Cdelahou: Replaced content with "MOVED"

2012-10-25T03:57:46Z

Replaced content with "MOVED"

← Older revision		Revision as of 03:57, 25 October 2012
Line 1:		Line 1:
	~~Here are some (unofficial) answers to the midterm practice questions~~		MOVED

	~~1) False. Sparse file means holes. Zeroes aren't holes.~~
	~~YOu need to move the file pointer. You have to use a~~
	~~seek. The data will be READ as zeros, though...~~
	~~Look up truncate command and strace it. It ain't just writing zeros~~

	2)
	~~Nothing happens. Env vars aren't globals. They're passed in with Execve. Environments~~
	~~variables are typically process specific.~~

	3)
	~~rwx~~

	4)
	~~Kill the parent~~
	~~Why? init will own the zombie process and then kill it~~

	5)
	~~chmod +x~~
	~~Default non executable. Need to make it executable. (--x)~~

	6)
	~~Software interrupt~~

	7)
	~~Don't know... Undefined. Can not depend on ordering~~

	8)
	~~True. That's the purpose of signals~~
	~~Register a normal C function as a signal handler~~
	~~Some are implemented by default (sigkill)~~
	~~Signals can be called at any point in execution.~~

	9)
	~~Sequentially (sysV). Shell script that runs every ''command'' sequentially~~

	~~Upstart does in in parrallel though...~~

	~~10)~~
	~~execve DOES NOT RETURN ANYTHING. Process image is replaced.~~

	~~The program itself calls the signal handler~~

	~~11)~~
	~~fsck <- wrapper function~~
	~~fsck.FMT <- called by fsck for a specific format (ex: fsck.ext4)~~

	~~12)~~
	~~The kernel. The kernel is the only thing that can allocate.(execve)~~
	~~This also makes sense because execve is a system call.~~

	~~13)~~
	~~Sparse file.~~

	~~14)~~
	~~lspci, lshw.~~
	~~In /proc/, you may be able to also.~~
	~~These commands display the machine's "hardware".~~

	~~Not /dev/ because that's the abstraction.~~


	~~15)~~
	~~At the command line, the $PATH variable is where the shell looks for binaries/files.~~
	~~The path is walked when the fullPATH/filename of the command line hasn't been specified~~

	~~16)~~
	~~Some libraries make no sys calls (strlen). Libraries that do basic string and math~~
	~~operations -> no sys calls~~

	~~Programs with lots of I/O will use lot of sys calls~~

	~~17)~~
	~~nice and renice~~
	~~nicess is policy value (default value and you can modify this)~~
	~~priority (dynamic) is based on niceness and the amount of time the process has run on~~
	~~cpu~~
	~~Priority doesn't apply to I/O. I/O will continue despite other processing having high~~
	~~priority. I/O will always slow down the system.~~

	~~18)~~
	~~The former requires a library card and a telephone.~~

Cdelahou: my notes about the answers

2012-10-25T03:56:05Z

my notes about the answers

New page

Here are some (unofficial) answers to the midterm practice questions

1) False. Sparse file means holes. Zeroes aren't holes.
YOu need to move the file pointer. You have to use a
seek. The data will be READ as zeros, though...
Look up truncate command and strace it. It ain't just writing zeros

2)
Nothing happens. Env vars aren't globals. They're passed in with Execve. Environments
variables are typically process specific.

3)
rwx

4)
Kill the parent
Why? init will own the zombie process and then kill it

5)
chmod +x
Default non executable. Need to make it executable. (--x)

6)
Software interrupt

7)
Don't know... Undefined. Can not depend on ordering

8)
True. That's the purpose of signals
Register a normal C function as a signal handler
Some are implemented by default (sigkill)
Signals can be called at any point in execution.

9)
Sequentially (sysV). Shell script that runs every ''command'' sequentially

Upstart does in in parrallel though...

10)
execve DOES NOT RETURN ANYTHING. Process image is replaced.

The program itself calls the signal handler

11)
fsck <- wrapper function
fsck.FMT <- called by fsck for a specific format (ex: fsck.ext4)

12)
The kernel. The kernel is the only thing that can allocate.(execve)
This also makes sense because execve is a system call.

13)
Sparse file.

14)
lspci, lshw.
In /proc/, you may be able to also.
These commands display the machine's "hardware".

Not /dev/ because that's the abstraction.

15)
At the command line, the $PATH variable is where the shell looks for binaries/files.
The path is walked when the fullPATH/filename of the command line hasn't been specified

16)
Some libraries make no sys calls (strlen). Libraries that do basic string and math
operations -> no sys calls

Programs with lots of I/O will use lot of sys calls

17)
nice and renice
nicess is policy value (default value and you can modify this)
priority (dynamic) is based on niceness and the amount of time the process has run on
cpu
Priority doesn't apply to I/O. I/O will continue despite other processing having high
priority. I/O will always slow down the system.

18)
The former requires a library card and a telephone.

COMP 3000 2012 Midterm Material Answers - Revision history

Cdelahou: Replaced content with "MOVED"

Cdelahou: my notes about the answers