Linux_note Special symbols in the shell

* Represents 0 or more arbitrary characters

? Represents only one arbitrary character

# comment Symbols

\ de-signifier symbol

[[email protected] ~]# ls #1. txt #将后面内容注释 only run LS

111 1.tar 3.txt Install.log yasuo.zip

111.tar 1.txt anaconda-ks.cfg Install.log.syslog

123.txt 2.txt a.txt Yasuo

[[email protected] ~]# ls \ #1. txt \ de-ideographic character to remove the original meaning

LS: Unable to access #1.txt: There is no file or directory at this time #1.txt as the file name

[email protected] ~]# touch \ #1. txt|ls

111 123.txt #1. txt 2.txt anaconda-ks.cfg install.log Yasuo

111.tar 1.tar 1.txt 3.txt a.txt install.log.syslog yasuo.zip

| Pipe character

The $ variable prefix that gets or uses the variable when it is preceded by the $

!$ represents the last variable in the previous command

[Email protected] ~]# echo $PATH

/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/tmp/:/data/bin/:/root/bin

[Email protected] ~]#!$

$PATH

-bash:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/tmp/:/data/bin/:/root/bin:

No file or directory

; Used in the middle of two commands (two commands written on one line)

[[email protected] ~]# ls 1.txt; LS 1.tar

1.txt

1.tar

~ User Home Directory

[[email protected] ~]# ls ~

111 123.txt #1. txt 2.txt anaconda-ks.cfg install.log Yasuo

111.tar 1.tar 1.txt 3.txt a.txt install.log.syslog yasuo.zip

& put commands in the background (add & after a command)

[Email protected] ~]# & Sleep

[1] 1647

[[email protected] ~]# jobs

[1]+ Running Sleep &

[[email protected] ~]# jobs

[1]+ done Sleep 10

REDIRECT symbol: >,>>,2<,2<<,<

#echo "123" >1.txt > overwrite the contents of the original file 1.txt

[Email protected] ~]# echo "123" >1.txt

[email protected] ~]# cat 1.txt

123

If you do not want to overwrite with append redirect >>

[Email protected] ~]# echo "456" >>1.txt

[Email protected] ~]# echo "789" >>1.txt

[email protected] ~]# cat 1.txt

123

55W

789

Reverse redirect < Throw a file content to a command

such as: [[email protected] ~]# Wc-l < 1.txt

3

Error redirection:2>,2>>

[[email protected] ~]# ls 11111

LS: unreachable 11111: No file or directory

[[email protected] ~]# ls 11111 > 1.txt will also overwrite the original file content

LS: unreachable 11111: No file or directory [[email protected] ~]# ls 11111 2> 1.txt

[email protected] ~]# cat 1.txt

LS: unreachable 11111: No file or directory

Do not overwrite the original file content:2>>

[[email protected] ~]# ls 11111 2>> 1.txt

[email protected] ~]# cat 1.txt

LS: unreachable 11111: No file or directory

LS: unreachable 11111: No file or directory

[] A character combination in parentheses that represents any of the characters

[[email protected] ~]# ls [123].txt

1.txt 2.txt 3.txt

[[email protected] ~]# ls [1-9a-za-z].txt

1.txt 2.txt 3.txt A.txt

Linux_note Special symbols in the shell