What is the use of Linux's let command

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Let simple calculator that executes arithmetic expressions.

Summary let arg [arg...] The main purpose is to execute one or more arithmetic expressions.

Parameter arg: arithmetic expression

The return value returns 1 if the last expression executed by let evaluates to 0, otherwise 0. When the divisor of the expression executed by let is 0, 1 is returned and an error is reported.

Operator precedence decrement table operator describes id++, id-- variable increment, variable decrement + + id,-- id variable pre-increment, variable pre-decrement -, + positive sign, negative sign!, ~ logical No, inverse * * exponentiation *, /,% multiplication, division, remainder +,-addition, subtraction > move left by bit, move right =, compare = = ! = equal to or not equal to & bitwise and ^ bitwise XOR\ | bitwise or & & logic and\ | Logic or expr? Expr: expr conditional operator (ternary operator) =, * =, / =,% =, + =,-=, > =, & =, ^ =,\ | = assignment example # attempts to execute arithmetic expressions directly in the terminal (like IDLE in python). 3-4 bash:3+4:command not found... # another way. 3 + 4 bash:3:command not found... # it doesn't seem to work. # let command assignment. Let axioms 4 echo ${a} # shows 81. # (()) Is equivalent to the let command. ) # let is often used for variable assignment, while the external command expr can directly return the value of an expression. Let 3 # 4 # does not display 7. # displays 7 after execution, pay attention to the space. Expr 3 + 4 # conditional expression. If ((8 > 4)); then echo'8 is greater than 4.' Else echo 'error' fi # pay attention to the spaces. If [[12-le 10]]; then echo 'error' else echo' 12 is greater than 10.' Fi # can perform arithmetic operations by setting integer properties with the declare command. The # local command is similar. # No integer attribute specified, output as the string 'aroomb'. Declare axiom 3 bounded 4 c c=a+b echo ${c} # but you can assign values in the following ways. ((aqb)) echo ${c} # shows that 7 # can be added directly if the integer property is set. Declare-I axiom 3 bang 4 c c=a+b echo ${c} # Ibid. Declare-I a number 2, 3, echo ${a} # shows 6. Note that this command is a bash built-in command. For help, please see the help command.

In addition to let, there are external commands such as expr, bc, and so on.

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