Shell Chapter 3 quotation marks and operators

2.2 quotation marks

1, double quotation marks
Double quotation marks can reference any character except '(reverse quotation marks), $, \
2, single quotes
Single quotation marks ignore any referenced values. In other words, if special meanings are shielded, All characters in the quotation marks, including quotation marks, are considered as a string.
3. Reverse quotation marks
Shell executes the content in the back quotes as a command.
4, \ backslash
SHIELD special characters from common characters
& * + ^ '|?

Operator
1, bitwise Operator
~ OP1 anti-Operator
OP1 <OP2 left shift operator
> Right shift operator
& Comparison Operators
^ XOR operator
| Or operator

$ [] Tell the expressions in Shell brackets to evaluate

2. logical operators
&&

3. Value assignment operator
=, + =,-=, * =,/=, & =

Let command to assign values to expressions
Let COUNT = $ count + $ change
Let count + = change
[Root] Var = 65
Let var + = 4
Echo $ VaR
$ []