Shell implementation Arithmetic Simple method

When you just learned to write shell batches, there is no need to base your logic operations on the basics: arithmetic, here's a simple implementation method in the Linux shell.
1. Simple method
$ b=$ ((5*5+5-3/2))
$ echo $b
29
In the Linux shell, we can use $ (()) to put the expression in parentheses to achieve the function of the operation.
2. Other methods:
Using: Expr to implement operations
$ expr 5-4
1
Note: Write an expression that requires an operation after expr, guaranteeing that there are spaces between the arguments and the operation symbol.

Category	Grammar	Description
Conditional judgment	Expr1 \| Expr2	Returns EXPR1 if EXPR1 is not 0 or null, otherwise returns EXPR2.
Expr1 \& EXPR2	If both EXPR1 and expr2 are nonzero or null, return to EXPR1, or return 0.
Arithmetic	Expr1 + EXPR2	Returns the value after Expr1 plus expr2.
Expr1-expr2	Returns the value after Expr1 minus expr2.
expr1\* EXPR2	Returns the value of Expr1 multiplied by EXPR2.
Expr1/expr2	Returns the value of Expr1 except EXPR2.
Expr1% EXPR2	Returns the remainder of the EXPR1 except EXPR2.
Size judgment	Expr1 \> EXPR2	Returns 1 if EXPR1 is greater than EXPR2, otherwise returns 0. If Expr1 and expr2 are numbers, they are judged by the size of numbers, otherwise they are judged by words. The following are the same.
Expr1 \< EXPR2	If EXPR1 is less than EXPR2, return 1, or return 0.
EXPR1 = Expr2	Returns 1 if Expr1 equals EXPR2, otherwise returns 0.
Expr1! = Expr2	If EXPR1 is not equal to EXPR2, it returns 1, otherwise returns 0.
Expr1 \>= EXPR2	Returns 1 if EXPR1 is greater than or equal to EXPR2, otherwise returns 0.
Expr1 \<= EXPR2	Returns 1 if EXPR1 is less than or equal to EXPR2, otherwise returns 0.
word processing	Expr1:expr2	Compares a fixed string, that is, regular expression. You can use the following characters to assist: . Matches one character. $ to find the end of the string. [List] to find any string that matches the list. * Search for 0 or more words before *. \ (\) returns the string that matches the parentheses.

3. Floating-point arithmetic

$ expr 5.0-4
Expr:non-integer argument

$ echo $ ((5.0-4))

-BASH:5.0-4: syntax error in expression (Error token is ". 0-4")

From the above results, it appears that the above expression is not sufficient to support floating-point arithmetic. The data found: Bash does not support floating-point arithmetic, if you need to do floating-point arithmetic, need to use Bc,awk processing.

Method One:
[Email protected] ~]$ c=$ (echo "5.01-4*2.0" |BC)
[Email protected] ~]$ echo $c
-2.99
Method Two:
[[email protected] ~]$ c=$ (awk ' begin{print 7.01*5-4.01} ')
[Email protected] ~]$ echo $c
31.04

Note: $ () in the shell is equivalent to '. The middle contains the command statement execution, which returns the execution result.

Shell implementation Arithmetic Simple method