1DUMPCAP(1) The Wireshark Network Analyzer DUMPCAP(1)
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6 dumpcap - Dump network traffic
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9 dumpcap [ -a|--autostop <capture autostop condition> ] ...
10 [ -b|--ring-buffer <capture ring buffer option>] ...
11 [ -B|--buffer-size <capture buffer size> ]
12 [ -c <capture packet count> ] [ -C <byte limit> ] [ -d ]
13 [ -D|--list-interfaces ] [ -f <capture filter> ] [ -g ] [ -h|--help ]
14 [ -i|--interface <capture interface>|rpcap://<host>:<port>/<capture interface>|TCP@<host>:<port>|- ]
15 [ -i|--interface <capture interface>|rpcap://<host>:<port>/<capture interface>|TCP@<host>:<port>|- ]
16 [ -I|--monitor-mode ]
17 [ -k <freq>,[<type>],[<center_freq1>],[<center_freq2>]
18 [ -L|--list-data-link-types ] [ -M ] [ -n ] [ -N <packet limit> ]
19 [ -p|--no-promiscuous-mode ] [ -P ] [ -q ]
20 [ -s|--snapshot-length <capture snaplen> ] [ -S ] [ -t ]
21 [ -v|--version ] [ -w <outfile> ] [ -y|--linktype <capture link type> ]
22 [ --capture-comment <comment> ] [ --list-time-stamp-types ]
23 [ --time-stamp-type <type> ]
24
26 Dumpcap is a network traffic dump tool. It lets you capture packet
27 data from a live network and write the packets to a file. Dumpcap's
28 default capture file format is pcapng format. When the -P option is
29 specified, the output file is written in the pcap format.
30 Without any options set it will use the libpcap, Npcap, or WinPcap
32 library to capture traffic from the first available network interface
33 and writes the received raw packet data, along with the packets' time
34 stamps into a pcap file.
35 If the -w option is not specified, Dumpcap writes to a newly created
37 pcap file with a randomly chosen name. If the -w option is specified,
38 Dumpcap writes to the file specified by that option.
39 Packet capturing is performed with the pcap library. The capture
41 filter syntax follows the rules of the pcap library.
42
44 -a|--autostop <capture autostop condition>
45 Specify a criterion that specifies when Dumpcap is to stop writing
46 to a capture file. The criterion is of the form test:value, where
47 test is one of:
48 duration:value Stop writing to a capture file after value seconds
50 have elapsed. Floating point values (e.g. 0.5) are allowed.
51 files:value Stop writing to capture files after value number of
53 files were written.
54 filesize:value Stop writing to a capture file after it reaches a
56 size of value kB. If this option is used together with the -b
57 option, dumpcap will stop writing to the current capture file and
58 switch to the next one if filesize is reached. Note that the
59 filesize is limited to a maximum value of 2 GiB.
60 packets:value Stop writing to a capture file after value packets
62 have been written. Same as -c <capture packet count>.
63 -b|--ring-buffer <capture ring buffer option>
65 Cause Dumpcap to run in "multiple files" mode. In "multiple files"
66 mode, Dumpcap will write to several capture files. When the first
67 capture file fills up, Dumpcap will switch writing to the next file
68 and so on.
69 The created filenames are based on the filename given with the -w
71 option, the number of the file and on the creation date and time,
72 e.g. outfile_00001_20200714120117.pcap,
73 outfile_00002_20200714120523.pcap, ...
74 With the files option it's also possible to form a "ring buffer".
76 This will fill up new files until the number of files specified, at
77 which point Dumpcap will discard the data in the first file and
78 start writing to that file and so on. If the files option is not
79 set, new files filled up until one of the capture stop conditions
80 match (or until the disk is full).
81 The criterion is of the form key:value, where key is one of:
83 duration:value switch to the next file after value seconds have
85 elapsed, even if the current file is not completely filled up.
86 Floating point values (e.g. 0.5) are allowed.
87 files:value begin again with the first file after value number of
89 files were written (form a ring buffer). This value must be less
90 than 100000. Caution should be used when using large numbers of
91 files: some filesystems do not handle many files in a single
92 directory well. The files criterion requires either duration,
93 interval or filesize to be specified to control when to go to the
94 next file. It should be noted that each -b parameter takes exactly
95 one criterion; to specify two criterion, each must be preceded by
96 the -b option.
97 filesize:value switch to the next file after it reaches a size of
99 value kB. Note that the filesize is limited to a maximum value of
100 2 GiB.
101 interval:value switch to the next file when the time is an exact
103 multiple of value seconds. For example, use 3600 to switch to a
104 new file every hour on the hour.
105 packets:value switch to the next file after it contains value
107 packets.
108 Example: -b filesize:1000 -b files:5 results in a ring buffer of
110 five files of size one megabyte each.
