05-09-2005
Please make sure that you have read our
rules. And note:
(6) Do not post classroom or homework problems.
But we sometimes bend this rule when a student has done a lot of work. So I'll make a few comments based on a quick scan of your code. This line of code:
while(1) sleep(1);//run
is dangerous. Why do you have it? I would delete it. If you meant to do something like:
while (1) { List() ; sleep(1) ; }
then you have the fork() in the wrong place. You need to fork() once at the beginning of the program. At present, your program is running List() once and then falling into your infinite sleep loop. You have some re-writing to do.
wait(30);
is illegal and also dangerous. I don't even know what you want to happen there. The last thing you do in List is to ignore some signals. You should ignore signals earlier. If you put List() in a loop, you need to move the signal calls to near the beginning somewhere.
Your instructor probably told you to check if the parent pid is 1, but your instructor is wrong. That is not the definition of a daemon. As it happens, you can probably get away with test you have. But the definition of a daemon is a program with no controlling terminal. You could check that by attempting to open /dev/tty. A daemon must fail but a non-damon must succeed.
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LEARN ABOUT DEBIAN
sleepd
SLEEPD(8) System Manager's Manual SLEEPD(8)
NAME
sleepd - puts a laptop to sleep during inactivity or on low battery
SYNOPSIS
sleepd [-s command] [-d command] [-u n] [-U n] [-I] [-i n] [-E] [-e filename] [-a] [-l n] [-w] [-n] [-v] [-c n] [-b n] [-A] [-H] [-N
[device] [-r n] [-t n]]
DESCRIPTION
sleepd is a daemon to force laptops to go to sleep after some period of inactivity. This is useful if your laptop does not automatically go
to sleep when you aren't using it, and, like me, you often forget to shut it off. It is also capable of suspending a laptop when its bat-
tery gets very low.
sleepd can detect activity in several ways. The default is to poll both event devices and interrupts to detect when your laptop is in use
due to keyboard or mouse activity. It defaults to polling /dev/input/event*. You may specify a list of device files to poll instead, or
use options to enable other means of checking for activity (network activity, utmp, or load average). After a configurable amount of time
with no activity, sleepd runs a program to put the laptop to sleep.
OPTIONS
-h, --help
Show summary of options.
-n, --nodaemon
Don't fork to background; run in forground.
-v, --verbose
Output status messages.
-u, --unused
Number of seconds the laptop can remain idle before being put to sleep. Defaults to 600 seconds (10 minutes). Set to 0 to disable
any sleeping due to idleness.
-U, --ac-unused
If set, controls the number of seconds the laptop can remain idle before being put to sleep when running on AC power. If not set,
the laptop will not sleep when it's on AC power.
-e, --event
Adds an event file to the list that is watched. Using this switch disables polling all files in /dev/input/event*.
-E, --no-events
This switch disables event device polling.
-l, --load
If set, a load average higher than this number will prevent the computer from sleeping If not set, the computer will ignore the load
average.
-w If set, sleepd will also check idletime based on utmp. This will prevent the system from sleeping while remote connections are
active. It uses the time limit from -u.
-i, --irq
Adds an irq to the list that is watched. Using this switch disables automatic detection of keyboard and mouse irqs unless -a is
specified as well.
-I, --no-irq
This switch disables interrupt polling.
-a, --auto
Automatically detect and watch mouse and keyboard irqs.
-s, --sleep-command
Command to run to put the laptop to sleep. Defaults to "apm -s" for systems with APM and "pm-suspend" for systems with ACPI.
-b, --battery
If this option is specified, the daemon will put the laptop to sleep if the percentage of battery charge drops below the specified
number and the system is off AC power. This is useful for some laptops which don't handle this themselves. It supports using APM,
ACPI, and HAL for querying battery status.
-d, --hibernate-command
A command to run instead of the regular sleep command when the battery is low. This can be useful if you want to make the system go
to sleep when it's not active, but suspend to disk if the battery is low. If not set, the sleep command is used.
-N, --netdev
Monitor a network interface for activity based on packet count. eth0 is the default. This option may be used more than once with
different network interfaces.
-t, --tx-min
Set a baseline transmit raffic rate in packets per second for network monitoring. Requires -N.
-r, --rx-min
Set a baseline receive traffic rate in packets per second for network monitoring. Requires -N.
-A, --and
Only go to sleep if all specified conditions are met. For example, only sleep if idle and if the battery is low.
-c, --check-period
Number of seconds between check on system status. Defaults to 10 seconds, which should be fine generally.
-H, --force-hal
Force HAL to be used instead of ACPI or other methods to query battery status.
SEE ALSO
sleepctl(1)
http://kitenet.net/~joey/code/sleepd/
BUGS
Interrupt monitoring cannot always detect keyboard and mouse. If the keyboard or mouse interrupt is shared (as is common with usb
devices), other devices on the same interrupt can keep the system awake. Use event device polling instead.
AUTHOR
Joey Hess <joey@kitenet.net>
SLEEPD(8)