There are 5 basic operators in bash/shell scripting:
- Arithmetic Operators
- Relational Operators
- Boolean Operators
- Bitwise Operators
- File Test Operators
1. Arithmetic Operators: These operators are used to perform normal arithmetics/mathematical operations. There are 7 arithmetic operators:
- Addition (+): Binary operation used to add two operands.
- Subtraction (-): Binary operation used to subtract two operands.
- Multiplication (*): Binary operation used to multiply two operands.
- Division (/): Binary operation used to divide two operands.
- Modulus (%): Binary operation used to find remainder of two operands.
- Increment Operator (++): Unary operator used to increase the value of operand by one.
- Decrement Operator (- -): Unary operator used to decrease the value of a operand by one
#!/bin/bash # reading data from the user read -r -p "Enter a: " a
read -r -p "Enter b: " b
add=$((a+b)) echo "Addition of a and b are: " ${add}
sub=$((a-b)) echo "Subtraction of a and b are: " ${sub}
mul=$((a*b)) echo "Multiplication of a and b are: " ${mul}
div =$((a/b))
echo "Division of a and b are: " ${ div }
mod=$((a%b)) echo "Modulis of a and b are: " ${mod}
((++a)) echo "Increment operator when applied on $a results into a :" "${a}"
((--b)) echo "Decrement operator when applied on 'b' results into b :" "${b}"
|
Output:
2. Relational Operators: Relational operators are those operators which define the relation between two operands. They give either true or false depending upon the relation. They are of 6 types:
- ‘==’ Operator: Double equal to operator compares the two operands. Its returns true is they are equal otherwise returns false.
- ‘!=’ Operator: Not Equal to operator return true if the two operands are not equal otherwise it returns false.
- ‘<‘ Operator: Less than operator returns true if first operand is less than second operand otherwise returns false.
- ‘<=’ Operator: Less than or equal to operator returns true if first operand is less than or equal to second operand otherwise returns false
- ‘>’ Operator: Greater than operator return true if the first operand is greater than the second operand otherwise return false.
- ‘>=’ Operator: Greater than or equal to operator returns true if first operand is greater than or equal to second operand otherwise returns false
#!/bin/bash #reading data from the user read -p 'Enter a : ' a
read -p 'Enter b : ' b
if (( $a==$b ))
then echo a is equal to b.
else echo a is not equal to b.
fi if (( $a!=$b ))
then echo a is not equal to b.
else echo a is equal to b.
fi if (( $a<$b ))
then echo a is less than b.
else echo a is not less than b.
fi if (( $a<=$b ))
then echo a is less than or equal to b.
else echo a is not less than or equal to b.
fi if (( $a>$b ))
then echo a is greater than b.
else echo a is not greater than b.
fi if (( $a>=$b ))
then echo a is greater than or equal to b.
else echo a is not greater than or equal to b.
fi |
Output:
3. Logical Operators : They are also known as boolean operators. These are used to perform logical operations. They are of 3 types:
- Logical AND (&&): This is a binary operator, which returns true if both the operands are true otherwise returns false.
- Logical OR (||): This is a binary operator, which returns true is either of the operand is true or both the operands are true and return false if none of then is false.
- Not Equal to (!): This is a unary operator which returns true if the operand is false and returns false if the operand is true.
#!/bin/bash #reading data from the user read -p 'Enter a : ' a
read -p 'Enter b : ' b
if (($a == "true" & $b == "true" ))
then echo Both are true .
else echo Both are not true .
fi if (($a == "true" || $b == "true" ))
then echo Atleast one of them is true .
else echo None of them is true .
fi if (( ! $a == "true" ))
then echo "a" was initially false .
else echo "a" was initially true .
fi
|
Output:
4. Bitwise Operators: A bitwise operator is an operator used to perform bitwise operations on bit patterns. They are of 6 types:
- Bitwise And (&): Bitwise & operator performs binary AND operation bit by bit on the operands.
- Bitwise OR (|): Bitwise | operator performs binary OR operation bit by bit on the operands.
- Bitwise XOR (^): Bitwise ^ operator performs binary XOR operation bit by bit on the operands.
- Bitwise complement (~): Bitwise ~ operator performs binary NOT operation bit by bit on the operand.
- Left Shift (<<): This operator shifts the bits of the left operand to left by number of times specified by right operand.
- Right Shift (>>): This operator shifts the bits of the left operand to right by number of times specified by right operand.
#!/bin/bash #reading data from the user read -p 'Enter a : ' a
read -p 'Enter b : ' b
bitwiseAND=$(( a&b )) echo Bitwise AND of a and b is $bitwiseAND bitwiseOR=$(( a|b )) echo Bitwise OR of a and b is $bitwiseOR bitwiseXOR=$(( a^b )) echo Bitwise XOR of a and b is $bitwiseXOR bitiwiseComplement=$(( ~a )) echo Bitwise Compliment of a is $bitiwiseComplement leftshift=$(( a<<1 )) echo Left Shift of a is $leftshift rightshift=$(( b>>1 )) echo Right Shift of b is $rightshift |
Output:
5. File Test Operator: These operators are used to test a particular property of a file.
- -b operator: This operator check whether a file is a block special file or not. It returns true if the file is a block special file otherwise false.
- -c operator: This operator checks whether a file is a character special file or not. It returns true if it is a character special file otherwise false.
- -d operator: This operator checks if the given directory exists or not. If it exists then operators returns true otherwise false.
- -e operator: This operator checks whether the given file exists or not. If it exits this operator returns true otherwise false.
- -r operator: This operator checks whether the given file has read access or not. If it has read access then it returns true otherwise false.
- -w operator: This operator check whether the given file has write access or not. If it has write then it returns true otherwise false.
- -x operator: This operator check whether the given file has execute access or not. If it has execute access then it returns true otherwise false.
- -s operator: This operator checks the size of the given file. If the size of given file is greater than 0 then it returns true otherwise it is false.
#!/bin/bash #reading data from the user read -p 'Enter file name : ' FileName
if [ -e $FileName ]
then echo File Exist
else echo File doesnot exist
fi if [ -s $FileName ]
then echo The given file is not empty.
else echo The given file is empty.
fi if [ -r $FileName ]
then echo The given file has read access.
else echo The given file does not has read access.
fi if [ -w $FileName ]
then echo The given file has write access.
else echo The given file does not has write access.
fi if [ -x $FileName ]
then echo The given file has execute access.
else echo The given file does not has execute access.
fi |
Output: