4. pipe and tee

Lesson Content

Let’s get into some plumbing now, not really but kinda. Let’s try a command:

$ ls -la /etc

You should see a very long list of items, it’s a little hard to read actually. Instead of redirecting this output to a file, wouldn’t it be nice if we could just see the output in another command like less? Well we can!

$ ls -la /etc | less 

The pipe operator |, represented by a vertical bar, allows us to get the stdout of a command and make that the stdin to another process. In this case, we took the stdout of ls -la /etc and then piped it to the less command. The pipe command is extremely useful and we will continue to use it for all eternity.

Well what if I wanted to write the output of my command to two different streams? That’s possible with the tee command:

$ ls | tee peanuts.txt

You should see the output of ls on your screen and if you open up the peanuts.txt file you should see the same information!

Exercise

Try the following commands:

$ ls | tee peanuts.txt banan.txt

Quiz Question