arithmetic expressions

Q1: What exactly is an arithmetic expression in Bash? An arithmetic expression in Bash allows you to perform calculations and manipulate numeric values. Expressions like 1 + 2 or a * b are evaluated using Bash's arithmetic context, which you can invoke using double parentheses, $(( expression )). Q2: What are side effects in the context of arithmetic expressions? In programming, side effects refer to changes that an operation makes apart from returning a value, which may affect the state elsewhere in the system or script. In Bash arithmetic, side effects are most commonly seen with the increment ++ and decrement -- operators. They modify the value of a variable and, at the same time, use the new or old value in an expression.

Q: Why does (( i++ )) return 1 when i is initialized to 0, and what is its effect when using set -e in a Bash script? A: When i is set to 0, the expression (( i++ )) first returns the value of i, and then increments i by 1. In the context of arithmetic expressions in Bash, a return value of 0 is considered "false", and any non-zero value is considered "true". Therefore, when i is 0, (( i++ )) evaluates the value of i (which is 0, thus "false"), and then increments i. Since the evaluation was "false", the return status of the command is 1, contrary to what might be intuitively expected.