1DUMPCAP(1) The Wireshark Network Analyzer DUMPCAP(1)
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6 dumpcap - Dump network traffic
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9 dumpcap [ -a <capture autostop condition> ] ...
10 [ -b <capture ring buffer option>] ... [ -B <capture buffer size> ]
11 [ -c <capture packet count> ] [ -C <byte limit> ] [ -d ] [ -D ]
12 [ -f <capture filter> ] [ -g ] [ -h ]
13 [ -i <capture interface>|rpcap://<host>:<port>/<capture interface>|TCP@<host>:<port>|- ]
14 [ -I ] [ -L ] [ -M ] [ -n ] [ -N <packet limit> ] [ -p ] [ -P ] [ -q ]
15 [ -s <capture snaplen> ] [ -S ] [ -t ] [ -v ] [ -w <outfile> ]
16 [ -y <capture link type> ] [ --capture-comment <comment> ]
17 [ --list-time-stamp-types ] [ --time-stamp-type <type> ]
18
20 Dumpcap is a network traffic dump tool. It lets you capture packet
21 data from a live network and write the packets to a file. Dumpcap's
22 default capture file format is pcapng format. When the -P option is
23 specified, the output file is written in the pcap format.
24 Without any options set it will use the libpcap, Npcap, or WinPcap
26 library to capture traffic from the first available network interface
27 and writes the received raw packet data, along with the packets' time
28 stamps into a pcap file.
29 If the -w option is not specified, Dumpcap writes to a newly created
31 pcap file with a randomly chosen name. If the -w option is specified,
32 Dumpcap writes to the file specified by that option.
33 Packet capturing is performed with the pcap library. The capture
35 filter syntax follows the rules of the pcap library.
36
38 -a <capture autostop condition>
39 Specify a criterion that specifies when Dumpcap is to stop writing
40 to a capture file. The criterion is of the form test:value, where
41 test is one of:
42 duration:value Stop writing to a capture file after value seconds
44 have elapsed. Floating point values (e.g. 0.5) are allowed.
45 files:value Stop writing to capture files after value number of
47 files were written.
48 filesize:value Stop writing to a capture file after it reaches a
50 size of value kB. If this option is used together with the -b
51 option, dumpcap will stop writing to the current capture file and
52 switch to the next one if filesize is reached. Note that the
53 filesize is limited to a maximum value of 2 GiB.
54 packets:value Stop writing to a capture file after value packets
56 have been written. Same as -c <capture packet count>.
57 -b <capture ring buffer option>
59 Cause Dumpcap to run in "multiple files" mode. In "multiple files"
60 mode, Dumpcap will write to several capture files. When the first
61 capture file fills up, Dumpcap will switch writing to the next file
62 and so on.
63 The created filenames are based on the filename given with the -w
65 option, the number of the file and on the creation date and time,
66 e.g. outfile_00001_20190714120117.pcap,
67 outfile_00002_20190714120523.pcap, ...
68 With the files option it's also possible to form a "ring buffer".
70 This will fill up new files until the number of files specified, at
71 which point Dumpcap will discard the data in the first file and
72 start writing to that file and so on. If the files option is not
73 set, new files filled up until one of the capture stop conditions
74 match (or until the disk is full).
75 The criterion is of the form key:value, where key is one of:
77 duration:value switch to the next file after value seconds have
79 elapsed, even if the current file is not completely filled up.
80 Floating point values (e.g. 0.5) are allowed.
81 files:value begin again with the first file after value number of
83 files were written (form a ring buffer). This value must be less
84 than 100000. Caution should be used when using large numbers of
85 files: some filesystems do not handle many files in a single
86 directory well. The files criterion requires either duration,
87 interval or filesize to be specified to control when to go to the
88 next file. It should be noted that each -b parameter takes exactly
89 one criterion; to specify two criterion, each must be preceded by
90 the -b option.
91 filesize:value switch to the next file after it reaches a size of
93 value kB. Note that the filesize is limited to a maximum value of
94 2 GiB.
95 interval:value switch to the next file when the time is an exact
97 multiple of value seconds
98 packets:value switch to the next file after it contains value
100 packets.
101 Example: -b filesize:1000 -b files:5 results in a ring buffer of
103 five files of size one megabyte each.
104 -B <capture buffer size>
106 Set capture buffer size (in MiB, default is 2 MiB). This is used
107 by the capture driver to buffer packet data until that data can be
108 written to disk. If you encounter packet drops while capturing,
109 try to increase this size. Note that, while Dumpcap attempts to
110 set the buffer size to 2 MiB by default, and can be told to set it
111 to a larger value, the system or interface on which you're
112 capturing might silently limit the capture buffer size to a lower
113 value or raise it to a higher value.
114 This is available on UNIX systems with libpcap 1.0.0 or later and
116 on Windows. It is not available on UNIX systems with earlier
117 versions of libpcap.
118 This option can occur multiple times. If used before the first
120 occurrence of the -i option, it sets the default capture buffer
121 size. If used after an -i option, it sets the capture buffer size
122 for the interface specified by the last -i option occurring before
123 this option. If the capture buffer size is not set specifically,
124 the default capture buffer size is used instead.
125 -c <capture packet count>
127 Set the maximum number of packets to read when capturing live data.
128 Same as -a packets:<capture packet count>.
129 -C <byte limit>
131 Limit the amount of memory in bytes used for storing captured
132 packets in memory while processing it. If used in combination with
133 the -N option, both limits will apply. Setting this limit will
134 enable the usage of the separate thread per interface.
135 -d Dump the code generated for the capture filter in a human-readable
137 form, and exit.
138 -D Print a list of the interfaces on which Dumpcap can capture, and
140 exit. For each network interface, a number and an interface name,
141 possibly followed by a text description of the interface, is
142 printed. The interface name or the number can be supplied to the
143 -i option to specify an interface on which to capture.
144 This can be useful on systems that don't have a command to list
146 them (UNIX systems lacking ifconfig -a or Linux systems lacking ip
147 link show). The number can be useful on Windows systems, where the
148 interface name might be a long name or a GUID.
149 Note that "can capture" means that Dumpcap was able to open that
151 device to do a live capture. Depending on your system you may need
152 to run dumpcap from an account with special privileges (for
153 example, as root) to be able to capture network traffic. If
154 "dumpcap -D" is not run from such an account, it will not list any
155 interfaces.
156 -f <capture filter>
158 Set the capture filter expression.
159 The entire filter expression must be specified as a single argument
161 (which means that if it contains spaces, it must be quoted).
162 This option can occur multiple times. If used before the first
164 occurrence of the -i option, it sets the default capture filter
165 expression. If used after an -i option, it sets the capture filter
166 expression for the interface specified by the last -i option
167 occurring before this option. If the capture filter expression is
168 not set specifically, the default capture filter expression is used
169 if provided.
170 Pre-defined capture filter names, as shown in the GUI menu item
172 Capture->Capture Filters, can be used by prefixing the argument
173 with "predef:". Example: -f "predef:MyPredefinedHostOnlyFilter"
174 -g This option causes the output file(s) to be created with group-read
176 permission (meaning that the output file(s) can be read by other
177 members of the calling user's group).
178 -h Print the version and options and exits.
180 -i <capture interface>|rpcap://<host>:<port>/<capture
182 interface>|TCP@<host>:<port>|-
183 Set the name of the network interface or pipe to use for live
184 packet capture.
185 Network interface names should match one of the names listed in
187 "dumpcap -D" (described above); a number, as reported by "dumpcap
188 -D", can also be used. If you're using UNIX, "netstat -i",
189 "ifconfig -a" or "ip link" might also work to list interface names,
190 although not all versions of UNIX support the -a option to
191 ifconfig.
192 If no interface is specified, Dumpcap searches the list of
194 interfaces, choosing the first non-loopback interface if there are
195 any non-loopback interfaces, and choosing the first loopback
196 interface if there are no non-loopback interfaces. If there are no
197 interfaces at all, Dumpcap reports an error and doesn't start the
198 capture.
199 Pipe names should be either the name of a FIFO (named pipe) or "-"
201 to read data from the standard input. On Windows systems, pipe
202 names must be of the form "\\pipe\.\pipename". Data read from
203 pipes must be in standard pcapng or pcap format. Pcapng data must
204 have the same endianness as the capturing host.
205 This option can occur multiple times. When capturing from multiple
207 interfaces, the capture file will be saved in pcapng format.
208 -I Put the interface in "monitor mode"; this is supported only on IEEE
210 802.11 Wi-Fi interfaces, and supported only on some operating
211 systems.
212 Note that in monitor mode the adapter might disassociate from the
214 network with which it's associated, so that you will not be able to
215 use any wireless networks with that adapter. This could prevent
216 accessing files on a network server, or resolving host names or
217 network addresses, if you are capturing in monitor mode and are not
218 connected to another network with another adapter.
