1EDITCAP(1) The Wireshark Network Analyzer EDITCAP(1)
2
6 editcap - Edit and/or translate the format of capture files
7
9 editcap [ -a <frame:comment> ] [ -A <start time> ] [ -B <stop time> ]
10 [ -c <packets per file> ] [ -C [offset:]<choplen> ]
11 [ -E <error probability> ] [ -F <file format> ] [ -h ]
12 [ -i <seconds per file> ] [ -o <change offset> ] [ -L ] [ -r ]
13 [ -s <snaplen> ] [ -S <strict time adjustment> ]
14 [ -t <time adjustment> ] [ -T <encapsulation type> ] [ -v ] infile
15 outfile [ packet#[-packet#] ... ]
16 editcap -d | -D <dup window> | -w <dup time window> [ -v ]
18 [ -I <bytes to ignore> ] infile outfile
19 editcap [ -V ]
21
23 Editcap is a program that reads some or all of the captured packets
24 from the infile, optionally converts them in various ways and writes
25 the resulting packets to the capture outfile (or outfiles).
26 By default, it reads all packets from the infile and writes them to the
28 outfile in pcap file format.
29 An optional list of packet numbers can be specified on the command
31 tail; individual packet numbers separated by whitespace and/or ranges
32 of packet numbers can be specified as start-end, referring to all
33 packets from start to end. By default the selected packets with those
34 numbers will not be written to the capture file. If the -r flag is
35 specified, the whole packet selection is reversed; in that case only
36 the selected packets will be written to the capture file.
37 Editcap can also be used to remove duplicate packets. Several
39 different options (-d, -D and -w) are used to control the packet window
40 or relative time window to be used for duplicate comparison.
41 Editcap can be used to assign comment strings to frame numbers.
43 Editcap is able to detect, read and write the same capture files that
45 are supported by Wireshark. The input file doesn't need a specific
46 filename extension; the file format and an optional gzip compression
47 will be automatically detected. Near the beginning of the DESCRIPTION
48 section of wireshark(1) or
49 <https://www.wireshark.org/docs/man-pages/wireshark.html> is a detailed
50 description of the way Wireshark handles this, which is the same way
51 Editcap handles this.
52 Editcap can write the file in several output formats. The -F flag can
54 be used to specify the format in which to write the capture file;
55 editcap -F provides a list of the available output formats.
56
58 -a <framenum:comment>
59 For the specificed frame number, assign the given comment string.
60 Can be repeated for multiple frames. Quotes should be used with
61 comment strings that include spaces.
62 -A <start time>
64 Saves only the packets whose timestamp is on or after start time.
65 The time is given in the following format YYYY-MM-DD HH:MM:SS
66 -B <stop time>
68 Saves only the packets whose timestamp is before stop time. The
69 time is given in the following format YYYY-MM-DD HH:MM:SS
70 -c <packets per file>
72 Splits the packet output to different files based on uniform packet
73 counts with a maximum of <packets per file> each. Each output file
74 will be created with a suffix -nnnnn, starting with 00000. If the
75 specified number of packets is written to the output file, the next
76 output file is opened. The default is to use a single output file.
77 -C [offset:]<choplen>
79 Sets the chop length to use when writing the packet data. Each
80 packet is chopped by <choplen> bytes of data. Positive values chop
81 at the packet beginning while negative values chop at the packet
82 end.
83 If an optional offset precedes the <choplen>, then the bytes
85 chopped will be offset from that value. Positive offsets are from
86 the packet beginning, while negative offsets are from the packet
87 end.
88 This is useful for chopping headers for decapsulation of an entire
90 capture, removing tunneling headers, or in the rare case that the
91 conversion between two file formats leaves some random bytes at the
92 end of each packet. Another use is for removing vlan tags.
93 NOTE: This option can be used more than once, effectively allowing
95 you to chop bytes from up to two different areas of a packet in a
96 single pass provided that you specify at least one chop length as a
97 positive value and at least one as a negative value. All positive
98 chop lengths are added together as are all negative chop lengths.
99 -d Attempts to remove duplicate packets. The length and MD5 hash of
101 the current packet are compared to the previous four (4) packets.
102 If a match is found, the current packet is skipped. This option is
103 equivalent to using the option -D 5.
104 -D <dup window>
106 Attempts to remove duplicate packets. The length and MD5 hash of
107 the current packet are compared to the previous <dup window> - 1
108 packets. If a match is found, the current packet is skipped.
109 The use of the option -D 0 combined with the -v option is useful in
111 that each packet's Packet number, Len and MD5 Hash will be printed
112 to standard out. This verbose output (specifically the MD5 hash
113 strings) can be useful in scripts to identify duplicate packets
114 across trace files.
115 The <dup window> is specified as an integer value between 0 and
117 1000000 (inclusive).
118 NOTE: Specifying large <dup window> values with large tracefiles
120 can result in very long processing times for editcap.
121 -E <error probability>
123 Sets the probability that bytes in the output file are randomly
124 changed. Editcap uses that probability (between 0.0 and 1.0
125 inclusive) to apply errors to each data byte in the file. For
126 instance, a probability of 0.02 means that each byte has a 2%
127 chance of having an error.
