Linux Common commands

Modify the Initdefault parameter in the/etc/inittab file can modify the default start graphical interface or text interface, 3 is the default to enter the text interface, 5 is the default to enter the graphical interface.

Init 6

Shutdown–r now reboot

Shutdown–r delay number of minutes delay how long to restart

Shutdown

Halt

Init 0

Shutdown–h now

#是root用户

$ is a regular user

Add the user and change the password

Useradd Liuwu

PASSWD Liuwu

Delete User

Userdel–r Liuwu

Switch users

Su

Usage: su root or Su-root

The difference between the two is that Su root does not reload the user variable that switches the user, and Su-root reloads the user's user variables

Restart, start, stop network commands

Service Network Restart/start/stop

VI command

• Cursor positioning

M move cursor to center of page

L MOVE the cursor to the end of the page

H move the cursor to the beginning of the page

Ctrl+f back Page

Ctrl+b Page Forward

0 move the cursor to the beginning of the line

$ move cursor to end of line

/: From top to bottom find n next n prev

?: Find from bottom to top

• Undo and Redo

U revert to previous action-undo

. Repeat previous action-repeat

• Copy-paste Delete

Nyy the next n-line content where the cursor is copied

YW copy the words after the cursor, with spaces as the demarcation

P Paste the copied content at the cursor

NDD Delete the contents of the down N line where the cursor is located

CTRL + D: Flip down half-screen content

CTRL + U: Flip up half-screen content

Shift + G: to end of file

R: Replace the current position character

X: Delete the current position character

DD: Delete entire row

Set Number: Show line numbers

• Copy-paste Delete

Set Nonu: Suppress line numbers

: 1,3y copy first line to third row

: 1,3d Delete First row to third row

: 1,3s/str/str_new/g replaces the string from the first row to the third row (all in one row)

: 1,3s/str/str_new replaces the first character of the string in the first line to the third line

: 1,3 g/str/d Delete the line containing the string in the first row to the third row

% all,:%d all deleted

:%s/str/str_new/g Replaces all

• Search string

Enter the string/+ you want to find/bestest

Press the N key to re-locate the next

N Find Previous

• Exit VI

Q Exit VI

Q! Do not save exit

Wq Save exit

E! Do not save the modified file

W Save

！ Coercion, followed by an exclamation mark, indicates coercion.

Uname–a Viewing the system version

DF–LH show how big the hard drive is

Netstat-nlpt|grep 80 Check Port number is not occupied

|wc–l

Ps-ef|grep MySQL finds all processes, finds MySQL in the results, and displays a grep process if no MySQL

Ps-ef|grep Mysql–v Prep This ruled out grep.

• Head: Displays the beginning of the file to the standard output

Usage: head [parameter] ... [File] ...

Main parameters:

-n< rows > rows displayed

• Tail: Viewing the end of a file

Usage: tail [parameters] [file]

Main parameters:-F Dynamic Read

Dynamic View Log tail-f Err.log

View the end of 10 rows of logs tail-10 Err.log

Dynamically view the end of the 5-line log tail-5f Err.log

• WC: Counts the number of rows, bytes, and words in the specified file, and displays the results of the statistics output

Usage: WC [options] [file]

Main parameters:

-C Count bytes.

-L counts the number of rows.

-M counts the number of characters. This flag cannot be used with the-C flag.

-W count words. A word is defined as a string separated by a blank, a jump, or a newline character.

-L Prints the length of the longest line.

-HELP Display Help information

can be used without any parameters

Grep-c "foo" a.txt

Ps-ef|grep httpd |grep-v "grep"

Find/-name Besttest

awk Combat

• Line that matches the contents of the file occurrence

awk '/exception/{print NR} ' catalina.out

• Querying the Tomcat process number

Ps-ef|grep Tomcat |grep-v "grep" |awk ' {print $} '

• Output the Access IP address, access path, and status code in the Apache log

awk ' {print ' ip== "$", "path==" $7, "code==" $9} '/opt/lampp/logs/access_log

• The name of the student who failed the grade is output

awk ' {if ($2>60) {}else{print $} ' Soce.txt

• Write the MySQL process number to the Mysql.pid file.

Ps-ef|grep mysql|grep-v "grep" |awk ' {print $ > ' mysql.pid '} '

• Shell supports custom variables

Variable name does not add dollar sign ($) when defining a variable

Name= ' Besttest '

Note that there can be no spaces between the variable name and the equals sign, which may be different from all of the programming languages you are familiar with, along with the following rules:

The first character must be a letter (a-z,a-z).

You can use an underscore (_) without spaces in the middle.

Punctuation cannot be used.

You can't use the keywords in bash (you can see the reserved keywords using the help command).

