105.1 Lesson 2

Question 1

Where does a shell/local variable live?

Answer 1

In the shell in which they were created.

Question 2

Where does an environment/global variable live?

Answer 2

In the shell where they were created and in children shells and/or processes.

Question 3

Where do you configure variables, aliases and functions for a shell?

Answer 3

In startup files.

Question 4

Accessing the value of a variable is called

Answer 4

variable referencing

Question 5

How do you reference the variable distro?

Answer 5

$distro

Question 6

Which characters may the name of a variable contain?

Answer 6

a-Z
A-Z
0-9
underscore _

Question 7

What is wrong with the variable 1distro?

Answer 7

It starts with a number.

Question 8

What is wrong with the variable “my distro”=zorinos?

Answer 8

It contains a space

Question 9

The value of a variable is also called

Answer 9

reference

Question 10

Which characters may the value of a variable contain?

Answer 10

a-z
A-Z
0-9
most other characters
$ ! * . / etc.

Question 11

What is wrong with the following variable value?

distro=zorin 12.4

Answer 11

It contains a space and is not enclosed in quotes.

Question 12

When must a variable value be enclosed in quotes?

Answer 12

When it contains
<
>
or
| (pipe symbol)

Question 13

Are single and double quotes always interchangeable?

Answer 13

no

Question 14

What do the semantics of single and double quotes depend on?

Answer 14

If they are used for assigning or for referencing

Question 15

How do single quotes interpret characters of a variable’s value in the context of variable assignment?

Answer 15

literally

Question 16

How is $lizard interpreted during variable assignment when using double quotes?

Answer 16

The variable $lizard is substituted with its value.

Question 17

What happens to initial and extra spaces in a variables value during variable referencing when no double quotes are used?

Answer 17

The spaces get lost.

Question 18

How do you avoid field splitting and pathname expansion when referencing a variable?

Answer 18

echo “$lizard”

Question 19

Variables in bash are also called

Answer 19

shell parameters

Question 20

variable referencing is also called

Answer 20

shell parameter expansion

Question 21

How many expansions does shell parameter expansion consist of?

Answer 21

7

Question 22

Name one expansion that is carried out during shell parameter expansion?

Answer 22

word splitting

Question 23

What happens in the word splitting process of shell parameter expansion?

Answer 23

The result of the other expansions is split into words using the shell parameter $IFS.

Question 24

What is the default value of $IFS?

Question 25

What happens to space tab and newline characters that do not delimit words during word splitting?

Answer 25

They are ommited.

Question 26

What happens during filename expansion?

Answer 26

Bash scans each word for the characters * ? and [ . If a word is found the word is replaced with a list of filenames matching the pattern.

Question 27

What does an exclamation mark that is not the last character in the string refer to in a variables value?

Answer 27

a history event

Question 28

backslashes in variable values must be

Answer 28

escaped with another backslash

Question 29

if a backslash is the last character in a variables value it is interpreted as a

Answer 29

newline

Question 30

create an immutable variable

Answer 30

``` readonly reptile=tortoise #or reptile=tortoise readonly reptile ```

Question 31

List all readonly variables in our current session

Answer 31

``` readonly #or readonly -p ```

Question 32

output all the currently assigned shell variables and functions

Answer 32

set

Question 33

spawn a child process in the current shell

Answer 33

bash

Question 34

unset the variable reptile

Answer 34

unset reptile