The tee command

The tee command in Unix (and other platforms [^1])

The tee command copies standard input to standard output and also to any files given as arguments.

&emdash; GNU documentation

If the file being written to does not already exist, it is created. If the file exists its data is overwritten unless the -a option is used.

It's interesting that the command is named after a T splitter used in plumbing.


One of the commands in the setup of a local environment for web platform tests has the tee command.

./wpt make-hosts-file | sudo tee -a /etc/hosts

The output of ./wpt make-hosts-file is output to the console and also written to /etc/hosts but without overwriting the data already in that file.

[^1]: Wikipedia says the command is available on DOS, WIndows and ReactOS.