2016-2-4 Linux Basic Learning 10

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Computer 5 major devices: Arithmetic, controller (CPU), Memory (RAM), input device, output device

Programs: Directives and data
Address bus: Memory addressing
Data bus: Transferring data
Control Bus: Control instructions
Register: CPU Ephemeral memory

I/O devices:
Input device:
Output device:
System settings
Default output device: Standard output, STDOUT, 1
Default input device: standard input, Stfin, 0
Standard error Output: STDERR, 2

Standard output: Keyboard
Standard output and Error output: Display

I. I/O redirection
Output Redirection (>): Overwrite output
(>>): Append output 650) this.width=650; "Src=" http://s5.51cto.com/wyfs02/M00/7A/C2/ Wkiom1azvdpd5lp2aaa2zbqxzn8077.gif "style=" width:550px;height:423px;float:left; "title=" Output redirect 1.gif "height=" 423 " Hspace= "0" border= "0" vspace= "0" width= "550" alt= "Wkiom1azvdpd5lp2aaa2zbqxzn8077.gif"/>650) this.width=650; "Src= "Http://s5.51cto.com/wyfs02/M01/7A/C2/wKiom1azVDTCqG-CAABICQlsbqw687.gif" style= "WIDTH:550PX;HEIGHT:249PX;" title= "Output redirect 2.gif" height= "249" hspace= "0" border= "0" vspace= "0" width= "550" alt= "wkiom1azvdtcqg-caabicqlsbqw687.gif "/>

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SET-C: Disable overwrite redirection for already existing files
Set+c: Allow overwrite redirection for already existing files
Force overwrite output, use >|

2>: Redirect Error output
2>>: Append method

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&>: Redirect standard output or error output to the same file
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Ii. Input Redirection (<): Enter into the specified file (Show/execute)
(<<): Here document generates documents here

third, Pipeline : The output of the previous command, as the input of the latter command
Command 1 | command 2 | Command 3 | ...
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Tee: Read data from standard input, output to a copy of the screen, and save to a file

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4-3 Practice
1, Count files in/usr/bin directory
    # ls/usr/bin | wc-l
2, remove shell for all users on the current system, request, Each shell is displayed only once and is displayed sequentially, counting the number of occurrences of each shell
    # cut-d:-f7/etc/passwd | sort-n | uniq-c
3, thinking: How to display the/V What is the content type of each file in the Ar/log directory?
     France:
    # cd var/log
    # file ' ls/var/log '
      II:
    # file/var/log/*
4, remove the 6th line of the/etc/inittab file
    # head-6/ Etc/inittab | TAIL-1
5, take out the user name and shell of the 9th user in the/etc/passwd file, display it to the screen and save it to the/tmp/users file
    # tail-9/etc/ passwd | head-1 | Cut-d:-F 1,3 | Tee/tmp/users
6, display all files starting with PA in/etc directory, and count the number of them
    # ls-d/etc/pa* | wc-l
7, text Editor not applicable, alias cls= The clear line is added to the current user's. bashrc file
    # echo "Alias Cls=clear" >> ~/.BASHRC

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2016-2-4 Linux Basic Learning 10