1EDITCAP(1) 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> ]
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 ]
15 [ --inject-secrets <secrets type>,<file> ] [ --discard-all-secrets ]
16 [ --capture-comment <comment> ] [ --discard-capture-comment ] infile
17 outfile [ packet#[-packet#] ... ]
18 editcap -d -D <dup window> -w <dup time window> [ -V ]
20 [ -I <bytes to ignore> ] [ --skip-radiotap-header ] infile outfile
21 editcap -h|--help
23 editcap -v|--version
25
27 Editcap is a program that reads some or all of the captured packets
28 from the infile, optionally converts them in various ways and writes
29 the resulting packets to the capture outfile (or outfiles).
30 By default, it reads all packets from the infile and writes them to the
32 outfile in pcapng file format. Use '-' for infile or outfile to read
33 from standard input or write to standard output, respectively.
34 The -A and -B option allow you to limit the time range from which
36 packets are read from the infile.
37 An optional list of packet numbers can be specified on the command
39 tail; individual packet numbers separated by whitespace and/or ranges
40 of packet numbers can be specified as start-end, referring to all
41 packets from start to end. By default the selected packets with those
42 numbers will not be written to the capture file. If the -r flag is
43 specified, the whole packet selection is reversed; in that case only
44 the selected packets will be written to the capture file.
45 Editcap can also be used to remove duplicate packets. Several different
47 options (-d, -D and -w) are used to control the packet window or
48 relative time window to be used for duplicate comparison.
49 Editcap can be used to assign comment strings to frame numbers.
51 Editcap is able to detect, read and write the same capture files that
53 are supported by Wireshark. The input file doesn’t need a specific
54 filename extension; the file format and an optional gzip, zstd or lz4
55 compression will be automatically detected. Near the beginning of the
56 DESCRIPTION section of wireshark(1) or
57 https://www.wireshark.org/docs/man-pages/wireshark.html is a detailed
58 description of the way Wireshark handles this, which is the same way
59 Editcap handles this.
60 Editcap can write the file in several output formats. The -F flag can
62 be used to specify the format in which to write the capture file;
63 editcap -F provides a list of the available output formats.
64
66 -a <framenum:comment>
67 For the specified frame number, assign the given comment string.
69 Can be repeated for multiple frames. Quotes should be used with
70 comment strings that include spaces.
71 -A <start time>
73 Reads only the packets whose timestamp is on or after start time.
75 The time is given in ISO 8601 format, either YYYY-MM-DD
76 HH:MM:SS[.nnnnnnnnn][Z|±hh:mm] or
77 YYYY-MM-DDTHH:MM:SS[.nnnnnnnnn][Z|±hh:mm] . The fractional seconds
78 are optional, as is the time zone offset from UTC (in which case
79 local time is assumed). Unix epoch timestamps (floating point
80 format) are also accepted.
81 -B <stop time>
83 Reads only the packets whose timestamp is before stop time. The
85 time is given in ISO 8601 format, either YYYY-MM-DD
86 HH:MM:SS[.nnnnnnnnn][Z|±hh:mm] or
87 YYYY-MM-DDTHH:MM:SS[.nnnnnnnnn][Z|±hh:mm] . The fractional seconds
88 are optional, as is the time zone offset from UTC (in which case
89 local time is assumed). Unix epoch timestamps (floating point
90 format) are also accepted.
91 -c <packets per file>
93 Splits the packet output to different files based on uniform packet
95 counts with a maximum of <packets per file> each.
96 Each output file will be created with an infix
98 _nnnnn[_YYYYmmddHHMMSS] inserted before the file extension (which
99 may be null) of outfile. The infix consists of the ordinal number
100 of the output file, starting with 00000, followed by the timestamp
101 of its first packet. The timestamp is omitted if the input file
102 does not contain timestamp information.
103 After the specified number of packets is written to the output
105 file, the next output file is opened. The default is to use a
106 single output file. This option conflicts with -i.
