Command Shell to learn

For i in a B C

Do

Echo $i

Done

!ser Historical complements

> Correct information output file

>> correct information output file, append

2> error message output file

2>> error message output file append

&>> all outputs

free-m | Grep-i Mem | awk ' {print $4,$3} '

PWD current Directory

ID Current Login User

Add a user to the group

Gpasswd-a User1 Root

CHOMD a+w (All) u+w (user) g+w (group) o+w (other users)

Specify user chmod with Setfacl/getfacl

Specify another user's permissions on a command

Visudo

For i in ' ls '

Do

echo "---> $i"

Done

Name= "Fasdfsad" (no spaces in the middle)

$ (variable)

Echo $name

Read-p "fasdfsadfs->" name

Echo $name

---------

Case $ in start)

echo "Start"

;;

Stop

echo "Stop"

;;

Esac

echo $ (($1+$2))

Expr $ + $ (must have a space)

$ #个数 $* All contents $? Last command status $ A program name

For I in $*

Do

Echo $i

Done

if [[$ = = 0]]; Then

echo "OK"

Else

echo "No"

Fi

num = ' Expr 2 + 3 + 4 '

num = ' Expr 4 \* 2 '

Echo-e recognize \ n characters-n No line break

Echo-e "\033[32;40maaaaa\033[0m"

033[foreground color, background color m

033[0m Restore System Colors

[-d/root/aaa.txt] && echo "yes"

Command shell Learning