declare:tldr:d329c

The declare -i command in Bash is used to declare a variable as an integer. The ${variable} represents the name of the variable you want to declare, and "${value}" represents the value that you want to assign to the variable.

With the -i option, Bash treats the variable as an integer and performs arithmetic operations on it. If the assigned value is not a valid integer, it will be treated as zero. For example, if you set value="abc", the variable will be initialized to 0.

Here's an example to illustrate its usage:

declare -i number=5
echo $number   # Output: 5

number="abc"
echo $number   # Output: 0

number=10/2
echo $number   # Output: 5, as 10 divided by 2 is equal to 5

In the above example, the variable number is declared as an integer using declare -i command. The first assignment sets its value to 5. When we assign a non-numeric value "abc" to it, it is treated as 0. Lastly, we assign 10/2 to the variable, and it performs the arithmetic operation which evaluates to 5.