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DUMPCAP(1)							    DUMPCAP(1)

NAME
       dumpcap - Dump network traffic

SYNOPSIS
       dumpcap [ -a|--autostop <capture	autostop condition> ] ...
       [ -b|--ring-buffer <capture ring	buffer option> ] ...
       [ -B|--buffer-size <capture buffer size>	]
       [ -c <capture packet count> ] [ -C <byte	limit> ] [ -d ]
       [ -D|--list-interfaces ]	[ -f <capture filter> ]	[ -g ] [ -h|--help ]
       [ -i|--interface	<capture interface>|rpcap://<host>:<port>/<capture interface>|TCP@<host>:<port>|- ]
       [ -I|--monitor-mode ]
       [ -k <freq>,[<type>],[<center_freq1>],[<center_freq2>] ]
       [ -L|--list-data-link-types ] [ -M ] [ -n ] [ -N	<packet	limit> ]
       [ -p|--no-promiscuous-mode ] [ --ifdescr	<description> ]
       [ --ifname <name> ] [ -P	] [ -q ]
       [ -s|--snapshot-length <capture snaplen>	] [ -S ] [ -t ]
       [ -v|--version ]	[ -w <outfile> ] [ -y|--linktype <capture link type> ]
       [ --capture-comment <comment> ] [ --list-time-stamp-types ]
       [ --time-stamp-type <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 pcapng 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,	Npcap, or 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|--autostop  <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. Floating point	values (e.g. 0.5) are allowed.

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

	   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.

	   packets:value Stop writing to a capture file	after value packets
	   have	been written. Same as -c <capture packet count>.

       -b|--ring-buffer	 <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_20220714120117.pcap,
	   outfile_00002_20220714120523.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.
	   Floating point values (e.g. 0.5) are	allowed.

	   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,
	   interval 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.

	   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.

	   interval:value switch to the	next file when the time	is an exact
	   multiple of value seconds. For example, use 3600 to switch to a new
	   file	every hour on the hour.

	   packets:value switch	to the next file after it contains value
	   packets.

	   printname:filename print the	name of	the most recently written file
	   to filename after the file is closed. filename can be stdout	or -
	   for standard	output,	or stderr for standard error.

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

       -B|--buffer-size	 <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.
	   Same	as -a packets:<capture packet count>.

       -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|--list-interfaces

	   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	(UNIX systems lacking ifconfig -a or Linux systems lacking ip
	   link	show). The number can be useful	on Windows systems, where the
	   interface name might	be a long name or a GUID.

	   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|--help

	   Print the version and options and exits.

       -i|--interface  <capture	interface>|rpcap://<host>:<port>/<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",
	   "ifconfig -a" or "ip	link" 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. On Windows systems, pipe
	   names must be of the	form "\\pipe\.*pipename*". Data	read from
	   pipes must be in standard pcapng or pcap format. Pcapng data	must
	   have	the same endianness as the capturing host.

	   "TCP@<host>:<port>" causes Dumpcap to attempt to connect to the
	   specified port on the specified host	and read pcapng	or pcap	data.

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

       --ifdescr> <description>

	   Use description as the description in the capture file for the
	   interface or	pipe specified before it with -i.

       --ifname> <name>

	   Use name as the name	in the capture file for	the the	interface or
	   pipe	specified before it with -i.

       -I|--monitor-mode

	   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.

       -k  <freq>,[<type>],[<center_freq1>],[<center_freq2>>

	   Set the channel on the interface; this is supported only on IEEE
	   802.11 Wi-Fi	interfaces, and	supported only on some operating
	   systems.

	   freq	is the frequency of the	channel. type is the type of the
	   channel, for	802.11n	and 802.11ac. The values for type are

       NOHT

	   Used	for non-802.11n/non-802.1ac channels

       HT20

	   20 MHz channel

       HT40-

	   40 MHz primary channel and a	lower secondary	channel

       HT40+

	   40 MHz primary channel and a	higher secondary channel

       HT80

	   80 MHz channel, with	centerfreq1 as its center frequency

       VHT80+80

	   two 80 MHz channels combined, with centerfreq1 and centerfreq2 as
	   the center frequencies of the two channels

       VHT160

	   160 MHz channel, with centerfreq1 as	its center frequency

       -L|--list-data-link-types

	   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, -S or	--list-time-stamp-types	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 pcapng. 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|--no-promiscuous-mode

	   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 pcapng. In	situations
	   that	require	pcapng,	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|--snapshot-length  <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 262144, 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|--version

	   Print the version and exit.

       -w  <outfile>

	   Write raw packet data to outfile. Use "-" for stdout.

       -y|--linktype  <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, if	supported by the
	   output file format.

	   This	option is only available if we output the captured packets to
	   a single file.

	   This	option may be specified	multiple times.	Note that Wireshark
	   currently only displays the first comment of	a capture file.

       --list-time-stamp-types

	   List	time stamp types supported for the interface. If no time stamp
	   type	can be set, no time stamp types	are listed.

       --time-stamp-type  <type>

	   Change the interface's timestamp method.

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://gitlab.com/wireshark/wireshark/-/wikis/CaptureFilters.

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

NOTES
       This is the manual page for Dumpcap 3.6.3. 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.

				  2022-03-23			    DUMPCAP(1)

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

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