111 -B|--buffer-size <capture buffer size>
113 Set capture buffer size (in MiB, default is 2 MiB). This is used
114 by the capture driver to buffer packet data until that data can be
115 written to disk. If you encounter packet drops while capturing,
116 try to increase this size. Note that, while Dumpcap attempts to
117 set the buffer size to 2 MiB by default, and can be told to set it
118 to a larger value, the system or interface on which you're
119 capturing might silently limit the capture buffer size to a lower
120 value or raise it to a higher value.
121 This is available on UNIX systems with libpcap 1.0.0 or later and
123 on Windows. It is not available on UNIX systems with earlier
124 versions of libpcap.
125 This option can occur multiple times. If used before the first
127 occurrence of the -i option, it sets the default capture buffer
128 size. If used after an -i option, it sets the capture buffer size
129 for the interface specified by the last -i option occurring before
130 this option. If the capture buffer size is not set specifically,
131 the default capture buffer size is used instead.
132 -c <capture packet count>
134 Set the maximum number of packets to read when capturing live data.
135 Same as -a packets:<capture packet count>.
136 -C <byte limit>
138 Limit the amount of memory in bytes used for storing captured
139 packets in memory while processing it. If used in combination with
140 the -N option, both limits will apply. Setting this limit will
141 enable the usage of the separate thread per interface.
142 -d Dump the code generated for the capture filter in a human-readable
144 form, and exit.
145 -D|--list-interfaces
147 Print a list of the interfaces on which Dumpcap can capture, and
148 exit. For each network interface, a number and an interface name,
149 possibly followed by a text description of the interface, is
150 printed. The interface name or the number can be supplied to the
151 -i option to specify an interface on which to capture.
152 This can be useful on systems that don't have a command to list
154 them (UNIX systems lacking ifconfig -a or Linux systems lacking ip
155 link show). The number can be useful on Windows systems, where the
156 interface name might be a long name or a GUID.
157 Note that "can capture" means that Dumpcap was able to open that
159 device to do a live capture. Depending on your system you may need
160 to run dumpcap from an account with special privileges (for
161 example, as root) to be able to capture network traffic. If
162 "dumpcap -D" is not run from such an account, it will not list any
163 interfaces.
164 -f <capture filter>
166 Set the capture filter expression.
167 The entire filter expression must be specified as a single argument
169 (which means that if it contains spaces, it must be quoted).
170 This option can occur multiple times. If used before the first
172 occurrence of the -i option, it sets the default capture filter
173 expression. If used after an -i option, it sets the capture filter
174 expression for the interface specified by the last -i option
175 occurring before this option. If the capture filter expression is
176 not set specifically, the default capture filter expression is used
177 if provided.
178 Pre-defined capture filter names, as shown in the GUI menu item
180 Capture->Capture Filters, can be used by prefixing the argument
181 with "predef:". Example: -f "predef:MyPredefinedHostOnlyFilter"
182 -g This option causes the output file(s) to be created with group-read
184 permission (meaning that the output file(s) can be read by other
185 members of the calling user's group).
186 -h|--help
188 Print the version and options and exits.
189 -i|--interface <capture interface>|rpcap://<host>:<port>/<capture
191 interface>|TCP@<host>:<port>|-
192 Set the name of the network interface or pipe to use for live
193 packet capture.
194 Network interface names should match one of the names listed in
196 "dumpcap -D" (described above); a number, as reported by "dumpcap
197 -D", can also be used. If you're using UNIX, "netstat -i",
198 "ifconfig -a" or "ip link" might also work to list interface names,
199 although not all versions of UNIX support the -a option to
200 ifconfig.
201 If no interface is specified, Dumpcap searches the list of
203 interfaces, choosing the first non-loopback interface if there are
204 any non-loopback interfaces, and choosing the first loopback
205 interface if there are no non-loopback interfaces. If there are no
206 interfaces at all, Dumpcap reports an error and doesn't start the
207 capture.
208 Pipe names should be either the name of a FIFO (named pipe) or "-"
210 to read data from the standard input. On Windows systems, pipe
211 names must be of the form "\\pipe\.\pipename". Data read from
212 pipes must be in standard pcapng or pcap format. Pcapng data must
213 have the same endianness as the capturing host.
214 This option can occur multiple times. When capturing from multiple
216 interfaces, the capture file will be saved in pcapng format.
217 -I|--monitor-mode
219 Put the interface in "monitor mode"; this is supported only on IEEE
220 802.11 Wi-Fi interfaces, and supported only on some operating
221 systems.
222 Note that in monitor mode the adapter might disassociate from the
224 network with which it's associated, so that you will not be able to
225 use any wireless networks with that adapter. This could prevent
226 accessing files on a network server, or resolving host names or
227 network addresses, if you are capturing in monitor mode and are not
228 connected to another network with another adapter.
229 This option can occur multiple times. If used before the first
231 occurrence of the -i option, it enables the monitor mode for all
232 interfaces. If used after an -i option, it enables the monitor
233 mode for the interface specified by the last -i option occurring
234 before this option.
