# How to Use Tee on Linux

By Zubair Ahmed · Published 2020-11-08
Source: https://www.grizzlybit.dev/blog/how-to-use-tee-on-linux

## What is tee?

`tee` on Linux is a command-line tool, it reads from the standard input and is the capability of writing results to the terminal's standard output and files at the same time. This essentially lets you store and view (both at the same time) the output at any time.

## How to use it?

Let's illustrate the use of `tee` with a simple example. We can use a command to ping `[google.com](http://google.com)`

```bash
ping google.com
```

The output should be displayed only on your screen which is standard output (STDOUT):

![log standard output to screen](https://www.grizzlybit.dev/blog/how-to-use-tee-on-linux/ping.png)

Now, let's try and write the output to a file:

```bash
ping google.com > ~/ping.log
```

Now, your screen will pretty much be blank and the output will be writing to the file mention on the path `~/ping.log`:

![Log standard output to file](https://www.grizzlybit.dev/blog/how-to-use-tee-on-linux/ping-to-file.png)

```bash
# ~/ping.log
PING google.com (142.250.67.78): 56 data bytes
64 bytes from 142.250.67.78: icmp_seq=0 ttl=116 time=12.489 ms
64 bytes from 142.250.67.78: icmp_seq=1 ttl=116 time=9.979 ms
64 bytes from 142.250.67.78: icmp_seq=2 ttl=116 time=10.664 ms
64 bytes from 142.250.67.78: icmp_seq=3 ttl=116 time=8.961 ms
64 bytes from 142.250.67.78: icmp_seq=4 ttl=116 time=9.497 ms
64 bytes from 142.250.67.78: icmp_seq=5 ttl=116 time=9.856 ms
64 bytes from 142.250.67.78: icmp_seq=6 ttl=116 time=10.083 ms
64 bytes from 142.250.67.78: icmp_seq=7 ttl=116 time=9.735 ms
64 bytes from 142.250.67.78: icmp_seq=8 ttl=116 time=9.066 ms
```

Now, we will `tee` to do both at the same exact time:

```bash
ping google.com | tee ~/ping.log
```

The output this time around will be written to the screen as well as the file:

![Log standard output to screen and file using tee](https://www.grizzlybit.dev/blog/how-to-use-tee-on-linux/ping-using-tee.png)

```bash
# ~/ping.log
PING google.com (142.250.67.78): 56 data bytes
64 bytes from 142.250.67.78: icmp_seq=0 ttl=116 time=9.486 ms
64 bytes from 142.250.67.78: icmp_seq=1 ttl=116 time=11.808 ms
64 bytes from 142.250.67.78: icmp_seq=2 ttl=116 time=9.171 ms
64 bytes from 142.250.67.78: icmp_seq=3 ttl=116 time=13.124 ms
64 bytes from 142.250.67.78: icmp_seq=4 ttl=116 time=9.766 ms
64 bytes from 142.250.67.78: icmp_seq=5 ttl=116 time=9.446 ms
64 bytes from 142.250.67.78: icmp_seq=6 ttl=116 time=11.303 ms
64 bytes from 142.250.67.78: icmp_seq=7 ttl=116 time=11.421 ms
64 bytes from 142.250.67.78: icmp_seq=8 ttl=116 time=9.201 ms
64 bytes from 142.250.67.78: icmp_seq=9 ttl=116 time=9.372 ms
64 bytes from 142.250.67.78: icmp_seq=10 ttl=116 time=10.267 ms
```

So, essentially, the command has the following format:

```bash
tee [OPTION]... [FILE]...
```

And quite plainly the `man` page explains it as:

> > The tee utility copies standard input to standard output, making a copy in zero or more files. The output is unbuffered.

## More Options

As you might have stumbled on the `man` page already, there are more options that can be fed to our `tee` command. Some of them are:

## Append

By default `tee` command overwrites the file. You can append to the file by using the `-a` option as shown below:

```bash
ping google.com | tee -a ~/ping.log
```

## Write to Multiple Files

You can write to multiple files by just specifying the names or directories of the files:

```bash
ping google.com | tee -a file1 file2 file3
```

## Conclusion

I think we can all agree that `tee` is one delightful Linux command. The tool definitely is quite easy to use and has a little-to-no learning curve. But you can always view its `man` page at any time to know further information.

Happy Grizzly Coding! 🐻