107 -C [offset:]<choplen>
109 Sets the chop length to use when writing the packet data. Each
111 packet is chopped by <choplen> bytes of data. Positive values chop
112 at the packet beginning while negative values chop at the packet
113 end.
114 If an optional offset precedes the <choplen>, then the bytes
116 chopped will be offset from that value. Positive offsets are from
117 the packet beginning, while negative offsets are from the packet
118 end.
119 This is useful for chopping headers for decapsulation of an entire
121 capture, removing tunneling headers, or in the rare case that the
122 conversion between two file formats leaves some random bytes at the
123 end of each packet. Another use is for removing vlan tags.
124 Note
126 This option can be used more than once, effectively allowing
127 you to chop bytes from up to two different areas of a packet in
128 a single pass provided that you specify at least one chop
129 length as a positive value and at least one as a negative
130 value. All positive chop lengths are added together as are all
131 negative chop lengths.
132 -d
134 Attempts to remove duplicate packets. The length and MD5 hash of
136 the current packet are compared to the previous four (4) packets.
137 If a match is found, the current packet is skipped. This option is
138 equivalent to using the option -D 5.
139 -D <dup window>
141 Attempts to remove duplicate packets. The length and MD5 hash of
143 the current packet are compared to the previous <dup window> - 1
144 packets. If a match is found, the current packet is skipped.
145 The use of the option -D 0 combined with the -V option is useful in
147 that each packet’s Packet number, Len and MD5 Hash will be printed
148 to standard error. This verbose output (specifically the MD5 hash
149 strings) can be useful in scripts to identify duplicate packets
150 across trace files.
151 The <dup window> is specified as an integer value between 0 and
153 1000000 (inclusive).
154 Note
156 Specifying large <dup window> values with large tracefiles can
157 result in very long processing times for editcap.
158 -E <error probability>
160 Sets the probability that bytes in the output file are randomly
162 changed. Editcap uses that probability (between 0.0 and 1.0
163 inclusive) to apply errors to each data byte in the file. For
164 instance, a probability of 0.02 means that each byte has a 2%
165 chance of having an error.
166 This option is meant to be used for fuzz-testing protocol
168 dissectors.
169 -F <file format>
171 Sets the file format of the output capture file. Editcap can write
173 the file in several formats, editcap -F provides a list of the
174 available output formats. The default is the pcapng format.
175 -h|--help
177 Prints the version and options and exits.
179 -i <seconds per file>
181 Splits the packet output to different files based on uniform time
183 intervals using a maximum interval of <seconds per file> each.
184 Floating point values (e.g. 0.5) are allowed.
185 Each output file will be created with an infix
187 _nnnnn[_YYYYmmddHHMMSS] inserted before the file extension (which
188 may be null) of outfile. The infix consists of the ordinal number
189 of the output file, starting with 00000, followed by the timestamp
190 of its first packet. The timestamp is omitted if the input file
191 does not contain timestamp information.
192 After packets for the specified time interval are written to the
194 output file, the next output file is opened. The default is to use
195 a single output file. This option conflicts with -c.
196 -I <bytes to ignore>
198 Ignore the specified number of bytes at the beginning of the frame
200 during MD5 hash calculation, unless the frame is too short, then
201 the full frame is used. Useful to remove duplicated packets taken
202 on several routers (different mac addresses for example) e.g. -I 26
203 in case of Ether/IP will ignore ether(14) and IP header(20 - 4(src
204 ip) - 4(dst ip)). The default value is 0.
205 -L
207 Adjust the original frame length accordingly when chopping and/or
209 snapping (in addition to the captured length, which is always
210 adjusted regardless of whether -L is specified or not). See also -C
211 <choplen> and -s <snaplen>.
212 -o <change offset>
214 When used in conjunction with -E, skip some bytes from the
216 beginning of the packet from being changed. In this way some
217 headers don’t get changed, and the fuzzer is more focused on a
218 smaller part of the packet. Keeping a part of the packet fixed the
219 same dissector is triggered, that make the fuzzing more precise.
