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>/<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> ]
17
19 Dumpcap is a network traffic dump tool. It lets you capture packet
20 data from a live network and write the packets to a file. Dumpcap's
21 default capture file format is pcap-ng format. When the -P option is
22 specified, the output file is written in the pcap format.
23 Without any options set it will use the libpcap/WinPcap library to
25 capture traffic from the first available network interface and writes
26 the received raw packet data, along with the packets' time stamps into
27 a pcap file.
28 If the -w option is not specified, Dumpcap writes to a newly created
30 pcap file with a randomly chosen name. If the -w option is specified,
31 Dumpcap writes to the file specified by that option.
32 Packet capturing is performed with the pcap library. The capture
34 filter syntax follows the rules of the pcap library.
35
37 -a <capture autostop condition>
38 Specify a criterion that specifies when Dumpcap is to stop writing
39 to a capture file. The criterion is of the form test:value, where
40 test is one of:
41 duration:value Stop writing to a capture file after value seconds
43 have elapsed.
44 filesize:value Stop writing to a capture file after it reaches a
46 size of value kB. If this option is used together with the -b
47 option, dumpcap will stop writing to the current capture file and
48 switch to the next one if filesize is reached. Note that the
49 filesize is limited to a maximum value of 2 GiB.
50 files:value Stop writing to capture files after value number of
52 files were written.
53 -b <capture ring buffer option>
55 Cause Dumpcap to run in "multiple files" mode. In "multiple files"
56 mode, Dumpcap will write to several capture files. When the first
57 capture file fills up, Dumpcap will switch writing to the next file
58 and so on.
59 The created filenames are based on the filename given with the -w
61 option, the number of the file and on the creation date and time,
62 e.g. outfile_00001_20050604120117.pcap,
63 outfile_00002_20050604120523.pcap, ...
64 With the files option it's also possible to form a "ring buffer".
66 This will fill up new files until the number of files specified, at
67 which point Dumpcap will discard the data in the first file and
68 start writing to that file and so on. If the files option is not
69 set, new files filled up until one of the capture stop conditions
70 match (or until the disk is full).
71 The criterion is of the form key:value, where key is one of:
73 duration:value switch to the next file after value seconds have
75 elapsed, even if the current file is not completely filled up.
76 filesize:value switch to the next file after it reaches a size of
78 value kB. Note that the filesize is limited to a maximum value of
79 2 GiB.
80 files:value begin again with the first file after value number of
82 files were written (form a ring buffer). This value must be less
83 than 100000. Caution should be used when using large numbers of
84 files: some filesystems do not handle many files in a single
85 directory well. The files criterion requires either duration or
86 filesize to be specified to control when to go to the next file.
87 It should be noted that each -b parameter takes exactly one
88 criterion; to specify two criterion, each must be preceded by the
89 -b option.
90 Example: -b filesize:1000 -b files:5 results in a ring buffer of
92 five files of size one megabyte each.
93 -B <capture buffer size>
95 Set capture buffer size (in MiB, default is 4 MiB). This is used
96 by the capture driver to buffer packet data until that data can be
97 written to disk. If you encounter packet drops while capturing,
98 try to increase this size. Note that, while Dumpcap attempts to
99 set the buffer size to 4 MiB by default, and can be told to set it
100 to a larger value, the system or interface on which you're
101 capturing might silently limit the capture buffer size to a lower
102 value or raise it to a higher value.
103 This is available on UNIX systems with libpcap 1.0.0 or later and
105 on Windows. It is not available on UNIX systems with earlier
106 versions of libpcap.
107 This option can occur multiple times. If used before the first
109 occurrence of the -i option, it sets the default capture buffer
110 size. If used after an -i option, it sets the capture buffer size
111 for the interface specified by the last -i option occurring before
112 this option. If the capture buffer size is not set specifically,
113 the default capture buffer size is used instead.
114 -c <capture packet count>
116 Set the maximum number of packets to read when capturing live data.
117 -C <byte limit>
119 Limit the amount of memory in bytes used for storing captured
120 packets in memory while processing it. If used in combination with
121 the -N option, both limits will apply. Setting this limit will
122 enable the usage of the separate thread per interface.
123 -d Dump the code generated for the capture filter in a human-readable
125 form, and exit.
126 -D Print a list of the interfaces on which Dumpcap can capture, and
128 exit. For each network interface, a number and an interface name,
129 possibly followed by a text description of the interface, is
130 printed. The interface name or the number can be supplied to the
131 -i option to specify an interface on which to capture.
132 This can be useful on systems that don't have a command to list
134 them (e.g., Windows systems, or UNIX systems lacking ifconfig -a);
135 the number can be useful on Windows 2000 and later systems, where
136 the interface name is a somewhat complex string.
137 Note that "can capture" means that Dumpcap was able to open that
139 device to do a live capture. Depending on your system you may need
140 to run dumpcap from an account with special privileges (for
141 example, as root) to be able to capture network traffic. If
142 "dumpcap -D" is not run from such an account, it will not list any
143 interfaces.
144 -f <capture filter>
146 Set the capture filter expression.
147 The entire filter expression must be specified as a single argument
149 (which means that if it contains spaces, it must be quoted).
150 This option can occur multiple times. If used before the first
152 occurrence of the -i option, it sets the default capture filter
153 expression. If used after an -i option, it sets the capture filter
154 expression for the interface specified by the last -i option
155 occurring before this option. If the capture filter expression is
156 not set specifically, the default capture filter expression is used
157 if provided.
158 -g This option causes the output file(s) to be created with group-read
160 permission (meaning that the output file(s) can be read by other
161 members of the calling user's group).
