<> One ,Linux brief introduction
* Linux The core was originally built by Linus the Finn · Towaz （Linus Torvalds） Written out of personal interest at the University of Helsinki
* Linux Is a set of free use and free dissemination classes Unix operating system , Is based on POSIX and UNIX Multiple users of , Multitask , Support for multithreading and multithreading CPU Operating system of
* Linux Able to run the main UNIX Tool software , Application and network protocols . It supports 32 Bitwise sum 64 Bit hardware .Linux Inherited Unix
Design idea with network as the core , It is a multi-user network operating system with stable performance
because Linux Open source and other characteristics , There are many popular versions on the market now , The more well-known releases are ：Ubuntu,RedHat,CentOS,Debian,Fedora,SuSE,OpenSUSE,Arch
<> Two ,Linux basic operation
<> Normal user login
Enter the password to log in to the ordinary user
<> Super user login
Click here to enter the user name of the super user first root, Enter the password again to log in successfully , In the learning stage, we usually need super users
shell It's also a software in the operating system , It's wrapped in linux Outside the kernel , Provides an interface for the interaction between the user and the kernel , Command in the system shell To explain ,shell
Receive the output of the system response and display it on the screen
Bash (GNU Bourne-Again Shell) It's a lot Linux Default for distribution Shell, Right click on the system desktop to open bash
<> stay shell Execute command in
The command must be entered at the prompt , How to input commands ： command parameter target , Parameters and passwords are not required , Common command line prompts are
* [kiosk@foundation0 Desktop]$
* kiosk function bash Users of
* foundation0 bash Host short name
* @ Information separator
* Desktop Current default operation directory
* # Represent superuser
* $ User identity prompt
<> Test some simple commands
namely list Abbreviation of , adopt ls Commands can not only be viewed linux Files in folder , And you can view file permissions ( Include catalog , folder , file right ) View catalog information, etc .
Common parameter collocation ：
ls -a List all files in the directory , Include with . Start hidden file ls -A List Division . and .. Other documents of ls -r Reverse order ls -t Sort by file modification time ls -S
Sort by file size ls -h Display in readable size ls -l In addition to the filename , Also permissions for files , owner , File size and other information are listed in detail
cd(changeDirectory) Command syntax ：
cd [ Directory name ]
explain ： Switch current directory to dirName.
（1） Enter the desired directory
（2） get into “home” catalog
（3） Enter last working path
（4） Take the parameters of the last command as cd Parameter usage .
pwd Command to view the current working directory path .
（1） View current path
（2） View the actual path of the soft link
mkdir Command to create a folder .
Available options ：
* -m: Set access to new directory , It can also be used chmod Command settings ;
* -p: Can be a path name . At this time, if some directories in the path do not exist , With this option added , The system will automatically create directories that are not yet available , That is, multiple directories can be created at one time .
（1） The name created in the current working directory is t Folder for
（2） stay tmp The path created under the directory is test/t1/t Contents of , If not , Then create ：
mkdir -p /tmp/test/t1/t
Delete one or more files or directories in a directory , If not used -r option , be rm Directory will not be deleted . If using rm To delete a file , You can usually still restore the file to its original state .
rm [ option ] file …
（1） Delete any .log file , Ask for confirmation one by one before deleting ：
rm -i *.log
（2） delete test Delete all files in subdirectory and subdirectory , And you don't have to confirm one by one ：
rm -rf test
（3） Delete to -f File at the beginning
rm -- -f*
Remove one or more subdirectory entries from a directory , You must also have write access to the parent directory when deleting a directory .
be careful ： Cannot delete non empty directory
When parent If the subdirectory is deleted to make it an empty directory , Delete by the way ：
rmdir -p parent/child/child11
Move or change file name , According to the second parameter type （ Such as table of contents , Move file ; If it is a file, command it again ）.
When the second parameter is directory , Multiple files can be separated by spaces as the first parameter , Move multiple files to parameters 2 In the specified directory .
（1） File test.log Rename to test1.txt
mv test.log test1.txt
（2） File log1.txt,log2.txt,log3.txt Move to root test3 In the catalog
mv log1.txt log2.txt log3.txt /test3
（3） File file1 Renamed file2, If file2 Already exists , Ask if you want to overwrite
mv -i log1.txt log2.txt
（4） Move all files under the current folder to the previous directory
mv * ../
Copy source file to destination file , Or copy multiple source files to the destination directory .
be careful ： Command line copy , If the target file already exists, you will be prompted whether to overwrite it , And in shell In script , If not -i parameter , Will not prompt , It's direct coverage !
-i Tips -r Copy directory and all items in the directory -a The time of the copied file is the same as that of the original file
copy a.txt reach test Directory , Time to keep original documents , If there is a prompt in the original file, do you want to overwrite it .
cp -a a.txt test
Show entire file , Note that this command does not display directories
<>10, --help Help command
<>11,date Display current system time
```shell [root@localhost Desktop]# date '+%c' Sat 10 Aug 2019 10:32:38 PM PDT
[root@localhost Desktop]# date '+%D' 08/10/19 [root@localhost Desktop]# date
'+%x' 08/10/2019 [root@localhost Desktop]# date '+%T' 22:33:51 [root@localhost
Desktop]# date '+%X' 10:34:04 P ```
<>12,cal Display the calendar of the current month by default
less And more similar , But use less You can browse files at will , and more Move forward only , But can't move back , and less The entire file will not be loaded until it is viewed .
Common command parameters ：
-i Ignore case when searching -N Show line numbers for each line -o < file name > take less The output is saved in the specified file -s Show a row of consecutive empty lines
/ character string ： Search down “ character string ” Function of ? character string ： Search up “ character string ” Function of
View multiple files
less 1.log 2.log
have access to n View next , use p View previous .
head Used to display the beginning of a file to standard output , default head Command to print the beginning of its corresponding file 10 That's ok .
Common parameters ：
-n< Number of rows > Number of lines displayed （ The number of lines is complex, indicating the number from the last to the front ）
（1） display 1.log Before in file 20 That's ok
head 1.log -n 20
（2） display 1.log Before document 20 byte
head -c 20 log2014.log
（3） display t.log last 10 That's ok
head -n -10 t.log
Used to display the content at the end of the specified file , When no file is specified , Process as input . Common view log files .
Common parameters ：
-f Circular reading （ Commonly used to view incremental log files ） -n< Number of rows > Show rows （ Back to front ）
display filename last 20 That's ok .
tail -n 20 filename
<> Three ,SHELL Historical calls in
* history Show history
* Up down key Search history one by one
* ! number Call this number history
* ! letter Call recent history starting with this letter
* ctrl+r+ keyword Call the latest history with this keyword
* history -c Clear current shell History in
<> Four , Common shortcut keys in the current system