Understanding the seq Command in Linux

The seq command in Linux is a versatile tool that generates a sequence of numbers. It is especially useful in shell scripting and automating repetitive tasks. In this guide, we’ll explore its basic usage, practical applications, and examples.

Basic Usage of the seq Command

1. Generating Numbers with Default Step

The simplest form of the command generates a sequence of numbers starting from 1 with a step of 1.

[root@server ~]# seq 5
1
2
3
4
5

2. Custom Start and End Points

By specifying two numbers, you can define the start and end points.

[root@server ~]# seq 21 25
21
22
23
24
25

3. Adding a Step

Add a third argument to specify the step size. For example, the command below generates numbers from 5 to 50 in increments of 5.

[root@server ~]# seq 5 5 50
5
10
15
20
25
30
35
40
45
50

4. Generating Numbers in Descending Order

Use a negative step size to generate numbers in descending order.

[root@server ~]# seq 10 -1 1
10
9
8
7
6
5
4
3
2
1

Practical Applications of the seq Command

1. Creating Multiple Files

Use the seq command with the touch command to create multiple files at once. The -f option formats the file names.

[root@server seq]# touch $(seq -f "file-%g.txt" 1 10)

This command creates files named file-1.txt, file-2.txt, …, file-10.txt.

2. Using seq in Loops

The seq command is often used in scripting to iterate over a sequence of numbers.

Example: For Loop

[root@server seq]# for i in $(seq 1 10); do echo "Hello $i"; done
Hello 1
Hello 2
Hello 3
Hello 4
Hello 5
Hello 6
Hello 7
Hello 8
Hello 9
Hello 10

Why Use the seq Command?

The seq command is a powerful tool for automation, especially when working with repetitive tasks. Its practical applications include:

• Creating files with sequential names.
• Looping through a set of values in scripts.
• Generating data for testing.

Learn More

For a complete list of options and details, refer to the man page.