Conditional Statements in Bash: Using Multiple Conditions with If Statements

Conditional statements are a fundamental part of any programming language, and Bash is no exception. In this tutorial, we will explore how to use multiple conditions with if statements in Bash.

If statements are used to execute a block of code based on certain conditions. The basic syntax of an if statement is:

if condition; then
    # code to be executed
fi

However, often we need to check for multiple conditions and perform different actions based on those conditions. This can be achieved using logical operators such as && (and), || (or), and ! (not).

Let’s consider an example where we want to check two variables, my_error_flag and my_error_flag_o, and perform certain actions based on their values.

my_error_flag=1
my_error_flag_o=2

if [ $my_error_flag -eq 1 ] || [ $my_error_flag_o -eq 2 ]; then
    echo "Error occurred"
else
    echo "No error"
fi

In this example, we use the -eq operator to check if my_error_flag is equal to 1 or my_error_flag_o is equal to 2. If either condition is true, the code inside the if block will be executed.

We can also combine multiple conditions using logical operators.

if [ $my_error_flag -eq 1 ] && [ $my_error_flag_o -eq 2 ]; then
    echo "Both errors occurred"
elif [ $my_error_flag -eq 1 ] || [ $my_error_flag_o -eq 2 ]; then
    echo "One error occurred"
else
    echo "No error"
fi

In this example, we use the && operator to check if both conditions are true. If not, we use the || operator to check if either condition is true.

Another way to write conditional statements in Bash is using the [[ ]] or (( )) keywords.

if [[ $my_error_flag -eq 1 || $my_error_flag_o -eq 2 ]]; then
    echo "Error occurred"
fi

if (( $my_error_flag == 1 || $my_error_flag_o == 2 )); then
    echo "Error occurred"
fi

The [[ ]] keyword is used for string comparisons, while the (( )) keyword is used for arithmetic comparisons.

It’s worth noting that when using multiple conditions with if statements, it’s essential to use parentheses to group the conditions correctly.

if ([ $my_error_flag -eq 1 ] && [ $my_error_flag_o -eq 2 ]) || [ $my_error_flag -eq 3 ]; then
    echo "Error occurred"
fi

In conclusion, conditional statements in Bash are a powerful tool for making decisions based on certain conditions. By using logical operators and grouping conditions correctly, you can write efficient and effective if statements to handle multiple conditions.