## Unix-Operators

## Arithmetic Operators:-

Assume variable **a** holds **10 **and variable **b** holds** 20** then:

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. |

## Relational Operators:-

Assume variable a holds 10 and variable b holds 20 then:

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. |

## Boolean Operators:-

Assume variable a holds 10 and variable b holds 20 then:

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. |

## String Operators:-

Assume variable a holds “abc” and variable b holds “efg” then:

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. |

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