Bash — Numbers

Arithmetic operations

#!/bin/bash

a=10
b=3

echo "Add: $((a + b))"    # 13
echo "Sub: $((a - b))"    # 7
echo "Mul: $((a * b))"    # 30
echo "Div: $((a / b))"    # 3
echo "Mod: $((a % b))"    # 1

Increment and decrement

#!/bin/bash

x=5
x=$((x + 1))  # 6
((x++))        # 7
((x--))        # 6
echo "$x"

Comparison

#!/bin/bash

a=10
b=20

[ $a -eq $b ] && echo "Equal"
[ $a -ne $b ] && echo "Not equal"
[ $a -gt $b ] && echo "Greater"
[ $a -lt $b ] && echo "Less"
[ $a -ge $a ] && echo "Greater or equal"
[ $a -le $a ] && echo "Less or equal"

Floating point (bc)

#!/bin/bash

a=3.14
b=2.0

result=$(echo "$a * $b" | bc)
echo "Result: $result" # 6.28

result=$(echo "scale=2; $a / $b" | bc)
echo "Division: $result" # 1.57

Number formatting

#!/bin/bash

printf "%d\n" 42       # 42
printf "%05d\n" 42     # 00042
printf "%f\n" 3.14159  # 3.141590
printf "%.2f\n" 3.14159 # 3.14
printf "%e\n" 100000   # 1.000000e+05
printf "%x\n" 255      # ff
printf "%o\n" 255      # 377

Random numbers

#!/bin/bash

# Random 0-32767
echo $RANDOM

# Random in range
min=1
max=100
range=$((max - min + 1))
random=$((RANDOM % range + min))
echo "Random: $random"

Mini Practice

Write Bash code that:

1. Performs all arithmetic operations
2. Compares two numbers
3. Uses bc for floating-point math
4. Formats numbers with printf

Up Next

In the next lesson, you'll learn about Arrays — working with arrays in Bash.