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clockdiff(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | WARNINGS | SEE ALSO | REFERENCES | AUTHOR | SECURITY | AVAILABILITY | COLOPHON 

CLOCKDIFF(8)                     iputils                     CLOCKDIFF(8)

NAME         top

       clockdiff - measure clock difference between hosts

SYNOPSIS         top


       clockdiff [-o] [-o1] [--time-format ctime iso] [-V] {destination}

DESCRIPTION         top

       clockdiff Measures clock difference between us and destination
       with 1 msec resolution using ICMP TIMESTAMP [2] packets or,
       optionally, IP TIMESTAMP option [3] added to ICMP ECHO. [1]

OPTIONS         top

       -o
           Use IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP
           messages. It is useful with some destinations, which do not
           support ICMP TIMESTAMP (f.e. Solaris <2.4).

       -o1
           Slightly different form of -o, namely it uses three-term IP
           TIMESTAMP with prespecified hop addresses instead of four term
           one. What flavor works better depends on target host.
           Particularly, -o is better for Linux.

       -T, --time-format ctime iso
           Print time stamp in output either ISO-8601 format or classical
           ctime format. The ctime format is default. The ISO time stamp
           includes timezone, and is easier to parse.

       -I
           Alias of --time-format iso option and argument.

       -h, --help
           Print help and exit.

       -V, --version
           Print version and exit.

WARNINGS         top

           • Some nodes (Cisco) use non-standard timestamps, which is
           allowed by RFC, but makes timestamps mostly useless.

           • Some nodes generate messed timestamps (Solaris>2.4), when
           run xntpd. Seems, its IP stack uses a corrupted clock source,
           which is synchronized to time-of-day clock periodically and
           jumps randomly making timestamps mostly useless. Good news is
           that you can use NTP in this case, which is even better.

           • clockdiff shows difference in time modulo 24 days.

SEE ALSO         top

       ping(8), arping(8), tracepath(8).

REFERENCES         top

       [1] ICMP ECHO, RFC0792, page 14.

       [2] ICMP TIMESTAMP, RFC0792, page 16.

       [3] IP TIMESTAMP option, RFC0791, 3.1, page 16.

AUTHOR         top

       clockdiff was compiled by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>.
       It was based on code borrowed from BSD timed daemon.

SECURITY         top

       clockdiff requires CAP_NET_RAW and CAP_SYS_NICE capabilities to be
       executed. It is safe to be used as set-uid root.

AVAILABILITY         top

       clockdiff is part of iputils package.

COLOPHON         top

       This page is part of the iputils (IP utilities) project.
       Information about the project can be found at 
       ⟨http://www.skbuff.net/iputils/⟩.  If you have a bug report for
       this manual page, send it to yoshfuji@skbuff.net,
       netdev@vger.kernel.org.  This page was obtained from the project's
       upstream Git repository ⟨https://github.com/iputils/iputils.git⟩
       on 2025-08-11.  (At that time, the date of the most recent commit
       that was found in the repository was 2025-06-06.)  If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a
       mail to man-pages@man7.org

iputils 20250605                                             CLOCKDIFF(8)

Pages that refer to this page: arping(8)

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