tee command reads from the standard input and writes to both standard output and one or more files at the same time.
tee is mostly used in combination with other commands through piping.
In this tutorial, we’ll cover the basics of using the
tee Command Syntax
The syntax for the
tee command is as follows:
tee [OPTIONS] [FILE]
--append) - Do not overwrite the files instead append to the given files.
--ignore-interrupts) - Ignore interrupt signals.
tee --helpto view all available options.
FILE_NAMES- One or more files. Each of which the output data is written to.
How to Use the
The most basic usage of the
tee command is to display the standard output (
stdout) of a program and write it in a file.
In the following example, we are using the
df command to get information about the amount of available disk space on the file system. The output is piped to the
tee command, which displays the output to the terminal and writes the same information to the file
df -h | tee disk_usage.txt
Filesystem Size Used Avail Use% Mounted on dev 7.8G 0 7.8G 0% /dev run 7.9G 1.8M 7.9G 1% /run /dev/nvme0n1p3 212G 159G 43G 79% / tmpfs 7.9G 357M 7.5G 5% /dev/shm tmpfs 7.9G 0 7.9G 0% /sys/fs/cgroup tmpfs 7.9G 15M 7.9G 1% /tmp /dev/nvme0n1p1 511M 107M 405M 21% /boot /dev/sda1 459G 165G 271G 38% /data tmpfs 1.6G 16K 1.6G 1% /run/user/120
You can view the content of the
disk_usage.txt file using the cat command.
Write to Multiple File
tee command can also write to multiple files. To do so, specify a list of files separated by space as arguments:
command | tee file1.out file2.out file3.out
Append to File
By default, the
tee command will overwrite the specified file. Use the
--append) option to append the output to the file:
command | tee -a file.out
To ignore interrupts use the ``-i
) option. This is useful when stopping the command during execution withCTRL+C
and wanttee` to exit gracefully.
command | tee -i file.out
Hide the Output
If you don’t want
tee to write to the standard output, you can redirect it to
command | tee file.out >/dev/null
Using tee in Conjunction with sudo
Let’s say you want to write to a file that is owned by root as a sudo user. The following command will fail because the redirection of the output is not performed by sudo. The redirection is executed as the unprivileged user.
sudo echo "newline" > /etc/file.conf
The output will look something like this:
bash: /etc/file.conf: Permission denied
sudo before the
tee command as shown below:
echo "newline" | sudo tee -a /etc/file.conf
tee will receive the output of the echo command, elevate to sudo permissions and write to the file.
tee in conjunction with
sudo allows you to write to files owned by other users.
tee command reads from standard input and writes it to standard output and one ore more files.
If you have any questions or feedback, feel free to leave a comment.