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/WinPcap library to
26 capture traffic from the first available network interface and writes
27 the received raw packet data, along with the packets' time stamps into
28 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.
45 filesize:value Stop writing to a capture file after it reaches a
47 size of value kB. If this option is used together with the -b
48 option, dumpcap will stop writing to the current capture file and
49 switch to the next one if filesize is reached. Note that the
50 filesize is limited to a maximum value of 2 GiB.
51 files:value Stop writing to capture files after value number of
53 files were written.
54 -b <capture ring buffer option>
56 Cause Dumpcap to run in "multiple files" mode. In "multiple files"
57 mode, Dumpcap will write to several capture files. When the first
58 capture file fills up, Dumpcap will switch writing to the next file
59 and so on.
60 The created filenames are based on the filename given with the -w
62 option, the number of the file and on the creation date and time,
63 e.g. outfile_00001_20050604120117.pcap,
64 outfile_00002_20050604120523.pcap, ...
65 With the files option it's also possible to form a "ring buffer".
67 This will fill up new files until the number of files specified, at
68 which point Dumpcap will discard the data in the first file and
69 start writing to that file and so on. If the files option is not
70 set, new files filled up until one of the capture stop conditions
71 match (or until the disk is full).
72 The criterion is of the form key:value, where key is one of:
74 duration:value switch to the next file after value seconds have
76 elapsed, even if the current file is not completely filled up.
77 interval:value switch to the next file when the time is an exact
79 multiple of value seconds
80 filesize:value switch to the next file after it reaches a size of
82 value kB. Note that the filesize is limited to a maximum value of
83 2 GiB.
84 files:value begin again with the first file after value number of
86 files were written (form a ring buffer). This value must be less
87 than 100000. Caution should be used when using large numbers of
88 files: some filesystems do not handle many files in a single
89 directory well. The files criterion requires either duration,
90 interval or filesize to be specified to control when to go to the
91 next file. It should be noted that each -b parameter takes exactly
92 one criterion; to specify two criterion, each must be preceded by
93 the -b option.
94 Example: -b filesize:1000 -b files:5 results in a ring buffer of
96 five files of size one megabyte each.
97 -B <capture buffer size>
99 Set capture buffer size (in MiB, default is 2 MiB). This is used
100 by the capture driver to buffer packet data until that data can be
101 written to disk. If you encounter packet drops while capturing,
102 try to increase this size. Note that, while Dumpcap attempts to
103 set the buffer size to 2 MiB by default, and can be told to set it
104 to a larger value, the system or interface on which you're
105 capturing might silently limit the capture buffer size to a lower
106 value or raise it to a higher value.
107 This is available on UNIX systems with libpcap 1.0.0 or later and
109 on Windows. It is not available on UNIX systems with earlier
110 versions of libpcap.
111 This option can occur multiple times. If used before the first
113 occurrence of the -i option, it sets the default capture buffer
114 size. If used after an -i option, it sets the capture buffer size
115 for the interface specified by the last -i option occurring before
116 this option. If the capture buffer size is not set specifically,
117 the default capture buffer size is used instead.
118 -c <capture packet count>
120 Set the maximum number of packets to read when capturing live data.
121 -C <byte limit>
123 Limit the amount of memory in bytes used for storing captured
124 packets in memory while processing it. If used in combination with
125 the -N option, both limits will apply. Setting this limit will
126 enable the usage of the separate thread per interface.
127 -d Dump the code generated for the capture filter in a human-readable
129 form, and exit.
130 -D Print a list of the interfaces on which Dumpcap can capture, and
132 exit. For each network interface, a number and an interface name,
133 possibly followed by a text description of the interface, is
134 printed. The interface name or the number can be supplied to the
135 -i option to specify an interface on which to capture.
136 This can be useful on systems that don't have a command to list
138 them (UNIX systems lacking ifconfig -a or Linux systems lacking ip
139 link show). The number can be useful on Windows systems, where the
140 interface name might be a long name or a GUID.
141 Note that "can capture" means that Dumpcap was able to open that
143 device to do a live capture. Depending on your system you may need
144 to run dumpcap from an account with special privileges (for
145 example, as root) to be able to capture network traffic. If
146 "dumpcap -D" is not run from such an account, it will not list any
147 interfaces.
148 -f <capture filter>
150 Set the capture filter expression.
151 The entire filter expression must be specified as a single argument
153 (which means that if it contains spaces, it must be quoted).
154 This option can occur multiple times. If used before the first
156 occurrence of the -i option, it sets the default capture filter
157 expression. If used after an -i option, it sets the capture filter
158 expression for the interface specified by the last -i option
159 occurring before this option. If the capture filter expression is
160 not set specifically, the default capture filter expression is used
161 if provided.
162 Pre-defined capture filter names, as shown in the GUI menu item
164 Capture->Capture Filters, can be used by prefixing the argument
165 with "predef:". Example: -f "predef:MyPredefinedHostOnlyFilter"
166 -g This option causes the output file(s) to be created with group-read
168 permission (meaning that the output file(s) can be read by other
169 members of the calling user's group).
170 -h Print the version and options and exits.
172 -i <capture interface>|rpcap://<host>:<port>/<capture
174 interface>|TCP@<host>:<port>|-
175 Set the name of the network interface or pipe to use for live
176 packet capture.
177 Network interface names should match one of the names listed in
179 "dumpcap -D" (described above); a number, as reported by "dumpcap
180 -D", can also be used. If you're using UNIX, "netstat -i" or
181 "ifconfig -a" might also work to list interface names, although not
182 all versions of UNIX support the -a option to ifconfig.
