Question

I just want to know the difference between:

sort < output

and

sort output

in Linux. How does it work exactly?

Answer 1

This has been discussed on unix.stackexchange here: Performance difference between stdin and command line argument

In sort < file the shell performs redirection. It opens the file and passes the stdin file descriptor to the sort command which reads it.

In sort file, the sort command opens the file and then reads it.