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Using the `tee` Command - Read From `stdin`, Ouput to `stdout` and Files

The tee command in Linux is a versatile utility often employed to read from standard input and write to standard output and files simultaneously. It is named after the T-splitter used in plumbing systems that equally divides the flow. In computing, tee works similarly by taking the data from standard input (stdin) and duplicating it into two different directions: to standard output (stdout) and one or more files.


The general syntax for the tee command is:

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

Here [OPTION] is optional, and it specifies how the tee command should behave, while [FILE] denotes the files where the content should be saved.

Options Table

--append-aAppend to the given files, do not overwrite them.
--ignore-interrupts-iIgnore interrupt signals.
--helpDisplay the help message and exit.
--versionDisplay the version information and exit.

Basic Usage

Lets create a file called input.text

Creating input.text file
This is line 1
This is line 2
This is line 3

Write to a File and Standard Output

The most straightforward use case for tee is writing data to a file and the terminal simultaneously.

For example, the following command will copy the content of input.txt to output.txt while also displaying the content on the terminal:

cat input.txt | tee output.txt

Append to a File and Standard Output

To append the data to an existing file rather than overwriting it, use the -a or --append option.

echo "This is a new line" | tee -a output.txt

This will append the line "This is a new line" to output.txt and display it on the terminal.

Ignore Interrupts

If you want to make tee ignore interrupt signals (like Ctrl+C), use the -i or --ignore-interrupts option:

cat input.txt | tee -i output.txt

Advanced Usage

Writing to Multiple Files

tee allows you to write to multiple files at the same time. Simply specify the filenames separated by spaces:

echo "Multifile Example" | tee file1.txt file2.txt file3.txt

Combining Multiple Options

Options can be combined for more specific functionality. To write to multiple files and append to them:

echo "Appending to multiple files" | tee -a file1.txt file2.txt

Using tee with Other Commands

tee is commonly combined with other commands to enable various workflows. One such example is using tee with sudo to write to files owned by the root:

echo "new content" | sudo tee -a /etc/some_config_file > /dev/null

Here, > /dev/null suppresses the output to the terminal but still allows tee to append "new content" to a system file that needs root permissions.


The tee command is a simple but powerful tool for duplicating data streams in a shell pipeline. Its ability to write or append data to one or more files while also sending it to standard output makes it incredibly useful in scripting and day-to-day tasks. Understanding the options and combinations can help you use this command more effectively.

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