I/O redirection

Computer structure:

Arithmetic, controller: CPU

Memory: RAM

Input device/Output device

Programs: Data and instructions

Controller: Instruction

The arithmetic device:

Memory

Address bus: Intrinsic addressing
Data bus: Transmission

Control Bus: Control instructions

Register: CPU Temporary memory,

I/O devices: Hard drives, keyboards, monitors

Input device

Output device

System settings:

Default output device: Standard output, stdout,1

Default Access device: Standard input, stdin,0

Standard error Output: stderr,2 (Descriptor)

Standard input: Keyboard

Standard output and Error output: Display

i/0 redirection

Linux:> < >> <<

Set-c prohibit overwrite redirection for existing files

Force overwrite output, then use the >| method ls var >| /tmp/var.txt

+c turn off the above features

> Just output standard output

2>: Redirect Error output

2 ": Append error Output

&> redirect standard output or error output to the same file

< input redirection

The Here Document

Cat >>/tme/myfile.txt << EOF

echo "Hello World" | Tee/tmp/echo.out output to the screen and save to a copy of the file

Pipelines: Commands

Command 1| Command 2| command 3| .....

The output of the previous command, as input to the latter command

Echo ' Hello World ' | Tr ' A-Z ' A-Z

I/O redirection