Shell script Implementation empties log

#!bin/bash

Log_dir=/var/log

Root_uid=0

if[' $UID '-ne ' $ROOT _uid ']

Then

Echo ' must is root to run this srcripts '

Exit 1

Fi

CD $Log_dir | | {

echo "Cannot change Necessarydirectroy" >&2

Exit 1

}

Cat/dev/null >messages&&

Echo ' log is cleaned up. '

Exit 0 #返回0 Indicates success, 1 indicates failure

650) this.width=650; "Src=" https://s3.51cto.com/wyfs02/M02/9C/62/wKioL1lvypHAiZmxAAEGHHfBKsk549.png-wh_500x0-wm_ 3-wmp_4-s_2820742897.png "title=" 655.png "alt=" Wkiol1lvyphaizmxaaeghhfbksk549.png-wh_50 "/>

Types of shells

650) this.width=650; "Src=" https://s2.51cto.com/wyfs02/M01/9C/62/wKioL1lv1lDwddflAADxcly1ozU203.png-wh_500x0-wm_ 3-wmp_4-s_1394413097.png "title=" 1122121.png "alt=" Wkiol1lv1ldwddflaadxcly1ozu203.png-wh_50 "/>

Default shell for common Linux systems

650) this.width=650; "Src=" https://s4.51cto.com/wyfs02/M02/9C/62/wKiom1lv14Cw3iv0AAFFcST_DJI591.png-wh_500x0-wm_ 3-wmp_4-s_1681327574.png "title=" 22222.png "alt=" Wkiom1lv14cw3iv0aaffcst_dji591.png-wh_50 "/>

View Shell;echo$shell;bash used by Linux--Vsion

Shell Execution Method:

650) this.width=650; "Src=" https://s5.51cto.com/wyfs02/M02/9C/62/wKiom1lv2PnT5vMCAAIWiNsqvzI706.png-wh_500x0-wm_ 3-wmp_4-s_133048985.png "title=" 1111111111111111.png "alt=" Wkiom1lv2pnt5vmcaaiwinsqvzi706.png-wh_50 "/>

Shell Environment variables:

650) this.width=650; "Src=" https://s4.51cto.com/wyfs02/M00/9C/62/wKiom1lv3DWya3EnAAricAnQwJY523.png-wh_500x0-wm_ 3-wmp_4-s_170482539.png "title=" 4444.png "alt=" Wkiom1lv3dwya3enaaricanqwjy523.png-wh_50 "/>

Export lang=en

Set Environment variables (global), environment variables must be uppercase ;

"The single quotation mark is what you see is what you receive;

" '" double quotation marks: The variables and commands in the quotation marks will be parsed out, it is recommended to use

No quotation marks: consecutive can not double shadow number

Awk has nothing to do with the good shell of the upper;

NFS is the abbreviation of the network file system;

Create 10 of files in bulk with the shell

#！ /bin/bash

Dir =/test

[!-D $ dit]&&mkdir-p $dir

For file in ' Seq10 '

Do touch/test/test-$file. html

Done

Cond..

Shell script Implementation empties log