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 falseAND 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.
1 2 3 4 5 6 7 8 9 10 11 | #!/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.
1 2 3 4 5 6 7 8 9 10 11 | #!/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.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | #!/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.
4 Comments
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.
Hi Mark, I have updated the tutorial with a modern approach.
Thank you for your valuable suggestions.
Thank you so much! I was so lost, could not find this anywhere. 🙂
Thank You. 🙂