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Shell_ 00_ First meeting shell
2022-07-06 16:50:00 【Coke loving w】
Shell_00_ First time to know Shell
Shell Basics
CLI(Command Line Interface): Command line interface
1)CLI Only accept text input , And only output text and basic graphics ;
2)Linux After system startup , Create by default in the system memory 5~6 individual CLI Terminal session running
// It can be done by Ctrl+Alt+(F2~F7) Switch ,F1 For graphical interface
Shell: Users and Linux Kernel interactive program ( be based on C Language writing )
Shell species | explain |
---|---|
csh (C Shell) | Grammatical similarity C Language , Internal orders 52 individual At present, it is not used much , Has been /bin/tcsh replaced |
Ksh (Korn Shell) | Grammatical similarity Bourne Shell, Internal orders 42 individual Have csh Easy to use features , be relative to bash A little restrictive |
tcsh | Belong to csh Enhanced Edition , And csh Fully compatible with |
sh | It belongs to shortcut Has been /bin/bash replaced |
zch | Linux The largest in Shell, Internal orders 84 individual More complex to use , Rarely use this Shell |
bash | CentOS By default, the system uses Shell |
1)bash The path of is :/bin/bash;
2) stay /etc/passwd The last field in each row is the user's default shell
Bash Shell
Bash(GNU Bourne-Again Shell): A number of Linux The default in the distribution Shell Interpreter
1) The following is from Shell Name instead of Bash Shell name ;
2)Bash Shell The essence is a program ( When running , It becomes a process )
Shell function
(1) Record historical orders (history)
1)“~/.bash_histroy” Record all commands executed by login ( Default 1000 individual );
2) The command executed by login is stored in memory , After logging off the system, the memory records it to ~/.bash_history file ;
3) The number of recorded commands can be modified HISTFILESIZE To increase / Reduce
history command : operation Shell The historical order in the book
Command format 1:histroy n
1)N Is the number , According to recent N Historical orders
2) If there is no N, Then all historical commands are displayed by default
Command format 2:history Options // Operate on historical commands
Options | meaning |
---|---|
-c | Will the current Shell All in history Content removal |
-a | Will add history Cache is written to ~/.bash_history In file |
-r | take ~/.bash_history The contents of the document read history In cache |
-w | The current history Cache is written to ~/.bash_history In file |
! command : Carry out section N History commands
Command format :!N
//!! Is to execute the last command
(2) command / File completion function (Tab)
1) Command only / Prefix of file name , adopt Tab Key can automatically complete ;
2) If there are multiple commands / The prefix of the file name is the same , Then list all specific names
(3) Command alias settings (alias)
1) To configure “~/.bashrc” File implementation command alias
alias command : Set alias command ( Temporary settings )
Command format :alias The alias command =‘ command Options ’
1) Direct input alias Then all alias commands are displayed
unalias command : Cancel command alias
Command format :unalias The alias command
(4) Programming script (shell scripts)
(5) task management 、 The front desk 、 Backstage control (job control、foreground、background)
(6) wildcard (Wilecard)
Father / Son Shell
Father Shell: Sign in CLI or GUI When running the terminal emulator in , Interaction started by default Shell
Son Shell: In the father Shell Under the environment of , New created by invoking the command Shell Program
1) Son Shell Only the father can inherit Shell The global environment variable of ;
bash command : establish / Callers Shell
Command format :bash Options
Options | meaning |
---|---|
-c command | Callers Shell After executing the specified command , And return to the parent Shell |
-i | Create a child Shell, And enter the sub Shell |
-l | With login shell Form creation sub Shell, And enter the sub Shell |
-r | Create a child Shell, And enter the sub Shell Dan Zi Shell Cannot switch directories |
exit command : sign out Shell
Command format :exit
1) if Shell Itself is a child Shell, Will return to the relative child Shell The father of Shell;
2) if Shell Itself is the highest level Shell, It will close Shell;
Such as : Callers Shell Execute the specified command
Such as : Create a child Shell, And enter the sub Shell Then return to the father Shell
Such as : Create restricted child Shell
Built in command
External command ( File system commands ):Bash Shell Outside the program
1) Usually located in /bin、/usr/bin、/sbin or /usr/sbin in ;
3) Call external command , You need to specify the absolute path of the external command ;
2) When invoking an external command , By default, create a child Shell Run external commands ;
