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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>	] [ --capture-comment <comment>	]

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 kB. 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 kB.  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:1000 -b	files:5	results	in a ring buffer of
	   five	files of size one megabyte each.

       -B  <capture buffer size>
	   Set capture buffer size (in MiB, default is 2 MiB).	This is	used
	   by 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 2 MiB	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 instead.

       -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.

	   Pre-defined capture filter names, as	shown in the GUI menu item
	   Capture->Capture Filters, can be used by prefixing the argument
	   with	"predef:".  Example: -f	"predef:MyPredefinedHostOnlyFilter"

       -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. Use "-" for stdout.

       -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-comment <comment>
	   Add a capture comment to the	output file.

	   This	option is only available if we output the captured packets to
	   a single file in pcap-ng format. Only one capture comment may be
	   set per output file.

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,
       <https://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 <https://www.wireshark.org>.

       HTML versions of	the Wireshark project man pages	are available at:
       <https://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.

2.2.7				  2017-06-01			    DUMPCAP(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CAPTURE FILTER SYNTAX | SEE ALSO | NOTES | AUTHORS

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