poweroff in C

kantu · 07-02-2009, 05:19 AM

Hi,
I was trying to implement poweroff and reboot in C
How can it be done ?

Sergei Steshenko · 07-02-2009, 05:41 AM

Quote:

Originally Posted by kantu

Hi,
I was trying to implement poweroff and reboot in C
How can it be done ?

Take the source of 'poweroff' command and find the answer there.

unSpawn · 07-02-2009, 05:53 AM

...else please show us what you've got already (if "trying" means you actually tried to code anything) and what the errors are, if any.

wje_lq · 07-02-2009, 10:12 PM

Quote:

Originally Posted by Sergei Steshenko

Take the source of 'poweroff' command and find the answer there.
Quote:

Originally Posted by unSpawn

...else please show us what you've got already (if "trying" means you actually tried to code anything) and what the errors are, if any.

With great enthusiasm, I vote for A.

At least on Slackware, this command (issued while logged in as root so that the PATH environment variable would have a convenient variable)

Code:

file $(which poweroff)

produced:

Code:

/sbin/poweroff: symbolic link to `halt'

Ok, then. It's the same program that does both, and it probably examines argv[0] to determine whether to power off or simply halt. So:

Code:

file $(which halt)

produced:

Code:

/sbin/halt: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), stripped

Now I was getting somewhere.

I explored the source, and discovered that if you have the appropriate man pages installed and you do this at the command line:

Code:

man 2 reboot

then all will be revealed.

Hope this helps.