quotation marks
'Single quotes Full citations i.e. all contents included in the string variable name which is not to be construed
"Double quotes incomplete references will be resolved if the contents of the variable contains variable names
For example a = "hello" if b = '$ a' case b is the content of A $; if b = "$ a" hello content for case b
`Backquote Run with $ () Replace e.g. a =` ls` corresponding to a = $ (ls)
brackets
() An array definition embodiment = A (1. 3 2) 2 (()) arithmetic A $ = ((1 + 2)). 3 $ () Run
[] . 1 test command returns a logical operation on file number string 2 [[]] extended test can be used directly to compare logical operators
<> 1 input and output redirection 2 compare the size
{} A variable reference 2 range {1..9} have 1-99 digit
calculating signs
Arithmetic + - * / **% subtraction, multiplication and division to take over power
Comparative <> = greater than or less
Logic && ||! AND-OR
Other symbols
# Comments followed content will not be executed computer
; Two sequentially executed statements | pipe symbol is also connected to two statements 2 case in conjunction ;;
. And source commands to perform the same script in the current shell environment
~ Home directory
, Division symbol
* Wildcard matching any number of any character ? Matches an arbitrary character
$ Variable references
| Pipeline
& Background symbol
'' Space
Escape symbol \
Letter escapes \ n newline \ t similar tab keyboard
Symbols escape if the above symbols can not be displayed inside the string in front of the symbol plus \ to display