What is Redirection?
Redirection is a feature in Linux such that when executing a command, you can change the standard input/output devices. The basic workflow of any Linux command is that it takes an input and give an output.
- The standard input (stdin) device is the keyboard.
- The standard output (stdout) device is the screen.
With redirection, the above standard input/output can be changed.
也就是说我们输出可以重定向到文件，输入不用依靠键盘手动输入，而是重定向到文件输入程序所要的参数；那最重要的就是，我们可以自动化啦
不谈输出重定向(>>,>),那是因为认识了输入重定向
"<"符号是用于输入重定向的
