1 Toán tử số học (Arithmetic Operators)
Giả sử có hai biến có giá trị như sau:

 a=10  
 b=20  

Operator	Description	Example
+	Addition - Adds values on either side of the operator	`expr $a + $b` will give 30
-	Subtraction - Subtracts right hand operand from left hand operand	`expr $a - $b` will give -10
*	Multiplication - Multiplies values on either side of the operator	`expr $a \* $b` will give 200
/	Division - Divides left hand operand by right hand operand	`expr $b / $a` will give 2
%	Modulus - Divides left hand operand by right hand operand and returns remainder	`expr $b % $a` will give 0
=	Assignment - Assign right operand in left operand	a=$b would assign value of b into a
==	Equality - Compares two numbers, if both are same then returns true.	[ $a == $b ] would return false.
!=	Not Equality - Compares two numbers, if both are different then returns true.	[ $a != $b ] would return true.

 #!/bin/sh  
 a=10  
 b=20  
 val=`expr $a + $b`  
 echo "a + b : $val"  
   
 val=`expr $a - $b`  
 echo "a - b : $val"  
   
 val=`expr $a \* $b`  
 echo "a * b : $val"  
   
 val=`expr $b / $a`  
 echo "b / a : $val"  
   
 val=`expr $b % $a`  
 echo "b % a : $val"  
   
 if [ $a == $b ]  
 then  
   echo "a is equal to b"  
 fi  
   
 if [ $a != $b ]  
 then  
   echo "a is not equal to b"  
 fi  

 $ ./test.sh  
 a + b : 30  
 a - b : -10  
 a * b : 200  
 b / a : 2  
 b % a : 0  
 a is not equal to b  
   

2 Toán tử quan hệ (Relational Operators)
Giả sử có hai biến có các giá trị như sau:

 a=10  
 b=20  

Operator	Description	Example
-eq	Checks if the value of two operands are equal or not, if yes then condition becomes true.	[ $a -eq $b ] is not true.
-ne	Checks if the value of two operands are equal or not, if values are not equal then condition becomes true.	[ $a -ne $b ] is true.
-gt	Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.	[ $a -gt $b ] is not true.
-lt	Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.	[ $a -lt $b ] is true.
-ge	Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.	[ $a -ge $b ] is not true.
-le	Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.	[ $a -le $b ] is true.

Ex:

 #!/bin/sh  
 a=10  
 b=20  
   
 if [ $a -eq $b ]  
 then  
   echo "$a -eq $b : a is equal to b"  
 else  
   echo "$a -eq $b: a is not equal to b"  
 fi  
   
 if [ $a -ne $b ]  
 then  
   echo "$a -ne $b: a is not equal to b"  
 else  
   echo "$a -ne $b : a is equal to b"  
 fi  
   
 if [ $a -gt $b ]  
 then  
   echo "$a -gt $b: a is greater than b"  
 else  
   echo "$a -gt $b: a is not greater than b"  
 fi  
   
 if [ $a -lt $b ]  
 then  
   echo "$a -lt $b: a is less than b"  
 else  
   echo "$a -lt $b: a is not less than b"  
 fi  
   
 if [ $a -ge $b ]  
 then  
   echo "$a -ge $b: a is greater or equal to b"  
 else  
   echo "$a -ge $b: a is not greater or equal to b"  
 fi  
   
 if [ $a -le $b ]  
 then  
   echo "$a -le $b: a is less or equal to b"  
 else  
   echo "$a -le $b: a is not less or equal to b"  
 fi  
   

 $ ./test.sh   
 10 -eq 20: a is not equal to b  
 10 -ne 20: a is not equal to b  
 10 -gt 20: a is not greater than b  
 10 -lt 20: a is less than b  
 10 -ge 20: a is not greater or equal to b  
 10 -le 20: a is less or equal to b  
   

3 Toán tử  logic (Boolean Operators)
Giả sử có hai biến có các giá trị như sau:

 a=10  
 b=20  

Operator	Description	Example
!	This is logical negation. This inverts a true condition into false and vice versa.	[ ! false ] is true.
-o	This is logical OR. If one of the operands is true then condition would be true.	[ $a -lt 20 -o $b -gt 100 ] is true.
-a	This is logical AND. If both the operands are true then condition would be true otherwise it would be false.	[ $a -lt 20 -a $b -gt 100 ] is false.