183 If no interface is specified, Dumpcap searches the list of
185 interfaces, choosing the first non-loopback interface if there are
186 any non-loopback interfaces, and choosing the first loopback
187 interface if there are no non-loopback interfaces. If there are no
188 interfaces at all, Dumpcap reports an error and doesn't start the
189 capture.
190 Pipe names should be either the name of a FIFO (named pipe) or
192 ``-'' to read data from the standard input. Data read from pipes
193 must be in standard pcap format.
194 This option can occur multiple times. When capturing from multiple
196 interfaces, the capture file will be saved in pcapng format.
197 Note: the Win32 version of Dumpcap doesn't support capturing from
199 pipes or stdin!
200 -I Put the interface in "monitor mode"; this is supported only on IEEE
202 802.11 Wi-Fi interfaces, and supported only on some operating
203 systems.
204 Note that in monitor mode the adapter might disassociate from the
206 network with which it's associated, so that you will not be able to
207 use any wireless networks with that adapter. This could prevent
208 accessing files on a network server, or resolving host names or
209 network addresses, if you are capturing in monitor mode and are not
210 connected to another network with another adapter.
211 This option can occur multiple times. If used before the first
213 occurrence of the -i option, it enables the monitor mode for all
214 interfaces. If used after an -i option, it enables the monitor
215 mode for the interface specified by the last -i option occurring
216 before this option.
217 -L List the data link types supported by the interface and exit. The
219 reported link types can be used for the -y option.
220 -M When used with -D, -L, -S or --list-time-stamp-types print machine-
222 readable output. The machine-readable output is intended to be
223 read by Wireshark and TShark; its format is subject to change from
224 release to release.
225 -n Save files as pcapng. This is the default.
227 -N <packet limit>
229 Limit the number of packets used for storing captured packets in
230 memory while processing it. If used in combination with the -C
231 option, both limits will apply. Setting this limit will enable the
232 usage of the separate thread per interface.
233 -p Don't put the interface into promiscuous mode. Note that the
235 interface might be in promiscuous mode for some other reason;
236 hence, -p cannot be used to ensure that the only traffic that is
237 captured is traffic sent to or from the machine on which Dumpcap is
238 running, broadcast traffic, and multicast traffic to addresses
239 received by that machine.
240 This option can occur multiple times. If used before the first
242 occurrence of the -i option, no interface will be put into the
243 promiscuous mode. If used after an -i option, the interface
244 specified by the last -i option occurring before this option will
245 not be put into the promiscuous mode.
246 -P Save files as pcap instead of the default pcapng. In situations
248 that require pcapng, such as capturing from multiple interfaces,
249 this option will be overridden.
250 -q When capturing packets, don't display the continuous count of
252 packets captured that is normally shown when saving a capture to a
253 file; instead, just display, at the end of the capture, a count of
254 packets captured. On systems that support the SIGINFO signal, such
255 as various BSDs, you can cause the current count to be displayed by
256 typing your "status" character (typically control-T, although it
257 might be set to "disabled" by default on at least some BSDs, so
258 you'd have to explicitly set it to use it).
259 -s <capture snaplen>
261 Set the default snapshot length to use when capturing live data.
262 No more than snaplen bytes of each network packet will be read into
263 memory, or saved to disk. A value of 0 specifies a snapshot length
264 of 262144, so that the full packet is captured; this is the
265 default.
266 This option can occur multiple times. If used before the first
268 occurrence of the -i option, it sets the default snapshot length.
269 If used after an -i option, it sets the snapshot length for the
270 interface specified by the last -i option occurring before this
271 option. If the snapshot length is not set specifically, the default
272 snapshot length is used if provided.
273 -S Print statistics for each interface once every second.
275 -t Use a separate thread per interface.
277 -v Print the version and exit.
279 -w <outfile>
281 Write raw packet data to outfile. Use "-" for stdout.
282 -y <capture link type>
284 Set the data link type to use while capturing packets. The values
285 reported by -L are the values that can be used.
286 This option can occur multiple times. If used before the first
288 occurrence of the -i option, it sets the default capture link type.
289 If used after an -i option, it sets the capture link type for the
290 interface specified by the last -i option occurring before this
291 option. If the capture link type is not set specifically, the
292 default capture link type is used if provided.
293 --capture-comment <comment>
295 Add a capture comment to the output file.
296 This option is only available if we output the captured packets to
298 a single file in pcapng format. Only one capture comment may be set
299 per output file.
300 --list-time-stamp-types
302 List time stamp types supported for the interface. If no time stamp
303 type can be set, no time stamp types are listed.
304 --time-stamp-type <type>
306 Change the interface's timestamp method.
307
309 See the manual page of pcap-filter(7) or, if that doesn't exist,
310 tcpdump(8), or, if that doesn't exist,
311 <https://wiki.wireshark.org/CaptureFilters>.
312
314 wireshark(1), tshark(1), editcap(1), mergecap(1), capinfos(1), pcap(3),
315 pcap-filter(7) or tcpdump(8)
316
318 Dumpcap is part of the Wireshark distribution. The latest version of
319 Wireshark can be found at <https://www.wireshark.org>.
320 HTML versions of the Wireshark project man pages are available at:
322 <https://www.wireshark.org/docs/man-pages>.
323
325 Dumpcap is derived from the Wireshark capturing engine code; see the
326 list of authors in the Wireshark man page for a list of authors of that
327 code.
3282.6.2 2018-07-18 DUMPCAP(1)