Use tee Command for Redirecting Terminal Outputs

The tee command is a fundamental tool for Linux users. This command allows you to capture and manipulate the output of other commands and redirect it in various ways. This makes it a powerful tool for logging, debugging, and scripting. In this article, we’ll explore the basics of the tee command, its practical use cases, and some tips to help you get the most out of it.

Prerequisites

Before diving into the tee command, it’s important to have a basic understanding of Linux commands and the terminal. Familiarity with pipes and redirection will also be helpful.

Understanding the Linux Tee Command

The tee command takes the standard output of a command and writes it to a file while also sending it to the standard output. This allows you to see the output of a command on your terminal while also saving it to a file. Here’s a simple example:

$ ls -l | tee file.txt

In this example, the output of the ls -l command is written to both the terminal and to a file named file.txt.

The tee command also accepts a number of options that allow you to customize its behavior. For example, the -a option appends the output to an existing file rather than overwriting it:

$ ls -l | tee -a file.txt

Practical Use Cases

The tee command has a variety of practical uses. Here are some of the most common:

Debugging

When you’re debugging a script or program, it can be useful to log its output to a file. The tee command makes this easy by allowing you to capture the output of a command and save it to a file. For example:

$ my-script.sh 2>&1 | tee my-script.log

In this example, the output of the my-script.sh script is sent to both the terminal and a file named my-script.log.

Logging

The tee command is also useful for logging the output of a long-running command. For example:

$ ping google.com | tee ping.log

In this example, the output of the ping command is written to both the terminal and a file named ping.log.

Scripting

The tee command is also useful in shell scripts. For example, you can use it to write the output of a command to a file and email the contents of the file to someone. Here’s an example:

$ my-script.sh | tee my-script.log | mail -s "My script results" me@itvraag.nl

In this example, the output of the my-script.sh script is written to both a file named my-script.log and sent via email.

Tips for Using the Linux Tee Command

Here are some tips to help you get the most out of the tee command:

1. Use the a option to append the output to an existing file rather than overwriting it.
2. Use the > operator to redirect output to a file if you only want to save the output to a file and don’t need to see it on your terminal.
3. Use the 2>&1 operator to include both standard output and standard error in your log.
4. Use the tee command in combination with other commands to create powerful scripts and pipelines.
5. Be careful when using the tee command with sensitive information to ensure that the information is secure.

Conclusion

The tee command allows you to capture and manipulate the output of other commands and redirect it in various ways. With its practical use cases and its ability to be used in combination with other commands, the tee command is an essential tool for logging, debugging, and scripting.

For further reading, check out our articles on pipes and redirection, and the Linux terminal. As a challenge, try using the tee command in combination with other commands to create a script that logs the output of a long-running command.