220 -r
222 Reverse the packet selection. Causes the packets whose packet
224 numbers are specified on the command line to be written to the
225 output capture file, instead of discarding them.
226 -s <snaplen>
228 Sets the snapshot length to use when writing the data. If the -s
230 flag is used to specify a snapshot length, packets in the input
231 file with more captured data than the specified snapshot length
232 will have only the amount of data specified by the snapshot length
233 written to the output file.
234 This may be useful if the program that is to read the output file
236 cannot handle packets larger than a certain size (for example, the
237 versions of snoop in Solaris 2.5.1 and Solaris 2.6 appear to reject
238 Ethernet packets larger than the standard Ethernet MTU, making them
239 incapable of handling gigabit Ethernet captures if jumbo packets
240 were used).
241 --seed <seed>
243 When used in conjunction with -E, set the seed for the
245 pseudo-random number generator. This is useful for recreating a
246 particular sequence of errors.
247 --skip-radiotap-header
249 Skip the radiotap header of each frame when checking for packet
251 duplicates. This is useful when processing a capture created by
252 combining outputs of multiple capture devices on the same channel
253 in the vicinity of each other.
254 -S <strict time adjustment>
256 Time adjust selected packets to ensure strict chronological order.
258 The <strict time adjustment> value represents relative seconds
260 specified as seconds[.fractional seconds].
261 As the capture file is processed each packet’s absolute time is
263 possibly adjusted to be equal to or greater than the previous
264 packet’s absolute timestamp depending on the <strict time
265 adjustment> value.
266 If <strict time adjustment> value is 0 or greater (e.g. 0.000001)
268 then only packets with a timestamp less than the previous packet
269 will adjusted. The adjusted timestamp value will be set to be equal
270 to the timestamp value of the previous packet plus the value of the
271 <strict time adjustment> value. A <strict time adjustment> value of
272 0 will adjust the minimum number of timestamp values necessary to
273 ensure that the resulting capture file is in strict chronological
274 order.
275 If <strict time adjustment> value is specified as a negative value,
277 then the timestamp values of all packets will be adjusted to be
278 equal to the timestamp value of the previous packet plus the
279 absolute value of the <strict time adjustment> value. A <strict
280 time adjustment> value of -0 will result in all packets having the
281 timestamp value of the first packet.
282 This feature is useful when the trace file has an occasional packet
284 with a negative delta time relative to the previous packet.
285 -t <time adjustment>
287 Sets the time adjustment to use on selected packets. If the -t flag
289 is used to specify a time adjustment, the specified adjustment will
290 be applied to all selected packets in the capture file. The
291 adjustment is specified as seconds[.fractional seconds]. For
292 example, -t 3600 advances the timestamp on selected packets by one
293 hour while -t -0.5 reduces the timestamp on selected packets by
294 one-half second.
295 This feature is useful when synchronizing dumps collected on
297 different machines where the time difference between the two
298 machines is known or can be estimated.
299 -T <encapsulation type>
301 Sets the packet encapsulation type of the output capture file. If
303 the -T flag is used to specify an encapsulation type, the
304 encapsulation type of the output capture file will be forced to the
305 specified type. editcap -T provides a list of the available types.
306 The default type is the one appropriate to the encapsulation type
307 of the input capture file.
308 Note: this merely forces the encapsulation type of the output file
310 to be the specified type; the packet headers of the packets will
311 not be translated from the encapsulation type of the input capture
312 file to the specified encapsulation type (for example, it will not
313 translate an Ethernet capture to an FDDI capture if an Ethernet
314 capture is read and '-T fddi' is specified). If you need to
315 remove/add headers from/to a packet, you will need
316 od(1)/text2pcap(1).