128 This option is meant to be used for fuzz-testing protocol
130 dissectors.
131 -F <file format>
133 Sets the file format of the output capture file. Editcap can write
134 the file in several formats, editcap -F provides a list of the
135 available output formats. The default is the pcap format.
136 -h Prints the version and options and exits.
138 -i <seconds per file>
140 Splits the packet output to different files based on uniform time
141 intervals using a maximum interval of <seconds per file> each. Each
142 output file will be created with a suffix -nnnnn, starting with
143 00000. If packets for the specified time interval are written to
144 the output file, the next output file is opened. The default is to
145 use a single output file.
146 -I <bytes to ignore>
148 Ignore the specified number of bytes at the beginning of the frame
149 during MD5 hash calculation, unless the frame is too short, then
150 the full frame is used. Useful to remove duplicated packets taken
151 on several routers (different mac addresses for example) e.g. -I 26
152 in case of Ether/IP will ignore ether(14) and IP header(20 - 4(src
153 ip) - 4(dst ip)). The default value is 0.
154 -L Adjust the original frame length accordingly when chopping and/or
156 snapping (in addition to the captured length, which is always
157 adjusted regardless of whether -L is specified or not). See also
158 -C <choplen> and -s <snaplen>.
159 -o <change offset>
161 When used in conjunction with -E, skip some bytes from the
162 beginning of the packet from being changed. In this way some
163 headers don't get changed, and the fuzzer is more focused on a
164 smaller part of the packet. Keeping a part of the packet fixed the
165 same dissector is triggered, that make the fuzzing more precise.
166 -r Reverse the packet selection. Causes the packets whose packet
168 numbers are specified on the command line to be written to the
169 output capture file, instead of discarding them.
170 -s <snaplen>
172 Sets the snapshot length to use when writing the data. If the -s
173 flag is used to specify a snapshot length, packets in the input
174 file with more captured data than the specified snapshot length
175 will have only the amount of data specified by the snapshot length
176 written to the output file.
177 This may be useful if the program that is to read the output file
179 cannot handle packets larger than a certain size (for example, the
180 versions of snoop in Solaris 2.5.1 and Solaris 2.6 appear to reject
181 Ethernet packets larger than the standard Ethernet MTU, making them
182 incapable of handling gigabit Ethernet captures if jumbo packets
183 were used).
184 -S <strict time adjustment>
186 Time adjust selected packets to ensure strict chronological order.
187 The <strict time adjustment> value represents relative seconds
189 specified as [-]seconds[.fractional seconds].
190 As the capture file is processed each packet's absolute time is
192 possibly adjusted to be equal to or greater than the previous
193 packet's absolute timestamp depending on the <strict time
194 adjustment> value.
195 If <strict time adjustment> value is 0 or greater (e.g. 0.000001)
197 then only packets with a timestamp less than the previous packet
198 will adjusted. The adjusted timestamp value will be set to be
199 equal to the timestamp value of the previous packet plus the value
200 of the <strict time adjustment> value. A <strict time adjustment>
201 value of 0 will adjust the minimum number of timestamp values
202 necessary to ensure that the resulting capture file is in strict
203 chronological order.
204 If <strict time adjustment> value is specified as a negative value,
206 then the timestamp values of all packets will be adjusted to be
207 equal to the timestamp value of the previous packet plus the
208 absolute value of the <lt>strict time adjustment<gt> value. A
209 <strict time adjustment> value of -0 will result in all packets
210 having the timestamp value of the first packet.
211 This feature is useful when the trace file has an occasional packet
213 with a negative delta time relative to the previous packet.
214 -t <time adjustment>
216 Sets the time adjustment to use on selected packets. If the -t
217 flag is used to specify a time adjustment, the specified adjustment
218 will be applied to all selected packets in the capture file. The
219 adjustment is specified as [-]seconds[.fractional seconds]. For
220 example, -t 3600 advances the timestamp on selected packets by one
221 hour while -t -0.5 reduces the timestamp on selected packets by
222 one-half second.
223 This feature is useful when synchronizing dumps collected on
225 different machines where the time difference between the two
226 machines is known or can be estimated.
227 -T <encapsulation type>
229 Sets the packet encapsulation type of the output capture file. If
230 the -T flag is used to specify an encapsulation type, the
231 encapsulation type of the output capture file will be forced to the
232 specified type. editcap -T provides a list of the available types.
233 The default type is the one appropriate to the encapsulation type
234 of the input capture file.
235 Note: this merely forces the encapsulation type of the output file
237 to be the specified type; the packet headers of the packets will
238 not be translated from the encapsulation type of the input capture
239 file to the specified encapsulation type (for example, it will not
240 translate an Ethernet capture to an FDDI capture if an Ethernet
241 capture is read and '-T fddi' is specified). If you need to
242 remove/add headers from/to a packet, you will need
243 od(1)/text2pcap(1).
244 -v Causes editcap to print verbose messages while it's working.
246 Use of -v with the de-duplication switches of -d, -D or -w will
248 cause all MD5 hashes to be printed whether the packet is skipped or
249 not.
250 -V Print the version and exit.
