Variables and datatypes in Bash

Types

Variables

We use the equality symbol to create a variable:

stringVar="My first variable"
floatVar="50.3"
boolVar="true"

As there is no typing in bash, the names of these variables are purely notional.

To invoke a variable we use special brackets:

echo ${stringVar} # My first variable
echo ${floatVar} # 50.3
echo ${boolVar} # true
  • Quotation marks at declaration are also not strictly necessary however they can help avoid bugs. Also serves as a reminder that every type is basically a string at the end of the day

Common operations

Check if a variable exists

if [ -v variable_name ]; then
    echo "The variable exists."
else
    echo "The variable does not exist."
fi

Check if a variable is set (defined)

if [ -z "${variable_name+x}" ]; then
    echo "The variable does not exist."
else
    echo "The variable exists."
fi

Parameter expansion

Still not very clear on this.

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