162 -h Print the version and options and exits.
164 -i <capture interface>|rpcap://<host>/<capture
166 interface>|TCP@<host>:<port>|-
167 Set the name of the network interface or pipe to use for live
168 packet capture.
169 Network interface names should match one of the names listed in
171 "dumpcap -D" (described above); a number, as reported by "dumpcap
172 -D", can also be used. If you're using UNIX, "netstat -i" or
173 "ifconfig -a" might also work to list interface names, although not
174 all versions of UNIX support the -a option to ifconfig.
175 If no interface is specified, Dumpcap searches the list of
177 interfaces, choosing the first non-loopback interface if there are
178 any non-loopback interfaces, and choosing the first loopback
179 interface if there are no non-loopback interfaces. If there are no
180 interfaces at all, Dumpcap reports an error and doesn't start the
181 capture.
182 Pipe names should be either the name of a FIFO (named pipe) or
184 ``-'' to read data from the standard input. Data read from pipes
185 must be in standard pcap format.
186 This option can occur multiple times. When capturing from multiple
188 interfaces, the capture file will be saved in pcap-ng format.
189 Note: the Win32 version of Dumpcap doesn't support capturing from
191 pipes or stdin!
192 -I Put the interface in "monitor mode"; this is supported only on IEEE
194 802.11 Wi-Fi interfaces, and supported only on some operating
195 systems.
196 Note that in monitor mode the adapter might disassociate from the
198 network with which it's associated, so that you will not be able to
199 use any wireless networks with that adapter. This could prevent
200 accessing files on a network server, or resolving host names or
201 network addresses, if you are capturing in monitor mode and are not
202 connected to another network with another adapter.
203 This option can occur multiple times. If used before the first
205 occurrence of the -i option, it enables the monitor mode for all
206 interfaces. If used after an -i option, it enables the monitor
207 mode for the interface specified by the last -i option occurring
208 before this option.
209 -L List the data link types supported by the interface and exit. The
211 reported link types can be used for the -y option.
212 -M When used with -D, -L or -S, print machine-readable output. The
214 machine-readable output is intended to be read by Wireshark and
215 TShark; its format is subject to change from release to release.
216 -n Save files as pcap-ng. This is the default.
218 -N <packet limit>
220 Limit the number of packets used for storing captured packets in
221 memory while processing it. If used in combination with the -C
222 option, both limits will apply. Setting this limit will enable the
223 usage of the separate thread per interface.
224 -p Don't put the interface into promiscuous mode. Note that the
226 interface might be in promiscuous mode for some other reason;
227 hence, -p cannot be used to ensure that the only traffic that is
228 captured is traffic sent to or from the machine on which Dumpcap is
229 running, broadcast traffic, and multicast traffic to addresses
230 received by that machine.
231 This option can occur multiple times. If used before the first
233 occurrence of the -i option, no interface will be put into the
234 promiscuous mode. If used after an -i option, the interface
235 specified by the last -i option occurring before this option will
236 not be put into the promiscuous mode.
237 -P Save files as pcap instead of the default pcap-ng. In situations
239 that require pcap-ng, such as capturing from multiple interfaces,
240 this option will be overridden.
241 -q When capturing packets, don't display the continuous count of
243 packets captured that is normally shown when saving a capture to a
244 file; instead, just display, at the end of the capture, a count of
245 packets captured. On systems that support the SIGINFO signal, such
246 as various BSDs, you can cause the current count to be displayed by
247 typing your "status" character (typically control-T, although it
248 might be set to "disabled" by default on at least some BSDs, so
249 you'd have to explicitly set it to use it).
250 -s <capture snaplen>
252 Set the default snapshot length to use when capturing live data.
253 No more than snaplen bytes of each network packet will be read into
254 memory, or saved to disk. A value of 0 specifies a snapshot length
255 of 262144, so that the full packet is captured; this is the
256 default.
257 This option can occur multiple times. If used before the first
259 occurrence of the -i option, it sets the default snapshot length.
260 If used after an -i option, it sets the snapshot length for the
261 interface specified by the last -i option occurring before this
262 option. If the snapshot length is not set specifically, the default
263 snapshot length is used if provided.
264 -S Print statistics for each interface once every second.
266 -t Use a separate thread per interface.
268 -v Print the version and exit.
270 -w <outfile>
272 Write raw packet data to outfile.
273 NOTE: The usage of "-" for stdout is not allowed here!
275 -y <capture link type>
277 Set the data link type to use while capturing packets. The values
278 reported by -L are the values that can be used.
279 This option can occur multiple times. If used before the first
281 occurrence of the -i option, it sets the default capture link type.
282 If used after an -i option, it sets the capture link type for the
283 interface specified by the last -i option occurring before this
284 option. If the capture link type is not set specifically, the
285 default capture link type is used if provided.
286
288 See the manual page of pcap-filter(7) or, if that doesn't exist,
289 tcpdump(8), or, if that doesn't exist,
290 <http://wiki.wireshark.org/CaptureFilters>.
291
293 wireshark(1), tshark(1), editcap(1), mergecap(1), capinfos(1), pcap(3),
294 pcap-filter(7) or tcpdump(8)
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297 Dumpcap is part of the Wireshark distribution. The latest version of
298 Wireshark can be found at <http://www.wireshark.org>.
299 HTML versions of the Wireshark project man pages are available at:
301 <http://www.wireshark.org/docs/man-pages>.
302
304 Dumpcap is derived from the Wireshark capturing engine code; see the
305 list of authors in the Wireshark man page for a list of authors of that
306 code.
3071.10.14 2018-10-30 DUMPCAP(1)