Named pipes
diff <(ls ./old) <(ls ./new)
This creates a virtual file with the contents of the output of ls ./old.
References
- Named pipe (wikipedia.org)
Named pipes (also known as FIFOs) are a powerful shell feature that let you redirect the output of one command to the input of another, without creating temporary files.
diff <(ls ./old) <(ls ./new)
This creates a virtual file with the contents of the output of ls ./old.