How to Compare Numbers in Bash: Syntax and Examples

In bash, you compare numbers using the if statement combined with test expressions like -eq (equal), -ne (not equal), -lt (less than), -le (less or equal), -gt (greater than), and -ge (greater or equal). Use these inside square brackets [ ] or double square brackets [[ ]] for numeric comparisons.

Syntax

Use if with test expressions inside square brackets to compare numbers. The common operators are:

• -eq: equal
• -ne: not equal
• -lt: less than
• -le: less than or equal
• -gt: greater than
• -ge: greater than or equal

Example syntax:

if [ number1 -operator number2 ]; then
  # commands
fi

bash

if [ number1 -eq number2 ]; then
  echo "Numbers are equal"
fi

Example

This example compares two numbers and prints which one is greater or if they are equal.

bash

#!/bin/bash
num1=10
num2=20

if [ $num1 -eq $num2 ]; then
  echo "$num1 is equal to $num2"
elif [ $num1 -lt $num2 ]; then
  echo "$num1 is less than $num2"
else
  echo "$num1 is greater than $num2"
fi

Output

10 is less than 20

Common Pitfalls

Common mistakes include:

• Using == inside single square brackets for numbers (it works for strings, not numbers).
• Not adding spaces around brackets and operators.
• Forgetting to use $ before variable names.

Correct numeric comparison requires -eq, -lt, etc., inside [ ] with spaces.

bash

# Wrong way:
num1=5
num2=10
if [ $num1 == $num2 ]; then
  echo "Equal"
fi

# Right way:
if [ $num1 -eq $num2 ]; then
  echo "Equal"
fi

Quick Reference

Operator	Meaning
-eq	Equal to
-ne	Not equal to
-lt	Less than
-le	Less than or equal to
-gt	Greater than
-ge	Greater than or equal to

Key Takeaways

Use -eq, -ne, -lt, -le, -gt, and -ge inside [ ] for numeric comparisons in bash.

Always put spaces around brackets and operators in test expressions.

Use $ before variable names to get their values in comparisons.

Avoid using == for numbers; it is for string comparison in single brackets.

Double square brackets [[ ]] support more features but -eq style operators remain standard for numbers.