How can you diff two pipelines in Bash?

Question

How can you diff two pipelines without using temporary files in Bash? Say you have two command pipelines:

foo | bar
baz | quux

And you wan

Answer 1

In bash you can use subshells, to execute the command pipelines individually, by enclosing the pipeline within parenthesis. You can then prefix these with < to create anonymous named pipes which you can then pass to diff.

For example:

diff <(foo | bar) <(baz | quux)

The anonymous named pipes are managed by bash so they are created and destroyed automatically (unlike temporary files).