Redirect input, output, and pipe commands

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提示：以下是本篇文章正文内容，下面案例可供参考

1. What is redirection?

• "Redirection" is to re-change the direction of command input and output.
• The original input direction of the command is the keyboard, so this input is called standard input.
• The original output direction of the command is the display, so this output is called standard output.

2. Redirect command

1. Redirect output command

Command format:
a command with output results > file name

Function description:

• Direct the output of this command to a file.
• The command must have an output before it can be placed before ">".
  Demo:

2. Redirect input command

Command format:
a command that needs to input data from the keyboard < file name

Function description:

• If the command needs to get one or some input data from the keyboard during execution, you can use "<" to redirect its standard input so that the input data it needs comes from a file instead of the keyboard.

Demo:

• Use the mail command to send mail to other users in the Linux system.

Use the file to improve:

3. Other commands

• "<" can be used or not

• Mixed use of redirects

instant tune

重定向混合使用需要注意的问题：

• Usage of "-"

3. Pipeline commands

Command format:
Command 1 | Command 2 | Command 3·····

Function description:

• Pass the output result of the previous command through the pipeline command "|" as the input data of the next command.
• Both sides of the pipeline command can only be commands, not files.

Function Demo:

Notes:

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