252 -w <dup time window>
254 Attempts to remove duplicate packets. The current packet's arrival
255 time is compared with up to 1000000 previous packets. If the
256 packet's relative arrival time is less than or equal to the <dup
257 time window> of a previous packet and the packet length and MD5
258 hash of the current packet are the same then the packet to skipped.
259 The duplicate comparison test stops when the current packet's
260 relative arrival time is greater than <dup time window>.
261 The <dup time window> is specified as seconds[.fractional seconds].
263 The [.fractional seconds] component can be specified to nine (9)
265 decimal places (billionths of a second) but most typical trace
266 files have resolution to six (6) decimal places (millionths of a
267 second).
268 NOTE: Specifying large <dup time window> values with large
270 tracefiles can result in very long processing times for editcap.
271 NOTE: The -w option assumes that the packets are in chronological
273 order. If the packets are NOT in chronological order then the -w
274 duplication removal option may not identify some duplicates.
275
277 To see more detailed description of the options use:
278 editcap -h
280 To shrink the capture file by truncating the packets at 64 bytes and
282 writing it as Sun snoop file use:
283 editcap -s 64 -F snoop capture.pcap shortcapture.snoop
285 To delete packet 1000 from the capture file use:
287 editcap capture.pcap sans1000.pcap 1000
289 To limit a capture file to packets from number 200 to 750 (inclusive)
291 use:
292 editcap -r capture.pcap small.pcap 200-750
294 To get all packets from number 1-500 (inclusive) use:
296 editcap -r capture.pcap first500.pcap 1-500
298 or
300 editcap capture.pcap first500.pcap 501-9999999
302 To exclude packets 1, 5, 10 to 20 and 30 to 40 from the new file use:
304 editcap capture.pcap exclude.pcap 1 5 10-20 30-40
306 To select just packets 1, 5, 10 to 20 and 30 to 40 for the new file
308 use:
309 editcap -r capture.pcap select.pcap 1 5 10-20 30-40
311 To remove duplicate packets seen within the prior four frames use:
313 editcap -d capture.pcap dedup.pcap
315 To remove duplicate packets seen within the prior 100 frames use:
317 editcap -D 101 capture.pcap dedup.pcap
319 To remove duplicate packets seen equal to or less than 1/10th of a
321 second:
322 editcap -w 0.1 capture.pcap dedup.pcap
324 To display the MD5 hash for all of the packets (and NOT generate any
326 real output file):
327 editcap -v -D 0 capture.pcap /dev/null
329 or on Windows systems
331 editcap -v -D 0 capture.pcap NUL
333 To advance the timestamps of each packet forward by 3.0827 seconds:
335 editcap -t 3.0827 capture.pcap adjusted.pcap
337 To ensure all timestamps are in strict chronological order:
339 editcap -S 0 capture.pcap adjusted.pcap
341 To introduce 5% random errors in a capture file use:
343 editcap -E 0.05 capture.pcap capture_error.pcap
345 To remove vlan tags from all packets within an Ethernet-encapsulated
347 capture file, use:
348 editcap -L -C 12:4 capture_vlan.pcap capture_no_vlan.pcap
350 To chop both the 10 byte and 20 byte regions from the following 75 byte
352 packet in a single pass, use any of the 8 possible methods provided
353 below:
354 <--------------------------- 75 ---------------------------->
356 +---+-------+-----------+---------------+-------------------+
358 | 5 | 10 | 15 | 20 | 25 |
359 +---+-------+-----------+---------------+-------------------+
360 1) editcap -C 5:10 -C -25:-20 capture.pcap chopped.pcap
362 2) editcap -C 5:10 -C 50:-20 capture.pcap chopped.pcap
363 3) editcap -C -70:10 -C -25:-20 capture.pcap chopped.pcap
364 4) editcap -C -70:10 -C 50:-20 capture.pcap chopped.pcap
365 5) editcap -C 30:20 -C -60:-10 capture.pcap chopped.pcap
366 6) editcap -C 30:20 -C 15:-10 capture.pcap chopped.pcap
367 7) editcap -C -45:20 -C -60:-10 capture.pcap chopped.pcap
368 8) editcap -C -45:20 -C 15:-10 capture.pcap chopped.pcap
369 To add comment strings to the first 2 input frames, use:
371 editcap -a "1:1st frame" -a 2:Second capture.pcap capture-comments.pcap
373
375 pcap(3), wireshark(1), tshark(1), mergecap(1), dumpcap(1), capinfos(1),
376 text2pcap(1), od(1), pcap-filter(7) or tcpdump(8)
377
379 Editcap is part of the Wireshark distribution. The latest version of
380 Wireshark can be found at <https://www.wireshark.org>.
381 HTML versions of the Wireshark project man pages are available at:
383 <https://www.wireshark.org/docs/man-pages>.
384
386 Original Author
387 -------- ------
388 Richard Sharpe <sharpe[AT]ns.aus.com>
389 Contributors
392 ------------
393 Guy Harris <guy[AT]alum.mit.edu>
394 Ulf Lamping <ulf.lamping[AT]web.de>
3952.6.2 2018-07-18 EDITCAP(1)