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
sleepctl
SLEEPCTL(1) General Commands Manual SLEEPCTL(1)
NAME
sleepctl - enable/disable sleepd
SYNOPSIS
sleeptcl [on|off|status]
DESCRIPTION
sleepctl allows temporarily disabling of the sleepd(8) daemon, by a regular user. This can be useful when you're in the middle of a long
download or compile, and don't want the system going to sleep in the middle.
"sleepctl off" makes sleepd not put the system to sleep even if it thinks it is idle. If this command is run more than once, the requests
stack up, and a like number of "sleepctl on" commands must be run to re-enable sleeping. This may be useful if multiple automated processes
or users use the command. Note that the system may still be put to sleep for other reasons, such as a failing battery.
"sleepctl on" re-enables sleeping. If sleeping is re-enabled and sleepd has seen no system activity for some time, and has been prevented
from putting the system to sleep, it may put the system to sleep immediatly.
"sleepctl status" outputs the current status of sleepd.
Note that if the system is forced to sleep by other means, sleepd will not remember what mode it was in when it wakes back up, and will
return to the default mode of putting the system to sleep after some amount of inactivity. This is by design, so you may easily and natu-
rally undo the effects of a "sleepctl off" without remembering to turn it back on.
This program communicates with sleepd by writing to the file /var/run/sleepd.ctl. As such, it needs read/write access to that file. It also
needs to run as whatever user sleepd runs as, so it can hup the daemon.
EXAMPLES
sleepctl off ; wget http://foo/huge.tgz ; sleepctl on
SEE ALSO
sleepd(8)
http://kitenet.net/~joey/code/sleepd/
AUTHOR
Joey Hess <joey@kitenet.net>
SLEEPCTL(1)