Linux Beginner Note nine: Linux I/O management, redirection and plumbing! (Video serial number: 04_3)

commands to learn in this section:TR,TEE,WC

Skills learned in this section:

The composition of the computer

I/O Management and redirection

Use of pipelines

　

Knowledge Point nine: Management and IO redirection (4_3)

Computer composition:

Arithmetic, controller: CPU

Memory: RAM

Input device/Output device

　　Programs: Directives and data

Controller: reads the instruction and reads the operation and data to be performed under the control of the instruction

The arithmetic device:

Memory:

Address bus: Memory addressing

Data bus: Transferring data

Control Summary: Control command data

Register: CPU Ephemeral memory

I/O: (e.g. hard disk, monitor, mouse, etc.)

Input device: Enter device

Output device: Export device

　　System default Device Settings:

Default output device: Standard output, STDOUT, 1

Default input device: standard input, STDIN, 0

Standard error Output: STDERR, 2 (with a different data stream)

Standard input: Keyboard

Standard output and Error output: Display

I/O redirection:

Linux:

　　　: Output REDIRECT symbol:

: Overwrite output

>>: Append output

SET-C: Prohibit overwrite redirection for already existing files;

Force overwrite output, use >|

Set +c: Turn off the above features

　　　　2>: Redirect Error output

2>>: Append method

　　　　&>: Redirect standard output or error output to the same file.

　　　　<: Enter REDIRECT symbol:

' A- z ' ' A- z ' </etc/profile

　　　　<<:here document to generate documents here

cat << endthe first line,the second line. ENDcat >>/etc/myfile.txt <<eofthe first line,the second line. EOFCat /etc/myfile.txt

Pipeline:

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

Format: Command 1 | Command 2 | Command 3 | ...

--Pipe Echo'Hello Word'Echo'Hello Word'| Tr'A- z' 'A- z'--turn Hello word into uppercase and outputEcho'Redhat'| passwd--stdin hivecut-D:-f1/etc/passwd | Sort | Tr'A- z' 'A- z'--Sort the user name (1 columns) of the passwd file and turn it into uppercasels/var | Tr'A- z' 'A- z'----------------Tee reads data from standard input and sends to standard output and file echo"Hello Word"| tee/tmp/hello.out--Send Hello Word to standard output and save in file----------------WC--displays the number of rows of a file WC-L/ETC/PASSWD--not only shows the number of lines of the file but also the filename WC-l/etc/passwd | Cut-d' '-F1--implements the Cat/etc/passwd | WC-L--displays the number of rows in the directory LS/usr/bin | Wc-l

After-school assignments:

Practice:1. Statistical/usr/bin/the number of files in the directory;#Ls/usr/bin | wc-l2, the shell of all the users on the current system is removed, and each shell is displayed only once, and is displayed sequentially;#cut-d:-f7/etc/passwd | sort-u3, thinking: How to display/var/What is the content type of each file in the log directory? #file/var/log/*#cd/var/log/| file ' ls/var/log/'4. Remove/etc/the 6th line of the Inittab file;#head-6/etc/inittab | tail-15. Take out the user name and shell of the 9th user in the/etc/passwd file, display it to the screen and save it to/tmp/the users file;#tail-9/etc/passwd | head-1 | cut-d:-f1,7 | tee/tmp/users6. Display/all files beginning with PA in the ETC directory, and count the number of them;#ls-d/etc/pa* | wc-l7, do not use a text editor, will alias Cls=The clear line is added to the current user's. bashrc file;#echo "Alias Cls=clear" >> ~/.BASHRC

Linux Beginner Note nine: Linux I/O management, redirection and plumbing! (Video serial number: 04_3)