Using variables, add a dollar sign ($) or ${name} before using a variable to

Echo ${name}

Variable	Meaning
$$	The current shell process ID, which is the PID of this script
$	Current file name
$n	Take the arguments passed to the script, N is a number, n is a few arguments
$#	Number of parameters to take
[Email protected]	Take all parameters, enclosed by double quotation marks (""), slightly different from $*
$*	Take all parameters
$?	Exit status of the last command, 0 means no error, and any other value indicates an error

+-*/% respectively for add, subtract, multiply, divide, withdraw

Just enclose a specific arithmetic expression in "$ ((" and ")"), for example:

a=$ ((4-2)) A has a value of 2

a=10

b=2

echo $ (($a + $b))

echo $ (($a-$b))

echo $ (($a * $b))

echo $ (($a/$b))

echo $ (($a% $b))

Operator	Description	Example
-eq	Detects whether two numbers are equal and returns true for equality.	[$a-eq $b]
-ne	Detects whether two numbers are equal and returns true if they are not equal.	[$a-ne $b]
-gt	Detects if the number on the left is greater than the right and, if so, returns True.	[$a-gt $b]
-lt	Detects if the number on the left is less than the right and, if so, returns True.	[$a-lt $b]
-ge	Detects if the number on the left is large equal to the right, and returns true if it is.	[$a-ge $b]
-le	Detects if the left number is less than or equal to the right, and returns true if it is.	[$a-le $b]

Operator	Description	Example
-D File	Detects if the file is a directory, and returns True if it is.	[-D $file] returns false.
-F File	Detects if the file is a normal file (neither a directory nor a device file), and returns True if it is.	[-F $file] returns TRUE.
-R File	Detects if the file is readable and returns true if it is.	[-R $file] returns TRUE.
-W File	Detects if the file is writable and returns true if it is.	[-W $file] returns TRUE.
-X File	Detects if the file can be executed and, if so, returns True.	[-X $file] returns TRUE.
-S file	Detects whether the file is empty (the file size is greater than 0) and does not return true for null.	[-S $file] returns TRUE.
-E File	Detects whether the file (including the directory) exists and, if so, returns True.	[-e $file] returns TRUE.

Defining arrays

In the shell, the array is represented by parentheses, the elements of the array are separated by a "space" symbol, not separated by commas in other languages, only one-dimensional arrays are supported in the shell, and the subscript of an array can be discontinuous.

For example:

Array = (value1 value2 ...)

Array = (value

Value1

value2)

An array can also be defined by assigning a value to the subscript

List[0]=1

List[8]=9

How arrays are evaluated:

${array_name[index]}

${list[0]}

Use @ or * to get all the elements in the array, such as

${list[*]}

${list[@]}

The method of getting the length of the array is the same as getting the string length, using #, for example:

Len = ${#list [*]}

• The IF statement determines which branch to execute by using relational operators to determine whether an expression is true or false. The Shell has three kinds of if ... else statements:
  • If ... fi statement;
  • If ... else ... fi statement;
  • If ... else ... elif. Fi statement.
  • Syntax for the IF ... else statement:
    • if [expression]

Then Statement (s)

Else

Statement (s)

Fi

Syntax for the IF ... elif...else...fi statement:

if [expression]

Then Statement (s)

elif [Expression]

Then

Statement (s)

Else

Statement (s)

Fi

Use the If to write a simple little script

Determine if a script has execute permissions, if not, give it permission to execute, and if not, create a

#!/bin/bash

File= '/root/my.sh '

If [-X $file]

Then

Echo $file

Else

Touch $file

chmod +x $file

Fi

Use case Esac to write a simple little script

According to the input parameters to judge, input R words execute a script, enter C words to create a script, enter D then delete this script, enter the other to execute this script

#!/bin/bash

Num=$1

Case $num in

X

chmod +x my.sh

;;

D

RM-RF my.sh

;;

C

Touch my.sh

;;

*)

Bash my.sh

;;

Esac

Do a little exercise, use for and if, traverse all the files in the/root directory, print out the executable file

#!/bin/bash

Path= '/root '

For file in $path/*

Do

If [-X $file-A-f $file]

Then

Echo $file

Fi

Done

Do a little exercise, use the while to write a calculation of the cumulative sum of the script, enter a number, calculate its cumulative sum.

#!/bin/bash

Num=$1

I=0

Sum=0

While [$i-le $num]

Do

sum=$ (($sum + $i))

i=$ (($i + 1))

Done

echo "$sum"

Do a little exercise and write a function that shows a file with a directory ending with. sh

#!/bin/bash

function Showsh ()

{

For file in $1/*.sh

Do

Echo $file

Done

}

Showsh $

Find–name ' *.sh '

Linux Common commands