let command in Linux with Examples

14 Jul, 2021
The let command is used to evaluate arithmetic expressions on shell variables. 
Syntax:  
let [expression]
Options: 
 
Basic arithmetic operators : The addition(+), subtraction(-), multiplication(*), division(/) and modulus(%) operators can be used in the expression with the let command. Example:let "myvar =2" "myvar1=1" "myvar2=myvar1+myvar"; echo $myvar2
let "myvar =2" "myvar1=1" "myvar2=myvar1-myvar"; echo $myvar2
let "myvar =2" "myvar1=1" "myvar2=myvar1*myvar"; echo $myvar2
let "myvar =2" "myvar1=1" "myvar2=myvar1/myvar"; echo $myvar2
let "myvar =2" "myvar1=1" "myvar2=myvar1%myvar"; echo $myvar2
Example:
let "myvar =2" "myvar1=1" "myvar2=myvar1+myvar"; echo $myvar2
let "myvar =2" "myvar1=1" "myvar2=myvar1-myvar"; echo $myvar2
let "myvar =2" "myvar1=1" "myvar2=myvar1*myvar"; echo $myvar2
let "myvar =2" "myvar1=1" "myvar2=myvar1/myvar"; echo $myvar2
let "myvar =2" "myvar1=1" "myvar2=myvar1%myvar"; echo $myvar2
Post-increment(var++) / Post-decrement(var–) operator : This operator is used to interpret the integer value then increase/decrease the integer variable by 1.Example:let "myvar=2" "myvar2=myvar++" ; echo $myvar $myvar2
let "myvar=2" "myvar2=myvar++" ; echo $myvar $myvar2
In the above example, myvar2 gets the value of myvar2 before the increment occurs.
In the above example, myvar2 gets the value of myvar2 before the increment occurs.
Pre-increment(++var) / Pre-decrement(–var) operator : This operator increases/decreases the integer value by 1 and then interpret the integer variable.Example:let "myvar=10" "myvar2=--myvar"; echo $myvar $myvar2
let "myvar=10" "myvar2=--myvar"; echo $myvar $myvar2
In the above example, the change in value occurs first then the value gets stored in myvar2.
In the above example, the change in value occurs first then the value gets stored in myvar2.
Unary plus(+exp) / Unary minus(-exp) : This operator is used to multiply a given expression by 1 or -1. Example:  
Example: 
 
In the above example, The value of myvar changes from positive to negative with unary minus operator.
In the above example, The value of myvar changes from positive to negative with unary minus operator.
Bit-wise negation(~) : This operator is used to negate every bit of the integer value i.e., turns 0 to 1 and 1 to 0.Example:let "myvar=0" "myvar= ~myvar"; echo $myvar
let "myvar=0" "myvar= ~myvar"; echo $myvar
In the above example, The value myvar is ‘0000...00’ in binary while the negation is ‘1111...11’ which is the 2’s complement value of -1.
In the above example, The value myvar is ‘0000...00’ in binary while the negation is ‘1111...11’ which is the 2’s complement value of -1.
Exponent(**) operator : This operator is used to raise one quantity to the power of another.Example:let "myvar= 5 ** 2" ; echo $myvar
let "myvar= 5 ** 2" ; echo $myvar
Bitwise shift left / Bitwise shift right : This operator is used to shift the order of the bits either to the left or right.Example:let "myvar = 5 << 2"; echo $myvar
let "myvar = 5 << 2"; echo $myvar
Bitwise AND operator : This operator does a bitwise comparison between two bits and returns 1 if both are 1 else returns 0.Example:let "myvar=5" "myvar2=4" "myvar3 = myvar & myvar2" ; echo $myvar3
let "myvar=5" "myvar2=4" "myvar3 = myvar & myvar2" ; echo $myvar3
Bitwise OR operator : This operator does a bitwise comparison between two bits and returns 1 if atleast one the bits is 1, else returns 0.Example:let "myvar=7" "myvar2=4" "myvar3= myvar | myvar2" ; echo $myvar3
let "myvar=7" "myvar2=4" "myvar3= myvar | myvar2" ; echo $myvar3
Bitwise XOR operator : This operator does a bitwise comparison between two bits and returns 0 if they are alike, else returns 1.Example:let "myvar=7" "myvar2=4" "myvar3= myvar ^ myvar2" ; echo $myvar3
let "myvar=7" "myvar2=4" "myvar3= myvar ^ myvar2" ; echo $myvar3
Akanksha_Rai
gulshankumarar231
linux-command
Linux-Shell-Commands
Linux-Unix
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