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TCPSLICE(8)									      TCPSLICE(8)

       tcpslice - extract pieces of and/or glue together tcpdump files

       tcpslice [ -dRrt ] [ -w file ]
		[ start-time [ end-time ] ] file ...

       Tcpslice  is  a program for extracting portions of packet-trace files generated using tcp-
       dump(1)'s -w flag.  It can also be used to glue together several such files, as	discussed

       The  basic  operation  of tcpslice is to copy to stdout all packets from its input file(s)
       whose timestamps fall within a given range.  The starting and ending times  of  the  range
       may  be	specified  on  the  command  line.   All ranges are inclusive.	The starting time
       defaults to the time of the first packet in the first input file; we call this  the  first
       time.   The  ending time defaults to ten years after the starting time.	Thus, the command
       tcpslice trace-file simply copies trace-file to stdout (assuming the file does not include
       more than ten years' worth of data).

       There  are  a  number of ways to specify times.	The first is using Unix timestamps of the
       form sssssssss.uuuuuu (this is the format specified by tcpdump's -tt flag).  For  example,
       654321098.7654  specifies  38 seconds and 765,400 microseconds after 8:51PM PDT, Sept. 25,

       All examples in this manual are given for PDT times, but when displaying times and  inter-
       preting	times  symbolically as discussed below, tcpslice uses the local timezone, regard-
       less of the timezone in which the tcpdump file was generated.  The  daylight-savings  set-
       ting  used  is  that  which is appropriate for the local timezone at the date in question.
       For example, times associated with summer months  will  usually	include  daylight-savings
       effects, and those with winter months will not.

       Times  may also be specified relative to either the first time (when specifying a starting
       time) or the starting time (when specifying an ending time) by preceding a  numeric  value
       in  seconds  with a `+'.  For example, a starting time of +200 indicates 200 seconds after
       the first time, and the two arguments +200 +300 indicate from 200 seconds after the  first
       time through 500 seconds after the first time.

       Times  may  also be specified in terms of years (y), months (m), days (d), hours (h), min-
       utes  (m),  seconds  (s),  and  microseconds(u).   For	example,   the	 Unix	timestamp
       654321098.7654 discussed above could also be expressed as 90y9m25d20h51m38s765400u.

       When  specifying  times	using this style, fields that are omitted default as follows.  If
       the omitted field is a unit greater than that of the first specified field, then its value
       defaults  to the corresponding value taken from either first time (if the starting time is
       being specified) or the starting time (if the ending time is  being  specified).   If  the
       omitted	field  is a unit less than that of the first specified field, then it defaults to
       zero.  For example, suppose that the input file has a first time  of  the  Unix	timestamp
       mentioned  above,  i.e.,  38  seconds and 765,400 microseconds after 8:51PM PDT, Sept. 25,
       1990.  To specify 9:36PM PDT (exactly) on the same date we could use 21h36m.  To specify a
       range from 9:36PM PDT through 1:54AM PDT the next day we could use 21h36m 26d1h54m.

       Relative  times	can also be specified when using the ymdhmsu format.  Omitted fields then
       default to 0 if the unit of the field is greater than that of the first	specified  field,
       and  to	the  corresponding value taken from either the first time or the starting time if
       the omitted field's unit is less than that of the first specified field.   Given  a  first
       time  of the Unix timestamp mentioned above, 22h +1h10m specifies a range from 10:00PM PDT
       on that date through 11:10PM PDT, and +1h +1h10m specifies a range  from  38.7654  seconds
       after  9:51PM  PDT  through 38.7654 seconds after 11:01PM PDT.  The first hour of the file
       could be extracted using +0 +1h.

       Note that with the ymdhmsu format there is an ambiguity between using m for `month' or for
       `minute'.   The	ambiguity  is resolved as follows: if an m field is followed by a d field
       then it is interpreted as specifying months; otherwise it specifies minutes.

       If more than one input file is specified then tcpslice first copies packets lying  in  the
       given  range  from the first file; it then increases the starting time of the range to lie
       just beyond the timestamp of the last packet in the first file, repeats the  process  with
       the  second  file,  and so on.  Thus files with interleaved packets are not merged.  For a
       given file, only packets that are newer than any in the preceding files	will  be  consid-
       ered.   This  mechanism avoids any possibility of a packet occurring more than once in the

       If any of -R, -r or -t are specified then tcpslice reports the timestamps of the first and
       last  packets in each input file and exits.  Only one of these three options may be speci-

       -d     Dump the start and end times specified by the given range and exit.  This option is
	      useful  for checking that the given range actually specifies the times you think it
	      does.  If one of -R, -r or -t has been specified then the times are dumped  in  the
	      corresponding format; otherwise, raw format ( -R) is used.

       -R     Dump  the  timestamps of the first and last packets in each input file as raw time-
	      stamps (i.e., in the form  sssssssss.uuuuuu).

       -r     Same as -R except the timestamps are dumped in human-readable  format,  similar  to
	      that used by  date(1).

       -t     Same  as	-R  except  the  timestamps  are  dumped in tcpslice format, i.e., in the
	      ymdhmsu format discussed above.

       -w     Direct the output to file rather than stdout.


       The original author was:

       Vern Paxson, of Lawrence Berkeley Laboratory, University of California, Berkeley, CA.

       It is currently being maintained by tcpdump.org.

       The current version is available in the ``tcpslice''  module  of  the  CVS  tree  at  tcp-
       dump.org; see the tcpdump.org home page at


       for information on anonymous CVS access.

       The original distribution is available via anonymous ftp:


       Please send problems, bugs, questions, desirable enhancements, etc. to:


       Please send source code contributions, etc. to:


       An input filename that beings with a digit or a `+' can be confused with a start/end time.
       Such filenames can be specified with  a	leading  `./';	for  example,  specify	the  file
       `04Jul76.trace' as `./04Jul76.trace'.

       tcpslice  cannot read its input from stdin, since it uses random-access to rummage through
       its input files.

       tcpslice refuses to write to its output if it is a terminal (as indicated  by  isatty(3)).
       This  is  not  a  bug but a feature, to prevent it from spraying binary data to the user's
       terminal.  Note that this means you must either redirect stdout or specify an output  file
       via -w.

       tcpslice  will  not work properly on tcpdump files spanning more than one year; with files
       containing portions of packets whose original length was more than 65,535 bytes; nor  with
       files  containing  fewer  than  three  packets.	 Such  files result in the error message:
       `couldn't find final packet in file'.  These problems are due to the interpolation  scheme
       used  by  tcpslice to greatly speed up its processing when dealing with large trace files.
       Note that tcpslice can efficiently extract slices from the middle of trace  files  of  any
       size,  and can also work with truncated trace files (i.e., the final packet in the file is
       only partially present, typically due to tcpdump being ungracefully killed).

					 21 December 1996			      TCPSLICE(8)
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