GNU Parallel is a powerful tool that can help you automate and streamline your workflow by running jobs in parallel on a cluster of computers. However, to get the most out of this tool, it is important to understand how to achieve "tee" behavior in GNU Parallel. In this article, we will explain what tee behavior is and how you can achieve it in GNU Parallel.
What is Tee Behavior?
Tee behavior is a way to save the output of a command to a file, while also displaying it on the screen. The name comes from the shape of the "T" character, which represents the way the output is split and sent to two different places. In GNU Parallel, tee behavior is achieved using the --tee option.
How to Achieve Tee Behavior in GNU Parallel
To achieve tee behavior in GNU Parallel, you need to use the --tee option followed by the name of the file you want to save the output to. For example, the following command will run the ls command in parallel on 4 CPUs, and save the output to a file called output.txt, while also displaying it on the screen:
parallel --tee output.txt ls ::: {1..4}
In this example, the {1..4} is used to specify the range of CPUs to run the command on. You can replace this with any list of CPUs or job slots that you want to use. The output of the command will be saved to the output.txt file, and will also be displayed on the screen.
You can also use the --line-buffer option to display the output of the command on the screen as it is being written to the file. This can be useful if you want to see the output of the command in real-time. For example, the following command will run the ls command in parallel on 4 CPUs, and save the output to a file called output.txt, while also displaying it on the screen in real-time:
parallel --line-buffer --tee output.txt ls ::: {1..4}
Tee Behavior with Multiple Commands
You can also use tee behavior with multiple commands in GNU Parallel. To do this, you need to use the --pipe option to pipe the output of one command to another. For example, the following command will run the ls command in parallel on 4 CPUs, and then pipe the output to the grep command to filter the results. The output will be saved to a file called output.txt, while also being displayed on the screen:
parallel --tee output.txt ls | grep "file" ::: {1..4}
In this example, the ls command is run in parallel on 4 CPUs, and the output is then piped to the grep command, which filters the results to only show files that contain the word "file". The output of the grep command is then saved to the output.txt file, while also being displayed on the screen.
Tee behavior is a powerful feature of GNU Parallel that allows you to save the output of a command to a file, while also displaying it on the screen. By using the --tee option, you can easily achieve tee behavior in GNU Parallel, and take advantage of the many benefits it has to offer. Whether you are running a single command or multiple commands, tee behavior can help you streamline your workflow and get more done in less time.
References
| Title | Author | Link |
|---|---|---|
| GNU Parallel - Invoking GNU Parallel | Ole Tange | https://www.gnu.org/software/parallel/man.html#Invoking-GNU-Parallel |