Linux in a Nutshell, 6th Edition

Quoting

Quoting disables a character’s special meaning and allows it to be used literally, as itself. The following table displays characters that have special meaning to the Bash shell.

Character	Meaning
;	Command separator
&	Background execution
( )	Command grouping
|	Pipe
< > &	Redirection symbols
* ? [ ] ~ + - @ !	Filename metacharacters
" ' \	Used in quoting other characters
`	Command substitution
$	Variable substitution (or command or arithmetic substitution)
space tab newline	Word separators

These characters can be used for quoting:

" "

Everything between " and " is taken literally, except for the following characters that keep their special meaning:

$

Variable (or command and arithmetic) substitution will occur.

'

Command substitution will occur.

"

This marks the end of the double quote.

' '

Everything between ' and ' is taken literally except for another '. You cannot embed another ' within such a quoted string.

\

The character following a \ is taken literally. Use within " " to escape “, $, and '. Often used to escape itself, spaces, or newlines.

$” "

Just like " ", except that locale translation is done.

$' '

Similar to ' ', but the quoted text is processed for the following escape sequences.

Sequence	Value	Sequence	Value
\a	Alert	\t	Tab
\b	Backspace	\v	Vertical tab
\c X	Control character X	\ nnn	Octal value nnn
\e	Escape	\xnn	Hexadecimal value nn
\E	Escape	\'	Single quote
\f	Form feed	\”	Double quote
\n	Newline	\\	Backslash
\r	Carriage return

Examples

$ echo 'Single quotes "protect" double quotes' Single quotes "protect" double quotes $  ...