Content Type: Variable Attributes

Attributes

The Bash language does not have a type system. It stores all scalar variables in memory as strings. At the same time, Bash has arrays. They are composite types, because an array is a combination of strings.

When we declare a variable in Bash, we should choose if it is scalar or composite. We make this choice by specifying the metadata for the variable. Such metadata is called attributes. The attributes also define the constancy and scope of a variable.

The declare Bash built-in specifies the variable attributes. When we call it without parameters, declare prints all local and environment variables. The set command prints the same output. The declare command has the -p option. The option adds variable attributes to the output data.

If we need information on a particular variable, we pass its name to the declare command. Below is an example of the PATH variable:

declare -p PATH

Try the commands discussed in this lesson in the terminal below.