apmsleep − go into suspend or standby mode and wake-up later
apmsleep [−sSnwhVd] [−−suspend] [−−standby] [−−noapm] [−−wait] [−−precise] [−−help] [−−version]
Some computers, especially laptops, can wake-up from a low-power suspend to DRAM mode using the
Real-time-clock (RTC) chip. Apmsleep can be used to set the alarm time in the RTC and to go into sus-
pend or standby mode. An interrupt from the RTC causes the computer to wake-up. The program detects
this event, by waiting for a leap in the kernel time and terminates successfully. If no time leap occurs within
one minute, or something goes wrong, the exit value will be non-zero.
The wake-up time can be specified in two formats:
+hh:mm specifies a relative offset to the current time. The computer will suspend for exactly hh hours and
mm minutes plus a few seconds to wake up. On some laptops, the timing is not completely accurate so it
may be a few minutes (or more?) late.
hh:mm specifies absolute local time in 24-hour format. The time stored in the RTC is not important. You
may change the time zone used, with the TZ environment variable as usual. Daylight saving time is not
obeyed in this version, but might be in a future release. WARNING: Do not close cover of laptop after
suspending the laptop with apmsleep. Most laptops overheat when running with closed cover.
Energy conservation with APM is little for a desktop. Turning of the screen will save 1/2, going into
standby with drives turned off will save another 1/6th of the current.
Print the apmsleep program version and exit immediately.
Put the machine into suspend mode if possible (default). On my laptop, suspend mode turns off
ev erything except the memory.
Put the machine into standby mode if possible. On my laptop, standby mode turns off screen, hard
disk, and CPU.
Wait indefinitely for the time leap.
Wait for alarm time to match actual time. Do not wait for time leap. This