Process substitution can be used to create a file descriptor from the
evaluation of a shell command. The syntax for process substitution is
LIST is one or more bash commands.
$ cat <(echo 'hello, world') hello, world
This is particularly useful for commands that expect files, such as diff:
$ diff <(echo 'hello, world') <(echo 'hello, mars') 1c1 < hello, world --- > hello, mars