Bash: Repeated tasks with seq and for loops

There comes a time where every sysadmin needs to execute the same task multiple times. Whether you need to create 12,000 2MB files, create multiple users, or simply delete more then 50k files at a time; for loops will save you time and typing.

For the instances where you need to execute a for loop a specific amount of times you can use seq to your advantage.

Today's example will show you how to create multiple files.

Example:

[email protected]:~$ for x in `seq 1 1 10`; do touch test.$x.txt; done  
[email protected]:~$ ls -la test.*  
-rw-r--r-- 1 bcane bcane 0 2011-08-03 14:31 test.10.txt  
-rw-r--r-- 1 bcane bcane 0 2011-08-03 14:31 test.1.txt  
-rw-r--r-- 1 bcane bcane 0 2011-08-03 14:31 test.2.txt  
-rw-r--r-- 1 bcane bcane 0 2011-08-03 14:31 test.3.txt  
-rw-r--r-- 1 bcane bcane 0 2011-08-03 14:31 test.4.txt  
-rw-r--r-- 1 bcane bcane 0 2011-08-03 14:31 test.5.txt  
-rw-r--r-- 1 bcane bcane 0 2011-08-03 14:31 test.6.txt  
-rw-r--r-- 1 bcane bcane 0 2011-08-03 14:31 test.7.txt  
-rw-r--r-- 1 bcane bcane 0 2011-08-03 14:31 test.8.txt  
-rw-r--r-- 1 bcane bcane 0 2011-08-03 14:31 test.9.txt  

Why it works

The command seq will output numbers based on the criteria you give it. The first number you provide seq is the number you want to start with, the second is the number you want to increment by. For example if you put seq 1 2 10 you would get an output of 1, 3, 5, 7, & 9. The last number in the list is the number you want to end with, as you can see from my 1 2 10 example if 10 is not the last number in the increment it will stop on the number before.

[email protected]:~$ seq 1 2 10  
1  
3  
5  
7  
9  
[email protected]:~$ seq 1 1 10  
1  
2  
3  
4  
5  
6  
7  
8  
9
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Benjamin Cane
Principal Engineer, Vice President

Benjamin Cane is Principal Engineer at American Express. He has more than 16 years of experience with roles in both systems and software engineering. He leverages both his systems and software skills to build end-to-end platforms. Platforms, purpose built for performance and resiliency. Benjamin is also the author of Red Hat Enterprise Linux - Troubleshooting Guide (2015, Packt Publishing), and he has published many popular articles on topics such as Linux, Docker, Python, Go and Performance Tuning. Thoughts and Opinions expressed in my articles are my own.

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