lower value or
	   raise it to a higher value.

	   This is available on UNIX systems with libpcap 1.0.0 or later and
	   on Windows.	It is not available on UNIX systems with earlier
	   versions of libpcap.

	   This option can occur multiple times. If used before the first
	   occurrence of the -i option, it sets the default capture buffer
	   size.  If used after an -i option, it sets the capture buffer size
	   for the interface specified by the last -i option occurring before
	   this option. If the capture buffer size is not set specifically,
	   the default capture buffer size is used if provided.

       -c  <capture packet count>
	   Set the maximum number of packets to read when capturing live data.

       -C  <byte limit>
	   Limit the amount of memory in bytes used for storing captured
	   packets in memory while processing it.  If used in combination with
	   the -N option, both limits will apply.  Setting this limit will
	   enable the usage of the separate thread per interface.

       -d  Dump the code generated for the capture filter in a human-readable
	   form, and exit.

       -D  Print a list of the interfaces on which Dumpcap can capture, and
	   exit.  For each network interface, a number and an interface name,
	   possibly followed by a text description of the interface, is
	   printed.  The interface name or the number can be supplied to the
	   -i option to specify an interface on which to capture.

	   This can be useful on systems that don't have a command to list
	   them (e.g., Windows systems, or UNIX systems lacking ifconfig -a);
	   the number can be useful on Windows 2000 and later systems, where
	   the interface name is a somewhat complex string.

	   Note that "can capture" means that Dumpcap was able to open that
	   device to do a live capture. Depending on your system you may need
	   to run dumpcap from an account with special privileges (for
	   example, as root) to be able to capture network traffic.  If
	   "dumpcap -D" is not run from such an account, it will not list any
	   interfaces.

       -f  <capture filter>
	   Set the capture filter expression.

	   The entire filter expression must be specified as a single argument
	   (which means that if it contains spaces, it must be quoted).

	   This option can occur multiple times. If used before the first
	   occurrence of the -i option, it sets the default capture filter
	   expression.	If used after an -i option, it sets the capture filter
	   expression for the interface specified by the last -i option
	   occurring before this option. If the capture filter expression is
	   not set specifically, the default capture filter expression is used
	   if provided.

       -g  This option causes the output file(s) to be created with group-read
	   permission (meaning that the output file(s) can be read by other
	   members of the calling user's group).

       -h  Print the version and options and exits.

       -i  <capture interface>|rpcap://<host>/<capture
       interface>|TCP@<host>:<port>|-
	   Set the name of the network interface or pipe to use for live
	   packet capture.

	   Network interface names should match one of the names listed in
	   "dumpcap -D" (described above); a number, as reported by "dumpcap
	   -D", can also be used.  If you're using UNIX, "netstat -i" or
	   "ifconfig -a" might also work to list interface names, although not
	   all versions of UNIX support the -a option to ifconfig.

	   If no interface is specified, Dumpcap searches the list of
	   interfaces, choosing the first non-loopback interface if there are
	   any non-loopback interfaces, and choosing the first loopback
	   interface if there are no non-loopback interfaces. If there are no
	   interfaces at all, Dumpcap reports an error and doesn't start the
	   capture.

	   Pipe names should be either the name of a FIFO (named pipe) or
	   ``-'' to read data from the standard input.	Data read from pipes
	   must be in standard pcap format.

	   This option can occur multiple times. When capturing from multiple
	   interfaces, the capture file will be saved in pcap-ng format.

	   Note: the Win32 version of Dumpcap doesn't support capturing from
	   pipes or stdin!

       -I  Put the interface in "monitor mode"; this is supported only on IEEE
	   802.11 Wi-Fi interfaces, and supported only on some operating
	   systems.

	   Note that in monitor mode the adapter might disassociate from the
	   network with which it's associated, so that you will not be able to
	   use any wireless networks with that adapter.	 This could prevent
	   accessing files on a network server, or resolving host names or
	   network addresses, if you are capturing in monitor mode and are not
	   connected to another network with another adapter.

