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       faketime - manipulate the system time for a given command


       faketime [options] timestamp program [arguments...]


       The  given  command  will  be  tricked  into believing that the current
       system time is the one specified in the timestamp. The wall clock  will
       continue to run from this date and time unless specified otherwise (see
       advanced  options).  Actually,  faketime  is  a  simple   wrapper   for
       libfaketime,  which  uses  the  LD_PRELOAD  mechanism  to  load a small
       library which intercepts system calls to functions such as time(2)  and
       fstat(2).   This   wrapper  exposes  only  a  subset  of  libfaketime’s
       functionality; please refer to the README file that came with  faketime
       for more details and advanced options.


       --help show usage information and quit.

              show version information and quit.

       -m     use the multi-threading variant of libfaketime.

       -f     use the advanced timestamp specification format.


       faketime ’last Friday 5 pm’ /bin/date
       faketime ’2008-12-24 08:15:42’ /bin/date
       faketime -f ’+2,5y x10,0’ /bin/bash -c ’date; while true; do echo $SECONDS ; sleep 1 ; done’
       faketime -f ’+2,5y x0,50’ /bin/bash -c ’date; while true; do echo $SECONDS ; sleep 1 ; done’
       (Please note that it depends on your locale settings whether . or , has to be used for fractional offsets)


       The  simple  timestamp  format used by default applies the /bin/date -d
       command to parse user-friendly specifications such  as  ’last  friday’.
       When  using  the  faketime  option  -f,  the timestamp specified on the
       command line is directly passed to libfaketime, which enables a  couple
       of additional features such as speeding the clock up or slowing it down
       for the target program. It is strongly recommended that you have a look
       at the README file that came with faketime for the details. Summary:

       Freeze clock at absolute timestamp: "YYYY-MM-DD hh:mm:ss"
              If  you  want to specify an absolute point in time, exactly this
              format must be used. Please note  that  freezing  the  clock  is
              usually  not  what  you want and may break the application. Only
              use if you know what you’re doing!

       Relative time offset: "[+/-]123[m/h/d/y], e.g. "+60m", "+2y"
              This is the most often used format and specifies the faked  time
              relatively  to the current real time. The first character of the
              format string must be a + or a -. The numeric value  by  default
              represents seconds, but the modifiers m, h, d, and y can be used
              to specify minutes, hours, days,  or  years,  respectively.  For
              example,  "-2y"  means  "two years ago". Fractional time offsets
              can be used, e.g. "+2,5y", which means "two and a half years  in
              the  future". Please note that the fraction delimiter depends on
              your locale settings, so if "+2,5y" does  not  work,  you  might
              want to try "+2.5y".

       Start-at timestamps: "@YYYY-MM-DD hh:mm:ss"
              The  wall  clock  will start counting at the given timestamp for
              the program. This can be used for specifying absolute timestamps
              without freezing the clock.


       When  using  relative time offsets or start-at timestamps (see ADVANCED
       TIMESTAMP FORMAT above and option -f), the clock speed can be adjusted,
       i.e.  time  may  run  faster  or  slower  for the executed program. For
       example, "+5y x10" will set the faked time 5 years into the future  and
       make  the time pass 10 times as fast (one real second equals 10 seconds
       measured by the program). Similarly, the flow of time  can  be  slowed,
       e.g. using "-7d x0,2", which will set the faked time 7 days in the past
       and set the clock speed to 20 percent, i.e. it takes  five  real  world
       seconds  for  one  second  measured by the program. Again, depending on
       your locale, either "x2.0" or "x2,0"  may  be  required  regarding  the

       Faking   times  for  multiple  programs  or  even  system-wide  can  be
       simplified by using ~/.faketimerc  files  and  /etc/faketimerc.  Please
       refer to the README that came with faketime for warnings and details.


       Maintained  by  Wolfgang Hommel <>. Please see the
       README and Changelog files for contributers.


       Due to limitations of the LD_PRELOAD mechanism, faketime will not  work
       with  suidroot  and  statically  linked programs.  While timestamps and
       time offsets will work for child processes, speeding the  clock  up  or
       slowing  it  down  might  not  work  for child processes spawned by the
       executed program as expected; a new instance of libfaketime is used for
       each  child process, which means that the libfaketime start time, which
       is used in speed adjustments, will also be re-initialized.


       Please send an e-mail to Wolfgang Hommel <>


       Copyright © 2003-2008 by Wolfgang Hommel.

       There is NO warranty; not even for MERCHANTABILITY  or  FITNESS  FOR  A
       PARTICULAR  PURPOSE.  You may redistribute copies of faketime under the
       terms of the GNU General Public License.
       For more information about these matters, see the file named COPYING.

SEE ALSO, time(2), fstat(2)