math.txt

# Bash Arithmetic Primer: (( ))

# 1. Basic arithmetic (no output, just evaluation)
# \e[38;5;201mNB:\e[0m no \e[1m$\e[0m before variable names when used inside (( ))
((x = 5 + 3))       \e[36m# spaces are optional\e[0m
echo $x \e[36m# 8\e[0m

# 2. Conditions
if ((x < 10)); then
  echo "x is small"
fi

# 3. Increment/decrement
((x++))             \e[36m# post-increment\e[0m
((--x))             \e[36m# pre-decrement\e[0m

# 4. Boolean logic (0 = false, non-zero = true)
((0))               \e[36m# false (exit code 1)\e[0m
((1))               \e[36m# true  (exit code 0)\e[0m

# 5. Return value check
((5 > 3))           \e[36m# exit code is 0 (true)\e[0m
echo $?             \e[36m# prints 0\e[0m
((5 < 3))           \e[36m# exit code is 1 (false)\e[0m
echo $?             \e[36m# prints 1\e[0m

# 6. To output a result: use \e[1m$\e[0m(( ))
echo $((5 + 5))     \e[36m# prints 10
# you can also use this way to set variables in the more common format:
x=$((3*3)) \e[36m# $x is 9\e[0m