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Linux Tee Command
The tee command reads from standard input and writes to both standard output and one or more files at the same time. Tee is most commonly used in combination with other commands through piping.
In this tutorial, we’ll cover the basics of using the tee command.
Tee Command Syntax
Before going into how to use the tee command, let’s start by reviewing the basic syntax:
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 being written to.
How to use Linux tee command
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 verify the content of the
disk_usage.txt file using the cat command.
Write to Multiple File
The tee command can also write to multiple files. To do so simply specify a list of files separated by space after the tee command:
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 ignores interrupts use the `
--ignore-interrupts) option. This is useful for example if you interrupt the command during execution with
CTRL+C and you want
tee to exit gracefully.
command | tee -i file.out
Hide the Output
If you don’t want
tee to write to the standard output (display output on the screen), you just need to 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, it will happen as the unprivileged user.
sudo echo "newline" > /etc/file.conf
The output will look something like this:
bash: /etc/file.conf: Permission denied
You can use the
tee command in conjunction with sudo to write to files owned by other users.
sudo before the
tee command as shown bellow:
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.
By now you should have a good understanding of how to use the Linux tee command.
If you have any question or feedback feel free to leave a comment.