POSIX Shell

Quoting

echo 'abc def'
			abc\\ def
			"abc def" # can add more stuffs in

Some special characters that needs to be avoided

• " double quote and ' single quote can be used to express string
• \ escape character, | pipeline
• • any number of characters
• [ → for regex
• & → running in background

• → comment, $variable

• = → assignment
• SPC, NEWLINE, and TAB → separate arguments
• ~ → home directory
• ! → command line substitution
  • !! → execute the previous command (bash-specific)

Non-special characters

letters, digits,

+ - @ % ^ _ / , { } ]

Tokens

• | pipe , & runs in background