219 This option can occur multiple times. If used before the first
221 occurrence of the -i option, it enables the monitor mode for all
222 interfaces. If used after an -i option, it enables the monitor
223 mode for the interface specified by the last -i option occurring
224 before this option.
225 -L List the data link types supported by the interface and exit. The
227 reported link types can be used for the -y option.
228 -M When used with -D, -L, -S or --list-time-stamp-types print machine-
230 readable output. The machine-readable output is intended to be
231 read by Wireshark and TShark; its format is subject to change from
232 release to release.
233 -n Save files as pcapng. This is the default.
235 -N <packet limit>
237 Limit the number of packets used for storing captured packets in
238 memory while processing it. If used in combination with the -C
239 option, both limits will apply. Setting this limit will enable the
240 usage of the separate thread per interface.
241 -p Don't put the interface into promiscuous mode. Note that the
243 interface might be in promiscuous mode for some other reason;
244 hence, -p cannot be used to ensure that the only traffic that is
245 captured is traffic sent to or from the machine on which Dumpcap is
246 running, broadcast traffic, and multicast traffic to addresses
247 received by that machine.
248 This option can occur multiple times. If used before the first
250 occurrence of the -i option, no interface will be put into the
251 promiscuous mode. If used after an -i option, the interface
252 specified by the last -i option occurring before this option will
253 not be put into the promiscuous mode.
254 -P Save files as pcap instead of the default pcapng. In situations
256 that require pcapng, such as capturing from multiple interfaces,
257 this option will be overridden.
258 -q When capturing packets, don't display the continuous count of
260 packets captured that is normally shown when saving a capture to a
261 file; instead, just display, at the end of the capture, a count of
262 packets captured. On systems that support the SIGINFO signal, such
263 as various BSDs, you can cause the current count to be displayed by
264 typing your "status" character (typically control-T, although it
265 might be set to "disabled" by default on at least some BSDs, so
266 you'd have to explicitly set it to use it).
267 -s <capture snaplen>
269 Set the default snapshot length to use when capturing live data.
270 No more than snaplen bytes of each network packet will be read into
271 memory, or saved to disk. A value of 0 specifies a snapshot length
272 of 262144, so that the full packet is captured; this is the
273 default.
274 This option can occur multiple times. If used before the first
276 occurrence of the -i option, it sets the default snapshot length.
277 If used after an -i option, it sets the snapshot length for the
278 interface specified by the last -i option occurring before this
279 option. If the snapshot length is not set specifically, the default
280 snapshot length is used if provided.
281 -S Print statistics for each interface once every second.
283 -t Use a separate thread per interface.
285 -v Print the version and exit.
287 -w <outfile>
289 Write raw packet data to outfile. Use "-" for stdout.
290 -y <capture link type>
292 Set the data link type to use while capturing packets. The values
293 reported by -L are the values that can be used.
294 This option can occur multiple times. If used before the first
296 occurrence of the -i option, it sets the default capture link type.
297 If used after an -i option, it sets the capture link type for the
298 interface specified by the last -i option occurring before this
299 option. If the capture link type is not set specifically, the
300 default capture link type is used if provided.
301 --capture-comment <comment>
303 Add a capture comment to the output file.
304 This option is only available if we output the captured packets to
306 a single file in pcapng format. Only one capture comment may be set
307 per output file.
308 --list-time-stamp-types
310 List time stamp types supported for the interface. If no time stamp
311 type can be set, no time stamp types are listed.
312 --time-stamp-type <type>
314 Change the interface's timestamp method.
315
317 See the manual page of pcap-filter(7) or, if that doesn't exist,
318 tcpdump(8), or, if that doesn't exist,
319 <https://wiki.wireshark.org/CaptureFilters>.
320
322 wireshark(1), tshark(1), editcap(1), mergecap(1), capinfos(1), pcap(3),
323 pcap-filter(7) or tcpdump(8)
324
326 Dumpcap is part of the Wireshark distribution. The latest version of
327 Wireshark can be found at <https://www.wireshark.org>.
328 HTML versions of the Wireshark project man pages are available at:
330 <https://www.wireshark.org/docs/man-pages>.
331
333 Dumpcap is derived from the Wireshark capturing engine code; see the
334 list of authors in the Wireshark man page for a list of authors of that
335 code.
3363.0.5 2019-10-30 DUMPCAP(1)