`tee` Copy input to a file and to the screen

Reads standard input and writes it to standard output and to one or more files at the same time. Use it to save the output of a command without losing sight of it, or to save a result partway along a pipeline.

Synopsis

COMMAND | tee [-ai] FILE...
COMMAND | tee -a FILE

Common options

Option or form	What it does
`-a`	Append to the file instead of overwriting it
`-i`	Ignore the interrupt signal (Ctrl-C), so tee finishes writing
`FILE...`	Not a flag. One or more files to write to. Several files get identical copies

Examples

Show output and save it too

echo hello | tee out.txt

hello

Add a line to the end of a file

echo again | tee -a out.txt

again

Save an intermediate result and keep the pipeline going

sort words.txt | tee sorted.txt | uniq

apple
fig
pear

Write the same output to two files

ls docs | tee one.txt two.txt

old
readme.md

Capture errors as well as normal output

ls missing.txt notes.txt 2>&1 | tee result.txt

Write to a file that needs root

echo '127.0.0.1 test.local' | sudo tee -a /etc/hosts

Notes

tee overwrites existing files by default. Add -a to append, or you lose what was there.
sudo echo text > /etc/file fails because the redirect is done by your shell, not by sudo. Use echo text | sudo tee /etc/file instead. Add -a to append.
tee sends its output to the screen too. Add > /dev/null after it, as in sudo tee file > /dev/null, to keep the screen quiet.
tee only sees standard input. To capture a command's error messages, redirect them first with 2>&1, as in the example above.
The exit status of a pipeline is that of its last command. If tee is last, a failure earlier in the pipeline is hidden.

tee Copy input to a file and to the screen

Synopsis

Common options

Examples

Notes

See also

`tee` Copy input to a file and to the screen