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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 20:34:10 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 20:34:10 +0000
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Adding upstream version 4.2.2.upstream/4.2.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+include::../docbook/attributes.adoc[]
+= mergecap(1)
+:doctype: manpage
+:stylesheet: ws.css
+:linkcss:
+:copycss: ../docbook/{stylesheet}
+
+== NAME
+
+mergecap - Merges two or more capture files into one
+
+== SYNOPSIS
+
+[manarg]
+*mergecap*
+[ *-a* ]
+[ *-F* <__file format__> ]
+[ *-I* <__IDB merge mode__> ]
+[ *-s* <__snaplen__> ]
+[ *-V* ]
+*-w* <__outfile__>|-
+<__infile__> [<__infile__> __...__]
+
+[manarg]
+*mergecap*
+*-h|--help*
+
+[manarg]
+*mergecap*
+*-v|--version*
+
+== DESCRIPTION
+
+*Mergecap* is a program that combines multiple saved capture files into
+a single output file specified by the *-w* argument. *Mergecap* knows
+how to read *pcap* and *pcapng* capture files, including those of
+*tcpdump*, *Wireshark* and other tools that write captures in those
+formats.
+
+By default, *Mergecap* writes the capture file in *pcapng* format, and
+writes all of the packets from the input capture files to the output file.
+
+*Mergecap* is able to detect, read and write the same capture files that
+are supported by *Wireshark*.
+The input files don't need a specific filename extension; the file
+format and an optional gzip, zstd or lz4 compression will be automatically detected.
+Near the beginning of the DESCRIPTION section of xref:wireshark.html[wireshark](1) or
+https://www.wireshark.org/docs/man-pages/wireshark.html
+is a detailed description of the way *Wireshark* handles this, which is
+the same way *Mergecap* handles this.
+
+*Mergecap* can write the file in several output formats.
+The *-F* flag can be used to specify the format in which to write the
+capture file, *mergecap -F* provides a list of the available output
+formats.
+
+Packets from the input files are merged in chronological order based on
+each frame's timestamp, unless the *-a* flag is specified. *Mergecap*
+assumes that frames within a single capture file are already stored in
+chronological order. When the *-a* flag is specified, packets are
+copied directly from each input file to the output file, independent of
+each frame's timestamp.
+
+The output file frame encapsulation type is set to the type of the input
+files if all input files have the same type. If not all of the input
+files have the same frame encapsulation type, the output file type is
+set to WTAP_ENCAP_PER_PACKET. Note that some capture file formats, most
+notably *pcap*, do not currently support WTAP_ENCAP_PER_PACKET.
+This combination will cause the output file creation to fail.
+
+== OPTIONS
+
+-a::
++
+--
+Causes the frame timestamps to be ignored, writing all packets from the
+first input file followed by all packets from the second input file. By
+default, when *-a* is not specified, the contents of the input files
+are merged in chronological order based on each frame's timestamp.
+
+Note: when merging, *mergecap* assumes that packets within a capture
+file are already in chronological order.
+--
+
+-F <file format>::
++
+--
+Sets the file format of the output capture file. *Mergecap* can write
+the file in several formats; *mergecap -F* provides a list of the
+available output formats. By default this is the *pcapng* format.
+--
+
+-h|--help::
+Print the version number and options and exit.
+
+-I <IDB merge mode>::
++
+--
+Sets the Interface Description Block (IDB) merge mode to use during merging.
+*mergecap -I* provides a list of the available IDB merge modes.
+
+Every input file has one or more IDBs, which describe the interface(s) the
+capture was performed on originally. This includes encapsulation type,
+interface name, etc. When mergecap merges multiple input files, it has to
+merge these IDBs somehow for the new merged output file. This flag controls
+how that is accomplished. The currently available modes are:
+
+*none*: No merging of IDBs is performed, and instead all IDBs are
+copied to the merged output file.
+
+*all*: IDBs are merged only if all input files have the same number
+of IDBs, and each IDB matches their respective entry in the
+other files. (Only the IDBs that occur at the beginning of the files,
+before any packet blocks, are compared. IDBs that occur later in the
+files are merged with duplicates iff the initial IDBs were merged.)
+This is the default mode.
+
+*any*: Any and all duplicate IDBs are merged into one IDB, regardless
+of what file they are in.
+
+Note that an IDB is only considered a matching duplicate if it has the same
+encapsulation type, name, speed, time precision, comments, description, etc.
+--
+
+-s <snaplen>::
++
+--
+Sets the snapshot length to use when writing the data.
+If the *-s* flag is used to specify a snapshot length, frames in the
+input file with more captured data than the specified snapshot length
+will have only the amount of data specified by the snapshot length
+written to the output file. This may be useful if the program that is
+to read the output file cannot handle packets larger than a certain size
+(for example, the versions of snoop in Solaris 2.5.1 and Solaris 2.6
+appear to reject Ethernet frames larger than the standard Ethernet MTU,
+making them incapable of handling gigabit Ethernet captures if jumbo
+frames were used).
+--
+
+-v|--version::
+Print the full version information and exit.
+
+-V::
+Causes *mergecap* to print a number of messages while it's working.
+
+-w <outfile>|-::
+Sets the output filename. If the name is '*-*', stdout will be used.
+This setting is mandatory.
+
+include::diagnostic-options.adoc[]
+
+== EXAMPLES
+
+To merge two capture files together into a third capture file, in which
+the last packet of one file arrives 100 seconds before the first packet
+of another file, use the following sequence of commands.
+
+First, use:
+
+ capinfos -aeS a.pcap b.pcap
+
+to determine the start and end times of the two capture files, as
+seconds since January 1, 1970, 00:00:00 UTC.
+
+If a.pcap starts at 1009932757 and b.pcap ends at 873660281, then the
+time adjustment to b.pcap that would make it end 100 seconds before
+a.pcap begins would be 1009932757 - 873660281 - 100 = 136272376 seconds.
+
+Thus, the next step would be to use:
+
+ editcap -t 136272376 b.pcap b-shifted.pcap
+
+to generate a version of b.pcap with its time stamps shifted 136272376
+ahead.
+
+Then the final step would be to use :
+
+ mergecap -w compare.pcap a.pcap b-shifted.pcap
+
+to merge a.pcap and the shifted b.pcap into compare.pcap.
+
+== SEE ALSO
+
+xref:https://www.tcpdump.org/manpages/pcap.3pcap.html[pcap](3), xref:wireshark.html[wireshark](1), xref:tshark.html[tshark](1), xref:dumpcap.html[dumpcap](1), xref:editcap.html[editcap](1), xref:text2pcap.html[text2pcap](1),
+xref:https://www.tcpdump.org/manpages/pcap-filter.7.html[pcap-filter](7) or xref:https://www.tcpdump.org/manpages/tcpdump.1.html[tcpdump](8)
+
+== NOTES
+
+*Mergecap* is based heavily upon *editcap* by Richard Sharpe
+<sharpe[AT]ns.aus.com> and Guy Harris <guy[AT]alum.mit.edu>.
+
+This is the manual page for *Mergecap* {wireshark-version}.
+*Mergecap* is part of the *Wireshark* distribution.
+The latest version of *Wireshark* can be found at https://www.wireshark.org.
+
+HTML versions of the Wireshark project man pages are available at
+https://www.wireshark.org/docs/man-pages.
+
+== AUTHORS
+
+.Original Author
+[%hardbreaks]
+Scott Renfro <scott[AT]renfro.org>
+
+.Contributors
+[%hardbreaks]
+Bill Guyton <guyton[AT]bguyton.com>