The here string is the leaner, more versatile cousin of the here doc.

If you're reading this publication, you already know that Linux is one of the most powerful and versatile operating systems available today. If you're an old-timer like me, you also know all about the ...

The first line writes "hello world" to the file "output", the second reads it back and writes it to standard output (normally the terminal). A "here" document is essentially a temporary, nameless file ...