Home / server / Questions / 138325
Accepted
nicoulaj
Asked: 2010-05-05 02:56:09 +0800 CST

Faking the date for a specific shell session

  • 772

I'm certainly trying to achieve something weird here, but I want to fake the date locally for a shell session on GNU/Linux. I need to black-box test how a program behaves at different dates, and modifying the system-wide date can have unwanted side effects (cron jobs, messed up logs, etc).

Any ideas ?

linux time unix shell unix-shell

4 Answers

  1. Best Answer

    You can just use executable faketime (from ubuntu repositories sudo apt-get install faketime) by:

    faketime -f "-15d" date

    Or even fake time in whole shell by 

    faketime -f "-15d" bash -l
    • 40

  2. Haven't tried this one out yet. But if this is current is looks like someone already wrote the library you can preload with libfaketime.

    The basic usage is:

    user@host> LD_PRELOAD=/usr/local/lib/libfaketime.so.1 FAKETIME="-15d" date
Mon Nov  8 12:01:12 CEST 2007

    You can use ltrace to make sure all the time functions your application uses are covered.

    • 30

  3. You can set the TZ variable to an oddball value.

    $ date
Tue May  4 06:24:43 CDT 2010
$ date -u
Tue May  4 11:24:47 UTC 2010
$ export TZ='CDT-3:12'
$ date
Tue May  4 14:36:53 CDT 2010
$ export TZ='CDT+5:37'
$ date
Tue May  4 05:48:00 CDT 2010
    • 7

  4. You might be able to preload a library that has an alternative time() implementation.

    • 3