which command : Query the full path of the command according to the command name
Command format :which Options Command name
Options | meaning |
---|---|
-a | Put all PATH The commands found in the directory are listed |
-v | Display the version information of the command |
1) The essence is based on environmental variables (PATH) The path specified , Go to query the file name
2) There are no options , The first full path found is displayed by default
Such as : Inquire about ls The full path of the command
Internal key command :Bash Shell Component part ( Compile into one )
1) The internal key command defaults to the parent Shell Run in ;
type command : Query whether the command is Bash shell Built in commands
Command format :type Options Command name
Options | meaning |
---|---|
-a | take PATH In the path of variable definition All file paths containing the command name are listed ( Include alias) |
-p | The command is an external command , Will display the full file path If it were not for external orders , Then no data is displayed |
-t | Command attributes are represented by special fields |
1)type Commands are similar in nature which command : Find the execution file
2) The special field is :file( External command )、alias( Command alias )、builtin( Internal key command )
Common internal key commands are as follows :
command | function |
---|---|
: | Extended parameter list , Perform the redirection operation |
. | Read and execute the command in the specified file |
alias | Specify the command definition alias |
bg | Run the task in background mode |
bind | Bind the keyboard sequence to a readline Function or macro |
break | Exit loop |
builtin | Execute specified Shell Built in command |
caller | Returns the context of the active subfunction call |
cd | Toggle directory |
command | Execute the specified command , Don't make Shell lookup |
compgen | Specify word generation possible completion matches |
complete | Display the specified word completion process |
compopt | Modify the completion options for the specified word |
continue | Skip this cycle , So let's do the next loop |
declare | Declare variables or variable types |
dirs | List the current storage directory |
disown | Delete the task specified in the task column |
echo | Output the specified text to stdout |
enable | Enable / Disable the specified built-in command |
eval | Splice the specified parameters into one command , And implement |
exec | Specify command substitution Shell process |
exit | mandatory Shell Exit with the specified exit status code |
export | Specify the variable as the environment variable |
fc | Select a command from the history |
fg | Transfer the task to the foreground to run |
getopts | Analyze the specified positional parameters |
hash | Query and record the full pathname of the specified command |
help | List the help documents |
history | Display the history of the command |
jobs | Make a list of tasks |
kill | To specify the PID The process signals |
let | Calculates each parameter in a mathematical expression |
local | Create a variable with limited scope in the function |
logout | sign out Shell |
mapfile | from stdin Read data row , And join the index data group |
popd | Delete record from directory stack |
printf | Displays text using a formatted string |
pushd | Add a directory to the directory stack |
pwd | Displays the path of the current working directory |
read | from stdin Read a row of data , And assign it to the specified variable |
readarray | from stdin Read data row , And put it into the index data group |
readonly | from stdin Read a row of data , And assign it to a read-only variable |
return | Force the function to exit with the specified value |
set | Sets and displays the values and values of environment variables Shell attribute |
shift | Move the position parameters in turn |
shopt | open / Close control Shell Variable value for optional behavior |
source | Read and execute the command in the specified file |
suspend | Pause Shell Implementation , Until receipt SIGCONT The signal |
test | Returns the exit status code based on the specified condition 0 or 1 |
times | Displays the accumulated user and system time |
trap | If the specified system signal is received , Then execute the specified command |
type | Detect whether it is a built-in command |
typeset | Declare variables or variable types |
ulimit | Set the specified resource limit for system users |
umask | Specify the default mask for document permissions |
unalias | Delete the specified alias |
unset | Delete the specified environment variable or Shell attribute |
wait | Wait for the specified process to complete , And return the exit status code |
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