Quotations

Shell has single and double quotations to signify a string. However, they do have great differences between them.

Single Quotation (')

Single quotation instructs shell not to interpret any special characters like backslash and variable and treat it as a pure string.

$ echo ‘hello’’world’

Helloworld

$ echo ‘hello world’

hello world

$ echo ‘$hello’$world

$hello

$ echo ‘hello

> world’

hello

world

$ echo *

<all sort of files>

$ echo ‘*’

*

$ world='universe'

$ echo 'Hello $world'

Hello $world

$

This is suitable for solid string statement where you want to form a string or a command without interpretation.

Exception

If you wish to have special characters like newline (\n) interpreted, add a dollar sign ($) in front. E.g.:

$ echo $'Name\tAge\nBob\t24\nMary\t36'

Name  Age

Bob   24

Mary  36

$

You got a table instead of the long weird sentence.

Double Quotation (")

Double quotation instructs shell to interpret any special character within the line, generating the resultant output as a string.

$ echo “hello””world”

helloworld

$ echo “hello world”

hello world

$ echo “$hello”$world

$ echo “hello

> world”

hello

world

$ echo *

...

$ echo “*”

*

$ 

$ world="universe"

$ echo "Hello $world"

Hello universe

$

Backslash (\n)

Backslash uses for 2 functionalities:

1. Denote special characters like newline (\n), tab (\t), etc.
2. Cancel functional character and retain it as a string, like double-quote itself.

They are interpreted by double quotation automatically. Example:

$ world="universe"

$ echo -e "Hello \n $world"

Hello 

 universe

$ echo "Hello \"Hermione\""

Hello "Hermione"

$

That's all about quotation in SHELL. Use it to your advantage! You may proceed to the next section.