Bash - check if number is less than

In this article, we would like to show you how to check if number is less than another number in Bash.

Practical example

In this example, we use -lt operator to check if number is less than another number inside if statement.

script.sh file:

#!/bin/bash

number=3

if [ "$number" -lt 5 ]; then
    echo "$number is less than 5"
fi

Note: this approach should be used in POSIX shells where other solutions may not work.

Run in command line:

./script.sh

Output:

3 is less than 5

Altermative notation

1. test based solution

#!/bin/bash

number=3

if test "$number" -lt 5; then
    echo "$number is less than 5"
fi

Note: [ ] notation is shorthand of test command.

2. [[ ]] based solution

#!/bin/bash

number=3

if [[ "$number" -lt 5 ]]; then
    echo "$number is less than 5"
fi

Note: [[ ]] notation is like extended test command, adding additional features (e.g. regular expressions).

3. (( )) based solution

#!/bin/bash

number=3

if (( "$number" < 5 )); then
    echo "$number is less than 5"
fi

Note: (( )) notation was created to simplyfy conditions (like in C language).

See also

1. Bash - compare number variable to another number