BCCS199_Session_11

Question 1

A process is…?

Answer 1

a program in execution.

Question 2

Processes are defined by a process control block, which include…?

Answer 2

• Process ID
• Process priority
• Process state
• Location of program in memory
• Address of next instruction to be executed
• List of resources held by the process
• Etc, etc, etc

Question 3

When creating a process, the parent process ____ and the child process ______.

Answer 3

• The parent process duplicates itself (forking)
• The child process runs a new program (execing)

Typically, the parent process waits for the child to die, as when executing a command in bash, though there are exceptions.

Question 4

Processes can be in one of five states:

Answer 4

• R: Runnable
• S: Voluntary Sleep
• D: Involuntary Sleep
• T: Stopped (Suspended) Processes
• Z: Zombie

Question 5

Every process has a…?

Answer 5

numerical priority associated with it.

The lower the number, the higher the priority.

This priority can be adjusted up or down with the nice command.

Question 6

All running processes get a chance to go during a…?

Answer 6

scheduling “epoch”; higher priority processes get more time.

At the end of the epoch, processes are re-evaluated.

Question 7

Signals can be sent to a process for various reasons:

Answer 7

• Hardware error, e.g. divide by zero
• Software conditions, e.g. child dies or window resized
• Terminal interrupts (CTRL-C and CTRL-Z)
• Processes can send signals to other processes for various reasons, if owned by same user

See slide 7 for signal list.

Question 8

Jobs can be run in…?

Answer 8

foreground (can’t do anything else) or background (can do other things).

From command line, finishing with “&” runs the command in the background

Question 9

Foreground jobs can be interrupted with …?

Answer 9

CTRL-Z. then resumed with fg or run the background with bg.

Question 10

A list of running jobs can be generated with the…?

Answer 10

jobs command.

Question 11

Programs can be scheduled to run with the…?

Answer 11

at command.

Question 12

A list of scheduled commands can be viewed with the…?

Answer 12

atq command.

Question 13

The cron command can be used to…?

Answer 13

schedule tasks to run at a specific time and day of the week or month.

Question 14

cron tasks are defined in the…?

Answer 14

cron table.

Question 15

The cron table is edited with the …?

Answer 15

crontab command.