Process substitution a form of inter-process communication that allows the input or output of a command to appear as a file (such as: `<(cmd)` or `>(cmd)`).

In bash manual we can read:

Process substitution is supported on systems that support named pipes (FIFOs) or the /dev/fd method of naming open files. It takes the form of <(list) or >(list). The process list is run with its input or output connected to a FIFO or some file in /dev/fd.


diff <(sort file1) <(sort file2)

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