Ex:

 #!/bin/sh  
   
 a=10  
 b=20  
   
 if [ $a != $b ]  
 then  
   echo "$a != $b : a is not equal to b"  
 else  
   echo "$a != $b: a is equal to b"  
 fi  
   
 if [ $a -lt 100 -a $b -gt 15 ]  
 then  
   echo "$a -lt 100 -a $b -gt 15 : returns true"  
 else  
   echo "$a -lt 100 -a $b -gt 15 : returns false"  
 fi  
   
 if [ $a -lt 100 -o $b -gt 100 ]  
 then  
   echo "$a -lt 100 -o $b -gt 100 : returns true"  
 else  
   echo "$a -lt 100 -o $b -gt 100 : returns false"  
 fi  
   
 if [ $a -lt 5 -o $b -gt 100 ]  
 then  
   echo "$a -lt 100 -o $b -gt 100 : returns true"  
 else  
   echo "$a -lt 100 -o $b -gt 100 : returns false"  
 fi  

 $./test.sh  
 10 != 20 : a is not equal to b  
 10 -lt 100 -a 20 -gt 15 : returns true  
 10 -lt 100 -o 20 -gt 100 : returns true  
 10 -lt 5 -o 20 -gt 100 : returns false  

4 Toán tử chuỗi (String Operators)
Toán tử chuỗi dùng để so sánh hai chuỗi ký tự.

Giả sử có hai biến chứa các chuối như sau:

 a="abc"  
 b="efg"  

Operator	Description	Example
=	Checks if the value of two operands are equal or not, if yes then condition becomes true.	[ $a = $b ] is not true.
!=	Checks if the value of two operands are equal or not, if values are not equal then condition becomes true.	[ $a != $b ] is true.
-z	Checks if the given string operand size is zero. If it is zero length then it returns true.	[ -z $a ] is not true.
-n	Checks if the given string operand size is non-zero. If it is non-zero length then it returns true.	[ -z $a ] is not false.
str	Check if str is not the empty string. If it is empty then it returns false.	[ $a ] is not false.

Ex:

 #!/bin/sh  
 a="abc"  
 b="efg"  
   
 if [ $a = $b ]  
 then  
   echo "$a = $b : a is equal to b"  
 else  
   echo "$a = $b: a is not equal to b"  
 fi  
   
 if [ $a != $b ]  
 then  
   echo "$a != $b : a is not equal to b"  
 else  
   echo "$a != $b: a is equal to b"  
 fi  
   
 if [ -z $a ]  
 then  
   echo "-z $a : string length is zero"  
 else  
   echo "-z $a : string length is not zero"  
 fi  
   
 if [ -n $a ]  
 then  
   echo "-n $a : string length is not zero"  
 else  
   echo "-n $a : string length is zero"  
 fi  
   
 if [ $a ]  
 then  
   echo "$a : string is not empty"  
 else  
   echo "$a : string is empty"  
 fi  
   

 $ ./test.sh   
 abc = efg: a is not equal to b  
 abc != efg : a is not equal to b  
 -z abc : string length is not zero  
 -n abc : string length is not zero  
 abc : string is not empty  
   

5 Toán tử tệp (File Operators)
Toán tử tệp dùng để kiểm tra các thuộc tính của tệp.

Operator	Description	Example
-b file	Checks if file is a block special file if yes then condition becomes true.
-c file	Checks if file is a character special file if yes then condition becomes true.
-d file	Check if file is a directory if yes then condition becomes true.
-f file	Check if file is an ordinary file as opposed to a directory or special file if yes then condition becomes true.
-g file	Checks if file has its set group ID (SGID) bit set if yes then condition becomes true.
-k file	Checks if file has its sticky bit set if yes then condition becomes true.
-p file	Checks if file is a named pipe if yes then condition becomes true.
-t file	Checks if file descriptor is open and associated with a terminal if yes then condition becomes true.
-u file	Checks if file has its set user id (SUID) bit set if yes then condition becomes true.
-r file	Checks if file is readable if yes then condition becomes true.
-w file	Check if file is writable if yes then condition becomes true.
-x file	Check if file is execute if yes then condition becomes true.
-s file	Check if file has size greater than 0 if yes then condition becomes true.
-e file	Check if file exists. Is true even if file is a directory but exists.

Ex:

 #!/bin/sh  
   
 file="/usr/bin/sh"  
   
 if [ -r $file ]  
 then  
   echo "File has read access"  
 else  
   echo "File does not have read access"  
 fi  
   
 if [ -w $file ]  
 then  
   echo "File has write permission"  
 else  
   echo "File does not have write permission"  
 fi  
   
 if [ -x $file ]  
 then  
   echo "File has execute permission"  
 else  
   echo "File does not have execute permission"  
 fi  
   
 if [ -f $file ]  
 then  
   echo "File is an ordinary file"  
 else  
   echo "This is sepcial file"  
 fi  
   
 if [ -d $file ]  
 then  
   echo "File is a directory"  
 else  
   echo "This is not a directory"  
 fi  
   
 if [ -s $file ]  
 then  
   echo "File size is zero"  
 else  
   echo "File size is not zero"  
 fi  
   
 if [ -e $file ]  
 then  
   echo "File exists"  
 else  
   echo "File does not exist"  
 fi  
   

 $ ./test.sh   
 File has read access  
 File does not have write permission  
 File has execute permission  
 File is an ordinary file  
 This is not a directory  
 File size is zero  
 File exists