Shell Introduction, Command history, command completion and aliases, wildcard characters, input and output redirection

Shell Introduction

The shell is a command interpreter that provides interaction between the user and the machine, supports specific grammars, such as logical judgments, loops, and each user can have their own specific shell

CentOS7 default shell is bash (Bourne Agin Shell)

and zsh, Ksh and so on.

Command history

View history Commands

[email protected] ~]# cat. bash_history

Modify History Bar Number:

Vi/etc/profile

histsize=1000

To modify the format of viewing history:

New in/etc/profile:

histtimeformat= "%y/%m/%d%h:%m:%s"

Source/etc/profile

841 2017/10/20 06:01:05 Vi. bash_history

842 2017/10/20 06:02:03 Vi/etc/profile

843 2017/10/20 06:03:23 Source/etc/profile

844 2017/10/20 06:03:27 History

Add Permission control:

[Email protected] ~]# chattr +a. bash_history

[Email protected] ~]# > Bash_history

-bash:. Bash_history:operation not permitted

!! : Indicates the execution of the previous command

! 844: Represents a command that executes 844 rows

!his: Represents the command that executes the start of his, which is the last executed

Command completion and aliases

1.Tab Completion

2, Parameter Complete installation bash-completion

Alias aliases

[email protected] ~]# alias wo= ' Ls/root ' #临时有效

[email protected] ~]# wo

2.txt 2.txt.bz2 anaconda-ks.cfg

Permanently valid:

[Email protected] ~]# Vi. BASHRC

#. BASHRC

# User specific aliases and functions

Alias wo= ' Ls/root '

Wildcard characters

1, [[email protected] ~]# ls *.txt

2.txt David.txt

2.

[email protected] ~]# ls?. Txt

2.txt

[email protected] ~]# ls??. Txt

23.txt

[[email protected] ~]# ls [0-9].txt

2.txt

[[email protected] ~]# ls [0-9][0-9].txt

23.txt

[[email protected] ~]# ls {2,23}.txt

23.txt 2.txt

Redirect:

Cat 1.txt >2.txt

Cat 1.txt >> 2.txt

[[email protected] ~]# cat 23.txt >> 2.txt &>/dev/null

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Shell Introduction, Command history, command completion and aliases, wildcard characters, input and output redirection