235 -k <freq>,[<type>],[<center_freq1>],[<center_freq2>>
237 Set the channel on the interface; this is supported only on IEEE
238 802.11 Wi-Fi interfaces, and supported only on some operating
239 systems.
240 freq is the frequency of the channel. type is the type of the
242 channel, for 802.11n and 802.11ac. The values for type are
243 NOHT Used for non-802.11n/non-802.1ac channels
245 HT20 20 MHz channel
247 HT40- 40 MHz primary channel and a lower secondary channel
249 HT40+ 40 MHz primary channel and a higher secondary channel
251 HT80 80 MHz channel, with centerfreq1 as its center frequency
253 VHT80+80
255 two 80 MHz channels combined, with centerfreq1 and
256 centerfreq2 as the center frequencies of the two channels
257 VHT160 160 MHz channel, with centerfreq1 as its center frequency
259 -L|--list-data-link-types
261 List the data link types supported by the interface and exit. The
262 reported link types can be used for the -y option.
263 -M When used with -D, -L, -S or --list-time-stamp-types print machine-
265 readable output. The machine-readable output is intended to be
266 read by Wireshark and TShark; its format is subject to change from
267 release to release.
268 -n Save files as pcapng. This is the default.
270 -N <packet limit>
272 Limit the number of packets used for storing captured packets in
273 memory while processing it. If used in combination with the -C
274 option, both limits will apply. Setting this limit will enable the
275 usage of the separate thread per interface.
276 -p|--no-promiscuous-mode
278 Don't put the interface into promiscuous mode. Note that the
279 interface might be in promiscuous mode for some other reason;
280 hence, -p cannot be used to ensure that the only traffic that is
281 captured is traffic sent to or from the machine on which Dumpcap is
282 running, broadcast traffic, and multicast traffic to addresses
283 received by that machine.
284 This option can occur multiple times. If used before the first
286 occurrence of the -i option, no interface will be put into the
287 promiscuous mode. If used after an -i option, the interface
288 specified by the last -i option occurring before this option will
289 not be put into the promiscuous mode.
290 -P Save files as pcap instead of the default pcapng. In situations
292 that require pcapng, such as capturing from multiple interfaces,
293 this option will be overridden.
294 -q When capturing packets, don't display the continuous count of
296 packets captured that is normally shown when saving a capture to a
297 file; instead, just display, at the end of the capture, a count of
298 packets captured. On systems that support the SIGINFO signal, such
299 as various BSDs, you can cause the current count to be displayed by
300 typing your "status" character (typically control-T, although it
301 might be set to "disabled" by default on at least some BSDs, so
302 you'd have to explicitly set it to use it).
303 -s|--snapshot-length <capture snaplen>
305 Set the default snapshot length to use when capturing live data.
306 No more than snaplen bytes of each network packet will be read into
307 memory, or saved to disk. A value of 0 specifies a snapshot length
308 of 262144, so that the full packet is captured; this is the
309 default.
310 This option can occur multiple times. If used before the first
312 occurrence of the -i option, it sets the default snapshot length.
313 If used after an -i option, it sets the snapshot length for the
314 interface specified by the last -i option occurring before this
315 option. If the snapshot length is not set specifically, the default
316 snapshot length is used if provided.
317 -S Print statistics for each interface once every second.
319 -t Use a separate thread per interface.
321 -v|--version
323 Print the version and exit.
324 -w <outfile>
326 Write raw packet data to outfile. Use "-" for stdout.
327 -y|--linktype <capture link type>
329 Set the data link type to use while capturing packets. The values
330 reported by -L are the values that can be used.
331 This option can occur multiple times. If used before the first
333 occurrence of the -i option, it sets the default capture link type.
334 If used after an -i option, it sets the capture link type for the
335 interface specified by the last -i option occurring before this
336 option. If the capture link type is not set specifically, the
337 default capture link type is used if provided.
338 --capture-comment <comment>
340 Add a capture comment to the output file.
341 This option is only available if we output the captured packets to
343 a single file in pcapng format. Only one capture comment may be set
344 per output file.
345 --list-time-stamp-types
347 List time stamp types supported for the interface. If no time stamp
348 type can be set, no time stamp types are listed.
349 --time-stamp-type <type>
351 Change the interface's timestamp method.
352
354 See the manual page of pcap-filter(7) or, if that doesn't exist,
355 tcpdump(8), or, if that doesn't exist,
356 <https://wiki.wireshark.org/CaptureFilters>.
357
359 wireshark(1), tshark(1), editcap(1), mergecap(1), capinfos(1), pcap(3),
360 pcap-filter(7) or tcpdump(8)
361
363 Dumpcap is part of the Wireshark distribution. The latest version of
364 Wireshark can be found at <https://www.wireshark.org>.
365 HTML versions of the Wireshark project man pages are available at:
367 <https://www.wireshark.org/docs/man-pages>.
368
370 Dumpcap is derived from the Wireshark capturing engine code; see the
371 list of authors in the Wireshark man page for a list of authors of that
372 code.
3733.2.3 2020-04-13 DUMPCAP(1)