1FAKETIME(1) wolfcw FAKETIME(1)
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6 faketime - manipulate the system time for a given command
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9 faketime [options] timestamp program [arguments...]
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12 The given command will be tricked into believing that the current sys‐
13 tem time is the one specified in the timestamp. The wall clock will
14 continue to run from this date and time unless specified otherwise (see
15 advanced options). Actually, faketime is a simple wrapper for libfake‐
16 time, which uses the LD_PRELOAD mechanism to load a small library which
17 intercepts system calls to functions such as time(2) and fstat(2). This
18 wrapper exposes only a subset of libfaketime's functionality; please
19 refer to the README file that came with faketime for more details and
20 advanced options, or have a look at http://github.com/wolfcw/libfake‐
21 time
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24 --help show usage information and quit.
25 --version
27 show version information and quit.
28 -m use the multi-threading variant of libfaketime.
30 -f use the advanced timestamp specification format.
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35 faketime 'last Friday 5 pm' /bin/date
36 faketime '2008-12-24 08:15:42' /bin/date
37 faketime -f '+2,5y x10,0' /bin/bash -c 'date; while true; do echo $SECONDS ; sleep 1 ; done'
38 faketime -f '+2,5y x0,50' /bin/bash -c 'date; while true; do echo $SECONDS ; sleep 1 ; done'
39 faketime -f '+2,5y i2,0' /bin/bash -c 'while true; do date ; sleep 1 ; done'
40 In this single case all spawned processes will use the same global clock without restaring it at the start of each process.
41 (Please note that it depends on your locale settings whether . or , has to be used for fractional offsets)
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45 The simple timestamp format used by default applies the /bin/date -d
46 command to parse user-friendly specifications such as 'last friday'.
47 When using the faketime option -f, the timestamp specified on the com‐
48 mand line is directly passed to libfaketime, which enables a couple of
49 additional features such as speeding the clock up or slowing it down
50 for the target program. It is strongly recommended that you have a look
51 at the libfaketime documentation. Summary:
52 Freeze clock at absolute timestamp: "YYYY-MM-DD hh:mm:ss"
54 If you want to specify an absolute point in time, exactly this
55 format must be used. Please note that freezing the clock is usu‐
56 ally not what you want and may break the application. Only use
57 if you know what you're doing!
58 Relative time offset: "[+/-]123[m/h/d/y], e.g. "+60m", "+2y"
60 This is the most often used format and specifies the faked time
61 relatively to the current real time. The first character of the
62 format string must be a + or a -. The numeric value by default
63 represents seconds, but the modifiers m, h, d, and y can be used
64 to specify minutes, hours, days, or years, respectively. For
65 example, "-2y" means "two years ago". Fractional time offsets
66 can be used, e.g. "+2,5y", which means "two and a half years in
67 the future". Please note that the fraction delimiter depends on
68 your locale settings, so if "+2,5y" does not work, you might
69 want to try "+2.5y".
70 Start-at timestamps: "@YYYY-MM-DD hh:mm:ss"
72 The wall clock will start counting at the given timestamp for
73 the program. This can be used for specifying absolute timestamps
74 without freezing the clock.
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77 When using relative time offsets or start-at timestamps (see ADVANCED
78 TIMESTAMP FORMAT above and option -f), the clock speed can be adjusted,
79 i.e. time may run faster or slower for the executed program. For exam‐
80 ple, "+5y x10" will set the faked time 5 years into the future and make
81 the time pass 10 times as fast (one real second equals 10 seconds mea‐
82 sured by the program). Similarly, the flow of time can be slowed, e.g.
83 using "-7d x0,2", which will set the faked time 7 days in the past and
84 set the clock speed to 20 percent, i.e. it takes five real world sec‐
85 onds for one second measured by the program. Again, depending on your
86 locale, either "x2.0" or "x2,0" may be required regarding the delim‐
87 iter. You can also make faketime to advance the reported time by a pre‐
88 set interval upon each time() call independently from the system's time
89 using "-7d i2,0", where "i" is followed by the increase interval in
90 seconds.
91 Faking times for multiple programs or even system-wide can be simpli‐
93 fied by using ~/.faketimerc files and /etc/faketimerc. Please refer to
94 the README that came with faketime for warnings and details.
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97 Please see the README and NEWS files for contributers.
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100 Due to limitations of the LD_PRELOAD mechanism, faketime will not work
101 with suidroot and statically linked programs. While timestamps and
102 time offsets will work for child processes, speeding the clock up or
103 slowing it down might not work for child processes spawned by the exe‐
104 cuted program as expected; a new instance of libfaketime is used for
105 each child process, which means that the libfaketime start time, which
106 is used in speed adjustments, will also be re-initialized. Some pro‐
107 grams may dynamically load system libraries, such as librt, at run-time
108 and therefore bypass libfaketime. You may report programs that do not
109 work with libfaketime, but only if they are available as open source.
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112 Please use https://github.com/wolfcw/libfaketime/issues
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115 Copyright © 2003-2013 by the libfaketime authors.
116 There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
118 PARTICULAR PURPOSE. You may redistribute copies of faketime under the
119 terms of the GNU General Public License.
120 For more information about these matters, see the file named COPYING.
121
123 ld.so(1), time(2), fstat(2)
124faketime 0.9.6 June 2014 FAKETIME(1)