How to declare and use a boolean variable in Linux bash shell script?

The boolean data type is not directly supported in Linux bash shell. But you can use normal variables as boolean in the below ways –

b=true
if $b
then 
  echo "its true"
else
  echo "its false"
fi

b="false"
if [ "$b" == "false" ]
then 
  echo "its false"
else
  echo "its true"
fi

b=true

if $b

then

echo "its true"

else

echo "its false"

b="false"

if [ "$b" == "false" ]

then

echo "its false"

else

echo "its true"