Bash Reference Manual
Quoting is used to remove the special meaning of certain
characters or words to the shell. Quoting can be used to
disable special treatment for special characters, to prevent
reserved words from being recognized as such, and to prevent
Each of the shell metacharacters (see section 2. Definitions)
has special meaning to the shell and must be quoted if it is to
When the command history expansion facilities are being used, the
history expansion character, usually `!', must be quoted
to prevent history expansion. See section 9.1 Bash History Facilities, for
more details concerning history expansion.
There are three quoting mechanisms: the
escape character, single quotes, and double quotes.