317 -v|--version
319 Print the version and exit.
321 -V
323 Causes editcap to print verbose messages while it’s working.
325 Use of -V with the de-duplication switches of -d, -D or -w will
327 cause all MD5 hashes to be printed whether the packet is skipped or
328 not.
329 -w <dup time window>
331 Attempts to remove duplicate packets. The current packet’s arrival
333 time is compared with up to 1000000 previous packets. If the
334 packet’s relative arrival time is less than or equal to the <dup
335 time window> of a previous packet and the packet length and MD5
336 hash of the current packet are the same then the packet to skipped.
337 The duplicate comparison test stops when the current packet’s
338 relative arrival time is greater than <dup time window>.
339 The <dup time window> is specified as seconds[.fractional seconds].
341 The [.fractional seconds] component can be specified to nine (9)
343 decimal places (billionths of a second) but most typical trace
344 files have resolution to six (6) decimal places (millionths of a
345 second).
346 Note
348 Specifying large <dup time window> values with large tracefiles
349 can result in very long processing times for editcap.
350 Note
352 The -w option assumes that the packets are in chronological
353 order. If the packets are NOT in chronological order then the
354 -w duplication removal option may not identify some duplicates.
355 --inject-secrets <secrets type>,<file>
357 Inserts the contents of <file> into a Decryption Secrets Block
359 (DSB) within the pcapng output file. This enables decryption
360 without requiring additional configuration in protocol preferences.
361 The file format is described by <secrets type> which can be one of:
363 tls TLS Key Log as described at
365 https://developer.mozilla.org/NSS_Key_Log_Format wg WireGuard Key
366 Log, see
367 https://gitlab.com/wireshark/wireshark/-/wikis/WireGuard#key-log-format
368 This option may be specified multiple times. The available options
370 for <secrets type> can be listed with --inject-secrets help.
371 --discard-all-secrets
373 Discard all decryption secrets from the input file when writing the
375 output file. Does not discard secrets added by --inject-secrets in
376 the same command line.
377 --capture-comment <comment>
379 Adds the given comment to the output file, if supported by the
381 output file format. New comments will be added after any comments
382 present in the input file unless --discard-capture-comment is also
383 specified.
384 This option may be specified multiple times. Note that Wireshark
386 currently only displays the first comment of a capture file.
387 --discard-capture-comment
389 Discard all capture file comments from the input file when writing
391 the output file. Does not discard comments added by
392 --capture-comment in the same command line.
393
395 --log-level <level>
396 Set the active log level. Supported levels in lowest to highest
397 order are "noisy", "debug", "info", "message", "warning",
398 "critical", and "error". Messages at each level and higher will be
399 printed, for example "warning" prints "warning", "critical", and
400 "error" messages and "noisy" prints all messages. Levels are case
401 insensitive.
402 --log-fatal <level>
404 Abort the program if any messages are logged at the specified level
405 or higher. For example, "warning" aborts on any "warning",
406 "critical", or "error" messages.
407 --log-domains <list>
409 Only print messages for the specified log domains, e.g.
410 "GUI,Epan,sshdump". List of domains must be comma-separated.
411 --log-debug <list>
413 Force the specified domains to log at the "debug" level. List of
414 domains must be comma-separated.
415 --log-noisy <list>
417 Force the specified domains to log at the "noisy" level. List of
418 domains must be comma-separated.
