tee Command
Intermediate Text Processing man(1)Read from stdin and write to stdout and files
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📅 Updated: Apr 29, 2026
SYNTAX
tee [OPTION]... [FILE]...
What Does tee Do?
The tee command reads from standard input and writes to both standard output and one or more files simultaneously. Named after the T-splitter used in plumbing, it splits the output stream so you can save a copy while also passing data to the next command in a pipeline.
tee is essential when you need to both see output on screen and save it to a file, or when you need to capture intermediate pipeline results without breaking the pipeline flow.
Common use cases include logging command output while watching it in real-time, writing to files that require sudo permissions (via sudo tee), and creating pipeline taps for debugging complex data processing chains.
tee is essential when you need to both see output on screen and save it to a file, or when you need to capture intermediate pipeline results without breaking the pipeline flow.
Common use cases include logging command output while watching it in real-time, writing to files that require sudo permissions (via sudo tee), and creating pipeline taps for debugging complex data processing chains.
Options & Flags
| Option | Description | Example |
|---|---|---|
| -a | Append to files instead of overwriting | echo "new entry" | tee -a log.txt |
| -i | Ignore interrupt signals (SIGINT) | long_command | tee -i output.log |
| --output-error | Set behavior on write error (warn, exit, etc.) | command | tee --output-error=warn output.log |
| multiple files | Write to multiple files simultaneously | command | tee file1.txt file2.txt |
| /dev/null | Discard stdout while keeping file output | command | tee output.log > /dev/null |
| >(cmd) | Process substitution — send to another command | command | tee >(grep ERROR > errors.log) |
Practical Examples
#1 Save and display output
Shows the directory listing on screen AND saves it to a file.
$ ls -la | tee directory_listing.txt#2 Append to log file
Appends a timestamped message to the log file while displaying it.
$ echo "Deploy complete at $(date)" | tee -a deploy.log#3 Write to protected file with sudo
The standard way to append to root-owned files. sudo echo > file does NOT work.
$ echo '127.0.0.1 mysite.local' | sudo tee -a /etc/hosts#4 Save intermediate pipeline result
Captures raw and filtered data at different stages of the pipeline.
$ cat access.log | tee raw.log | grep 'ERROR' | tee errors.log | wc -l
Output:
42
#5 Write to multiple files
Writes the same output to three files simultaneously.
$ date | tee file1.txt file2.txt file3.txt#6 Log command output silently
Saves all output (including errors) to build.log without displaying on screen.
$ make build 2>&1 | tee build.log > /dev/nullTips & Best Practices
sudo tee for root files: Use echo "content" | sudo tee /etc/file instead of sudo echo "content" > /etc/file. The redirect runs as your user, not root.
Capture stderr too: To capture both stdout and stderr: command 2>&1 | tee output.log. This redirects stderr to stdout before tee.
Overwrite by default: tee overwrites files by default. Always use -a (append) for log files to avoid losing previous content.
Frequently Asked Questions
How do I save command output to a file AND see it on screen?
Pipe through tee: command | tee output.txt. Use -a to append instead of overwrite.
Why use tee instead of redirection?
Redirection (>) sends output only to a file, not to the screen. tee sends to both. Also, sudo tee works for root-owned files while sudo > does not.
How do I write to a file as root?
Use echo 'content' | sudo tee /path/to/file. This is the correct way because the redirect in sudo echo > file runs with user permissions, not root.
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