CompTIA Linux+ XK0-005 - 3.1 - Common Script Utilities: tee

The tee command is a versatile utility in Linux that allows users to read from standard input and write to both standard output and one or more files simultaneously. It is commonly used in shell scripts and command-line pipelines to split and redirect output to multiple destinations, providing a convenient way to capture and store data while still displaying it on the screen.

In this guide, we will explore the various applications and features of the tee command, including its syntax, usage examples, and common options. Understanding the tee command will not only enhance your Linux command-line skills but also prove beneficial for the CompTIA Linux+ exam.

Syntax

The basic syntax of the tee command is as follows:

tee [OPTION]... [FILE]...

Here, [OPTION] represents the command-line options that modify the behavior of tee, and [FILE] represents one or more filenames to which the output should be written. If no file is specified, tee will create a copy of the standard input in the current directory with the filename teeoutput.

Common Options

The tee command provides a few options to modify its behavior. Here are some commonly used options:

-a or --append: Append the output to the specified file instead of overwriting it.
-i or --ignore-interrupts: Ignore interrupt signals, such as SIGINT (Ctrl+C).

Please refer to the tee command's manual page (man tee) for a complete list of options and their descriptions.

Usage Examples

Saving Command Output to a File

To save the output of a command to a file using tee, you can use the following command:

ls | tee directory_list.txt

This example executes the ls command to list the files in the current directory. The output is then redirected using tee to the file directory_list.txt, which will contain the list of files.

Appending Command Output to a File

If you want to append the output of a command to an existing file, you can use the -a or --append option. Here's an example:

date | tee -a log.txt

In this example, the date command is executed to display the current date and time. The output is then appended to the file log.txt using the tee command with the -a option. Each time the command is executed, the date and time information will be appended to the file.

Writing to Multiple Files

tee allows you to write the output to multiple files simultaneously. Simply specify multiple filenames separated by spaces. Here's an example:

echo "Hello, World!" | tee file1.txt file2.txt file3.txt

This example uses the echo command to display the string "Hello, World!" on the screen. The output is then written to three files: file1.txt, file2.txt, and file3.txt. Each file will contain the "Hello, World!" string.

Conclusion

The tee command is a powerful tool for splitting and redirecting output to multiple destinations in Linux. It allows you to save command output to files while still displaying it on the screen. By mastering the usage of tee, you can efficiently handle command output in various scenarios.

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