Week Two

Question 1

What is UNIX?

Answer 1

Unix is an operating System.

• Controls Hardware
• Everything is a file
• Unix is also a specification

Question 2

Explain the Unix Philosophy

Answer 2

• Make each program do ONE thing well
• Expect output of one program to be the input of another program
• Design + build software to be tried EARLY
• Use tools to lighten a programming task
• No output is GOOD. Output means an error.

Question 3

Standard Components found in an operating system?

Answer 3

Kernel, System Call interface, User Interface.

Question 4

Default standard Input/Output

Answer 4

stdin (keyboard, standard input) stdout (screen, standard output) sterr (screen, standard error)

Question 5

Does unix have segmented directories?

Answer 5

Unix has no segmented directories, for example, in a Windows environment, you might have C, D drive. Linux is a tree-based system.

Question 6

What is a ‘here’ document?

Answer 6

A ‘here’ document is used to redirect output. This ‘<

Question 7

What is a ‘hard’ link?

Answer 7

Every document has at least one hard link and that is to itself. Hard links refer to the physical location of a file.

Question 8

What is a ‘soft’ link?

Answer 8

A soft link is similar to a shortcut in windows. It is a ‘symbolic link’.

Question 9

What kind of systems can Linux run on?

Answer 9

Linux can run on a wide variety of hardware, including arm systems, raspberry pi & Desktop computers.

Question 10

Acronyms GUI / CLI?

Answer 10

Graphical User Interface | Command Line Interface

Question 11

Is Linux a Unix?

Answer 11

Technically, no. Opengroup oversees licensing for Unix. Posix is the standard to which it must adhere to be ‘unix’ compliant. So while Linux is Posix compliant, it is not to be ‘unix’ licensed.

Question 12

What is POSIXs?

Answer 12

POSIX is the standard used to specify if something is unix compliant.

Question 13

What is the Unix kernel?

Answer 13

The unix kernel is loaded into memory during the booting process and is always residing in physical memory. It is a process that must always be running. It is responsible for:

• CPU scheduling
• Memory for processes
• Managing file systems
• Interacting with devices

Question 14

What is dev/null

Answer 14

It is a void - black hole

Question 15

When should cat be used?

Answer 15

If cat is not necessary, do not use it. It takes up extra resoucres.

Question 16

What is a pipe?

Answer 16

Pipes are used to chain commands together.

ls -1a | wc -1

Question 17

What does a dot before a file indicate in the linux system?

Answer 17

A dot indicates a hidden file, these are often configuration files.

Question 18

What is a shell?

Answer 18

A shell is a command interpreter. It is a layer between system function calls and the user. It is an application that gives the user the capacity to give commands to the operating system.

Question 19

What is bash?

Answer 19

Bash is a unix shell. A command-line interface for interacting with the operating system. Bash is -not- your terminal, but it does run inside your terminal.

Question 20

ls -a

Answer 20

The -a option will show you additional hidden files (dot files).

Question 21

Piping - ‘>’

Answer 21

This will redirect the output of a command to a file on disk. This will OVERWRITE if the file already exists so be careful.

Question 22

Piping - ‘»’

Answer 22

This will append to an existing file on disk.

Question 23

Piping - ‘

Answer 23

This will read the input from a disk file rather than the user.

Question 24

Piping - ‘|’

Answer 24

This will pass the output of one command to the next for further processing.

Question 25

What are the permission triads?

Answer 25

The first group represents the owner, the second group represents the group and the third represents everyone else. In each group, you can set permissions for read, write and execute. In octol, 0000 represents no permissions at all.