How to Bash Ranges

1. Use the for Loop to Get Range in Bash
2. Use the for Loop With Three-Expression to Get Range in Bash
3. Use the while Loop to Get Range in Bash
4. Use eval to Get Range in Bash
5. Use seq to Get Range in Bash

This tutorial demonstrates iterating through a range of integers in bash with for loop and while loop.

Use the for Loop to Get Range in Bash

The bash script below uses a for loop with brace expansion to loop through a range of numbers. The numbers inside the braces are incremented sequentially.

#!/bin/bash

printf "Print Numbers from 0 to 5\n"
for x in {0..5}
do
printf "number:$x\n"
done

Output:

Print Numbers from 0 to 5
number:0
number:1
number:2
number:3
number:4
number:5

Use the for Loop With Three-Expression to Get Range in Bash

The script uses a for loop with a three-expression like in C language. Here, expr1 is the initialization, expr2 is the condition, and expr3 is the increment.

In our case, x is initialized to 0, x is tested if it is less than or equal to 5, and lastly, x is incremented by 1.

#!/bin/bash

max=5
printf "Print Numbers from 0 to $max\n"
for ((x=0;x<=max;x++)); do
    printf "number: $x\n"
done

Output:

Print Numbers from 0 to 5
number: 0
number: 1
number: 2
number: 3
number: 4
number: 5

Use the while Loop to Get Range in Bash

This uses a while loop with a binary comparison operator, -le, that is used for arithmetic value comparison.

In our case, the while loop executes as long as x is less than or equal to the variable $max.

#!/bin/bash

x=0
max=5
printf "Print numbers from $x to $max\n"
while [ $x -le $max ]; do
    printf "number: $x\n"
    x=$(($x+1))
done

Output:

Print numbers from 0 to 5
number: 0
number: 1
number: 2
number: 3
number: 4
number: 5

Use eval to Get Range in Bash

eval is a bash command used to execute arguments as shell commands. In the script below, the braces generate numbers from 0 to $max in increments of 1, the for loop iterates over these numbers, and the printf command displays them.

#!/bin/bash

max=4

printf "Print Numbers from 0 to $max\n"
for x in `eval echo {0..$max}`
do
printf "number: $x\n"
done

Output:

Print Numbers from 0 to 4
number: 0
number: 1
number: 2
number: 3
number: 4

Use seq to Get Range in Bash

seq is a bash command used to generate numbers from start to finish in increment steps.

In our case, seq generates numbers from x to $max in increments of 1. The for loop iterates over these numbers, and the printf command is used to display them.

x=0
max=5

printf "Print numbers from $x to $max\n"
for x in $(seq $x $max)
do
printf "number: $x\n"
done

Output:

Print numbers from 0 to 5
number: 0
number: 1
number: 2
number: 3
number: 4
number: 5