Ubuntu中文论坛

However, there is much more to redirection than this simple example reveals. You’ll learn more about the
standard file descriptors in Chapter 3, but for now all you need to know is that file descriptor 0 is the standard
input to a program, file descriptor 1 is the standard output, and file descriptor 2 is the standard error
output. You can redirect each of these independently. In fact, you can also redirect other file descriptors, but
it’s unusual to want to redirect any other than the standard ones: 0, 1, and 2.