functions.sh/doc/stacks/tiers.md

Stacking with Tiers: a How-To

Pipes in scripting are really nice.

echo 'a pipe character between two quotation marks with whitespace on either side:'
echo ' \'|\' '

We take a pipe, put a command on either side, and sometimes, we can use capabilities of both programs to do something even more useful than a single command could accomplish.

This is the underlying principle of function stacking.

echo 'stacking user feedback with a file write' | tee -a ${cache}/tutorial.log

Exercise:

Unpack & identify the parts of the above command,
what they do,
and some reasons why you might want to do them in a script.