Data types in Bash

There is no typing in Bash

  • Bash variables do not have types thus bash is neither loosely or strictly typed. Anything you apply the identity operator against becomes a character string variable.
  • Bash is however able to distinguish numerical strings which is why arithmetic operations and comparisons work.
  • Consequently there is no null type either. The closest thing is an empty string, i.e. APPROX_NULL="" .

Declarations

You can achieve a sort of typing through the declare keyword, although bear in mind this is not enforced and you do not have to use it.

-r : readonly

declare -r var1="I'm read only"

Roughly equivalent to a const : if you attempt to change the value of var1 it will fail with an error message.

i : integer

declare -i var2="43"

The script will treat all subsequent occurrences of var2 as an integer

a : array

declare -a anArray
logo