419 --log-file <path>
421 Write log messages and stderr output to the specified file.
422
424 To see more detailed description of the options use:
425 editcap -h
427 To shrink the capture file by truncating the packets at 64 bytes and
429 writing it as Sun snoop file use:
430 editcap -s 64 -F snoop capture.pcapng shortcapture.snoop
432 To delete packet 1000 from the capture file use:
434 editcap capture.pcapng sans1000.pcapng 1000
436 To limit a capture file to packets from number 200 to 750 (inclusive)
438 use:
439 editcap -r capture.pcapng small.pcapng 200-750
441 To get all packets from number 1-500 (inclusive) use:
443 editcap -r capture.pcapng first500.pcapng 1-500
445 or
447 editcap capture.pcapng first500.pcapng 501-9999999
449 To exclude packets 1, 5, 10 to 20 and 30 to 40 from the new file use:
451 editcap capture.pcapng exclude.pcapng 1 5 10-20 30-40
453 To select just packets 1, 5, 10 to 20 and 30 to 40 for the new file
455 use:
456 editcap -r capture.pcapng select.pcapng 1 5 10-20 30-40
458 To remove duplicate packets seen within the prior four frames use:
460 editcap -d capture.pcapng dedup.pcapng
462 To remove duplicate packets seen within the prior four frames while
464 skipping radiotap headers use:
465 editcap -d --skip-radiotap-header capture.pcapng dedup.pcapng
467 To remove duplicate packets seen within the prior 100 frames use:
469 editcap -D 101 capture.pcapng dedup.pcapng
471 To remove duplicate packets seen equal to or less than 1/10th of a
473 second:
474 editcap -w 0.1 capture.pcapng dedup.pcapng
476 To display the MD5 hash for all of the packets (and NOT generate any
478 real output file):
479 editcap -V -D 0 capture.pcapng /dev/null
481 or on Windows systems
483 editcap -V -D 0 capture.pcapng NUL
485 To advance the timestamps of each packet forward by 3.0827 seconds:
487 editcap -t 3.0827 capture.pcapng adjusted.pcapng
489 To ensure all timestamps are in strict chronological order:
491 editcap -S 0 capture.pcapng adjusted.pcapng
493 To introduce 5% random errors in a capture file use:
495 editcap -E 0.05 capture.pcapng capture_error.pcapng
497 To remove vlan tags from all packets within an Ethernet-encapsulated
499 capture file, use:
500 editcap -L -C 12:4 capture_vlan.pcapng capture_no_vlan.pcapng
502 To chop both the 10 byte and 20 byte regions from the following 75 byte
504 packet in a single pass, use any of the 8 possible methods provided
505 below:
506 <--------------------------- 75 ---------------------------->
508 +---+-------+-----------+---------------+-------------------+
510 | 5 | 10 | 15 | 20 | 25 |
511 +---+-------+-----------+---------------+-------------------+
512 1) editcap -C 5:10 -C -25:-20 capture.pcapng chopped.pcapng
514 2) editcap -C 5:10 -C 50:-20 capture.pcapng chopped.pcapng
515 3) editcap -C -70:10 -C -25:-20 capture.pcapng chopped.pcapng
516 4) editcap -C -70:10 -C 50:-20 capture.pcapng chopped.pcapng
517 5) editcap -C 30:20 -C -60:-10 capture.pcapng chopped.pcapng
518 6) editcap -C 30:20 -C 15:-10 capture.pcapng chopped.pcapng
519 7) editcap -C -45:20 -C -60:-10 capture.pcapng chopped.pcapng
520 8) editcap -C -45:20 -C 15:-10 capture.pcapng chopped.pcapng
521 To add comment strings to the first 2 input frames, use:
523 editcap -a "1:1st frame" -a 2:Second capture.pcapng capture-comments.pcapng
525
527 pcap(3), wireshark(1), tshark(1), mergecap(1), dumpcap(1), capinfos(1),
528 text2pcap(1), reordercap(1), od(1), pcap-filter(7) or tcpdump(8)
529
531 This is the manual page for Editcap 4.0.8. Editcap is part of the
532 Wireshark distribution. The latest version of Wireshark can be found at
533 https://www.wireshark.org.
534 HTML versions of the Wireshark project man pages are available at
536 https://www.wireshark.org/docs/man-pages.
537
539 Original Author
540 Richard Sharpe <sharpe[AT]ns.aus.com>
541 Contributors
543 Guy Harris <guy[AT]alum.mit.edu>
544 Ulf Lamping <ulf.lamping[AT]web.de>
545 2023-08-31 EDITCAP(1)