Shell---Data flow redirection

Data Flow redirection: is a command that should appear on the screen after the data transfer to other places.

Standard input (stdin): code 0, using < or <<;

Standard output (STDOUT): Code 1, using > or >>;

Standard error Output (STDERR): Code 2, using 2> or 2>>

One: Standard output

>:1 file does not exist will be automatically created

2 file exists, empty the file first, then write the data to

3 If the content already exists in the file, overwrite the contents of the file (if you do not want to overwrite it, use >> append to the original text)

Two: standard error output

2>: Output the wrong data to a specified file or device in an overridden manner

2>>: The incorrect data is output to the specified file or device in an additive way

>list_right 2>list_error

Attention:

1:/dev/null Garbage bin Black hole

How to filter out error messages and output the correct information??

#find/home-name. BASHRC  2>/dev/null

2: How to write the correct error message to the same file??

#find/home-name  >list   2>&1/home-name &> List 

Both of these methods can be

Three: Standard input

The simplest way to do this is to change the way the keyboard input is used instead of the file content.

Cat >   a   <    /root/b

Writes the contents of B to a

Shell---Data flow redirection