Source: https://crashingdaily.wordpress.com/2008/03/06/diff-two-stdout-streams/
You can diff
two commands stdout without creating two files. <( ... )
command creates a temporary file with the stdout of the command inside it.
Example:
diff -B <( ls -1 / ) <( ls -1 ~ )
<( ... )
enables you to use any stdout as a "file" input to commands that need to work on files (like diff
does).