Learn Linux Shell Scripting - Fundamentals of Bash 4.4

Process substitution

Something closely related to command substitution is process substitution. The syntax is as follows:

<(command)

It works very similarly to command substitution, but instead of sending the output of a command as a string somewhere, you can reference the output as a file. This means that some commands, which do not expect a string but instead a reference to a file, can be used with dynamic input as well.

While too advanced to discuss in great detail, here's a simple example that should get the point across:

reader@ubuntu:~/scripts/chapter_12$ diff <(ls /tmp/) <(ls /home/)1,11c1< directory-file< grep-file< grep-file-stdout< passwd< shadow---> reader

The diff command normally compares two files and prints their differences. ...