How to Use Logical OR & AND in Shell Script with Examples

    RahulBy 2 Mins ReadUpdated:

    A logical condition is created, when two or more conditioned produce a single result based on them. Here one condition result may also invert the result of another condition.

    Logical OR & AND operations are very useful where multiple conditions are used in our programs (scripts).

    • OR is used between two or multiple conditions. It returns true if any one of conditions returns as true. First condition is always checked but the second condition is checked only if first condition is returned false
    • AND is used between two or multiple conditions. It returns true only if all the conditions returns as true. First condition is always checked but the second condition is checked only if first condition is returned true

    Using Logical OR (||) in Shell Scripts

    Logical OR in bash script is used with operator -o. Write a small shell script that will show how to use logical OR ( || ) operator between two conditions.

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    #!/bin/bash
     
    read -p "Enter First Numeric Value: " first
    read -p "Enter Second Numeric Value: " second
     
    if [ $first -le 10 ] || [ $second -gt 20 ]
    then
        echo "Atleast one conditions is true"
    else
        echo "Both conditions are failed"
    fi

    Using Logical AND (&&) in Shell Scripts

    Logical AND in bash script is used with operator -a. Below shell script will show you to how to use logical AND ( && ) between two conditions.

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    #!/bin/bash
     
    read -p "Enter First Numeric Value: "  first
    read -p "Enter Second Numeric Value: "  second
     
    if [ $first -le 10 ]  && [ $second -gt 20 ]
    then
        echo "Both conditions are true"
    else
        echo "Atleast one conditions is false"
    fi

    Using Multiple Logical OR & AND

    Now, use the multiple logical operators in a single statement. The below example will help you to understand how to use multiple logical operators in a single statement.

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    #!/bin/bash
     
    # A sample shell script to take input a number from the user
    # Check if the number is between 10 - 20
    # Or number is between 100 - 200
     
    read -p "Enter a number: " num
     
    if ([ $num -ge 10 ] && [ $num -le 20 ]) || ([ $num -ge 100 ] && [ $num -le 200 ])
    then
         echo "Input number ($num) is between 10-20 or 100-200"
    else
         echo "Input number ($num) is neither between 10-20 nor 100-200"
    fi

    Conclusion

    In this tutorial, you have learned about using of logical AND (&&) and logical OR (||) operators in a shell script.

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    5 Comments

    1. Two D Man on

      Even though there is a “modern approach” some of us might be trying to read old scripts. There are plenty of scripts out there that use -o and -a. Do you think, suddenly, they will all stop working?

      Reply
    2. Mark on

      Using “-o” and “-a” is deprecated. The modern approach is “||” and “&&” with enclosing brackets [].

      Also, your example for using multiple and/or in bash does not work and gets a syntax error (you can’t use parenthesis like that inside brackets; did you test it?). You CAN uses parenthesis if using “||” or “&&” outside of brackets.

      Reply

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