How to Declare and Utilize Booleans in Bash

1. Bash Booleans
2. Using 0 or 1 as Booleans in Bash

In Bash, there are no Booleans. However, we may specify the shell variable with values of 0 or False and 1 or True based on our requirements. Bash, on the other hand, supports logical boolean operators. It is required when the script must create output based on a variable’s True or False value.

Bash Booleans

Let’s look at an example.

#!/bin/bash
sunny=true
if $sunny ; then
  echo 'Its a hot day!'
fi

Output:

Its a hot day!

Save the above script and run in terminal. Now, let’s change sunny to false.

#!/bin/bash
sunny=false
if $sunny ; then
  echo 'Its a hot day!'
  else
  echo 'May be rainny!'
fi

Output:

May be rainny!

Using 0 or 1 as Booleans in Bash

Let’s look at an example. We have set sunny to 0 and used -eq to compare numerical values.

#!/bin/bash
sunny=0
if [ $sunny -eq 0 ]; then
  echo 'Its a hot day!'
fi

Output:

Its a hot day!