	   This option can occur multiple times. If used before the first
	   occurrence of the -i option, it enables the monitor mode for all
	   interfaces.	If used after an -i option, it enables the monitor
	   mode for the interface specified by the last -i option occurring
	   before this option.

       -L  List the data link types supported by the interface and exit. The
	   reported link types can be used for the -y option.

       -M  When used with -D, -L or -S, print machine-readable output.	The
	   machine-readable output is intended to be read by Wireshark and
	   TShark; its format is subject to change from release to release.

       -n  Save files as pcap-ng. This is the default.

       -N  <packet limit>
	   Limit the number of packets used for storing captured packets in
	   memory while processing it.	If used in combination with the -C
	   option, both limits will apply.  Setting this limit will enable the
	   usage of the separate thread per interface.

       -p  Don't put the interface into promiscuous mode.  Note that the
	   interface might be in promiscuous mode for some other reason;
	   hence, -p cannot be used to ensure that the only traffic that is
	   captured is traffic sent to or from the machine on which Dumpcap is
	   running, broadcast traffic, and multicast traffic to addresses
	   received by that machine.

	   This option can occur multiple times. If used before the first
	   occurrence of the -i option, no interface will be put into the
	   promiscuous mode.  If used after an -i option, the interface
	   specified by the last -i option occurring before this option will
	   not be put into the promiscuous mode.

       -P  Save files as pcap instead of the default pcap-ng. In situations
	   that require pcap-ng, such as capturing from multiple interfaces,
	   this option will be overridden.

       -q  When capturing packets, don't display the continuous count of
	   packets captured that is normally shown when saving a capture to a
	   file; instead, just display, at the end of the capture, a count of
	   packets captured.  On systems that support the SIGINFO signal, such
	   as various BSDs, you can cause the current count to be displayed by
	   typing your "status" character (typically control-T, although it
	   might be set to "disabled" by default on at least some BSDs, so
	   you'd have to explicitly set it to use it).

       -s  <capture snaplen>
	   Set the default snapshot length to use when capturing live data.
	   No more than snaplen bytes of each network packet will be read into
	   memory, or saved to disk.  A value of 0 specifies a snapshot length
	   of 65535, so that the full packet is captured; this is the default.

	   This option can occur multiple times. If used before the first
	   occurrence of the -i option, it sets the default snapshot length.
	   If used after an -i option, it sets the snapshot length for the
	   interface specified by the last -i option occurring before this
	   option. If the snapshot length is not set specifically, the default
	   snapshot length is used if provided.

       -S  Print statistics for each interface once every second.

       -t  Use a separate thread per interface.

       -v  Print the version and exit.

       -w  <outfile>
	   Write raw packet data to outfile.

	   NOTE: The usage of "-" for stdout is not allowed here!

       -y  <capture link type>
	   Set the data link type to use while capturing packets.  The values
	   reported by -L are the values that can be used.

	   This option can occur multiple times. If used before the first
	   occurrence of the -i option, it sets the default capture link type.
	   If used after an -i option, it sets the capture link type for the
	   interface specified by the last -i option occurring before this
	   option. If the capture link type is not set specifically, the
	   default capture link type is used if provided.

CAPTURE FILTER SYNTAX
       See the manual page of pcap-filter(7) or, if that doesn't exist,
       tcpdump(8), or, if that doesn't exist,
       <http://wiki.wireshark.org/CaptureFilters>.

SEE ALSO
       wireshark(1), tshark(1), editcap(1), mergecap(1), capinfos(1), pcap(3),
       pcap-filter(7) or tcpdump(8)

NOTES
       Dumpcap 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:
       <http://www.wireshark.org/docs/man-pages>.

AUTHORS
       Dumpcap is derived from the Wireshark capturing engine code; see the
       list of authors in the Wireshark man page for a list of authors of that
       code.

1.10.3				  2013-09-09			    DUMPCAP(1)
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