Mastering the tee Command: 7 Practical Linux Examples

The tee command is a Unix utility that reads data from standard input and writes it to one or more files while also sending the same data to standard output, making it useful for logging and chaining commands.

Example 1: Basic Usage

Display the output of lsblk and save it to devices.txt at the same time: lsblk | tee devices.txt You can verify the file content with:

cat devices.txt

Example 2: Writing to Multiple Files

Redirect the output of hostnamectl to two files simultaneously: hostnamectl | tee file1.txt file2.txt The command prints the system hostname details to the terminal and stores the same output in file1.txt and file2.txt.

Example 3: Silent Output to a File

Suppress screen output by redirecting tee’s output to /dev/null while still saving to a file:

df -Th | tee file4.txt > /dev/null

Example 4: Appending Output to a File

By default tee overwrites the target file. Use the -a or --append option to add new data without erasing existing content:

lsblk | tee file1.txt
date | tee -a file1.txt
cat file1.txt

Example 5: Using tee with sudo

When a command needs root privileges to write to a protected file, prepend sudo to tee:

echo "10.200.50.20 db-01" | sudo tee -a /etc/hosts

Example 6: Piping tee Between Commands

Chain commands by feeding tee’s output directly into another command, for instance counting lines after filtering:

grep 'root' /etc/passwd | tee /tmp/passwd.tmp | wc -l

The filtered lines are saved to /tmp/passwd.tmp and the line count is displayed.

Example 7: Using tee Inside vim

When editing a root‑owned file in vim without sudo, write the buffer through tee to gain the necessary permissions:

:w !sudo tee %

Conclusion

The tee command is a versatile tool for duplicating command output, supporting basic logging, multi‑file writes, silent operation, appending, privilege escalation with sudo, and integration into pipelines or editors like vim.