2015/04/08 Shell Basics-1

PS: Red font is an important part, look carefully

First, Shell features

1. History view the command record, default records 1000;

[Email protected] ~]# history 1 vim/etc/hosts 2 Ifconfig 3 cd/etc/sysconfig/network-scripts/ifcfg-4 CD               /etc/sysconfig/network-scripts/ifcfg-eth0 5 ifconfig eth0 up......................../omitted [[email protected] ~]# Vim/etc/profile #可自定义history历史命令记录;

2.!! Execute the previous order;

[[email protected] ~]#!! 1 vim/etc/hosts 2 ifconfig 3 cd/etc/sysconfig/network-scripts/ifcfg-4 cd/etc/sysconfig/network-scripts/if Cfg-eth0 5 ifconfig eth0 up......................../omitted

3.! $ represents the last parameter of the previous command;

[[email protected] ~]# ls 1.txt1.txt[[email protected] ~]# ls! $ls 1.txt1.txt

4. Alias aliases;

[[email protected] ~]# alias a= "ls" #创建别名; [Email protected] ~]# A1.tar 1.txt 2.txt anaconda-ks.cfg install.log install.log.syslog[[email protected] ~]# Unalia s a #取消别名; [Email protected] ~]# a-bash:a: Command not found

5. Characters in the shell;

*: Indicates that 0 or more characters can be matched;

?: can match an arbitrary character;

#: Indicates a comment;

$: Used to mark a variable;

~: Indicates home directory;

&: Put an executable command into the background execution;

[]: Indicates the inside of the brackets select one;

6. Redirect (output), append, input, error redirect, error append;

[[email protected] ~]# ls [123].txt > Error.log

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[[email protected] ~]# cat 2.txt >> Error.log

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[email protected] ~]# Cat < 2.txt

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[Email protected] ~]# LASDASD 2> error_2.log

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[Email protected] ~]# Ndiasndias 2>> error_2.log

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7. Operation Control;

[[email protected] ~]# sleep 100            #按Crtl +z put into the background to execute; [[email protected] ~]# sleep 200            #按Crtl +z put into the background to perform;          [[email protected]  ~]# sleep 300           #按Crtl +z in the background execution; [[email protected] ~]# jobs                 #查看后台执行作业; 

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[Email protected] ~]# FG 1 #将作业调回到前台执行;

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Second, the variable

1. Custom variables;

[[email protected] ~]# a=c[[email protected] ~] # set | grep  -n ^a                  #set可以把所有变量列出来; 55:a=c[[email protected] ~]# env |  grep ^a                      #env可以列出的当前用户的所有环境变量; [[email protected] ~]# export a=aaaa                      #export引入全局变量; [[email protected] ~]# bash[[email protected] ~]# echo  $aAAAA [[email  protected] ~]# env | grep -n ^a12:a=aaaa[[email protected] ~]#  exitexit[[email protected] ~]# echo  $aAAAA 

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[Email protected] ~]# bash #取消一个自定义变量; [Email protected] ~]# unset a[[email protected] ~]# env | grep ^a

2. If you have a space in the middle of the custom variable, enclose the quotation mark;

[[email protected] ~]# a=aming linux-bash: linux: command not found[[ Email protected] ~]# a= ' Aming linux ' [[email protected] ~]# echo $ aaming linux[[email protected] ~]# b= ' echo  $a '                      # '   ' refers to the value assigned to B; [[email protected] ~]# echo  $baming  linux[[email protected] ~]# b= ' echo  $a '                      # '   ' only print out the parameters inside; [[email protected] ~]# echo  $becho   $a [[email protected] ~]# b=] Echo   $a "                     # " " refers to the value inside and prints; [[email protected] ~]# echo  $becho  aMing linux 

3. Merging variables;

[[email protected] ~]# a=2[[email protected] ~]# b=1[[email protected] ~]# c= $a ' $b ' [[email protected] ~]# echo $c 2$b[[emai L protected] ~]# c= $a "$b" [[email protected] ~]# echo $c 21[[email protected] ~]# c= $a ' $b '-bash:1: Command not found

4. System variables and user variables;

[Email protected] ~]# cat/etc/profile[[email protected] ~]# Cat/etc/bashrc[[email protected] ~]# cat. Bash_profile[[ema Il protected] ~]# cat BASHRC [[email protected] ~]# echo ' echo ' BASHRC ' >>. BASHRC [[email protected] ~]# echo ' E Cho "Profile" >>. Bash_profile[[email protected] ~]# bashbashrc[[email protected] ~]# su-bashrcprofile

Summarize:

/etc/profile and/ETC/BASHRC belong to the global configuration.

$HOME/BASHRC and $home/bash_profile belong to the user configuration.

One group takes effect for all users, and one group takes effect for the current user.

Three, Shell common commands

1. Cut split

-D: Specify delimiter;

-F: Print the first paragraph;

-C: Specifies the Intercept character;

Print the characters from the first paragraph to the three paragraph with ': ' as the delimiter;/etc/passwd; [Email protected] ~]# cut-d ': '-F 1-3/etc/passwd | Head-3root:x:0bin:x:1daemon:x:2 intercepts the first character of the/etc/passwd to the fifth character; [Email protected] ~]# cut-c 1-5/etc/passwd | Head-3root:bin:xdaemo

2. Sort sorting

-T: Specifies the delimiter;

-K: Sort the first few columns;

-N: Sort numerically (default from small to large);

-R: Reverse sort, combined with-n use;

-U: Remove duplicate rows;

With ': ' As a delimiter, the third paragraph of the/etc/passwd is sorted from small to large numbers; [Email protected] ~]# sort-t ': '-k3-n/etc/passwdroot:x:0:0:root:/root:/bin/bashbin:x:1:1:bin:/bin:/sbin/ nologindaemon:x:2:2:daemon:/sbin:/sbin/nologinadm:x:3:4:adm:/var/adm:/sbin/nologinlp:x:4:7:lp:/var/spool/lpd:/ Sbin/nologin......................../omitted to ': ' As a delimiter to sort the third character of/etc/passwd from large to small numbers; [Email protected] ~]# sort-t ': '-K 3-nr/etc/passwd user1:x:500:500::/home/user1:/bin/bashsaslauth:x:499:76: ' SASLAUTHD user ":/var/empty/saslauth:/sbin/nologindhcpd:x:177:177:dhcp server:/:/sbin/nologinnobody:x:99:99: Nobody:/:/sbin/nologinpostfix:x:89:89::/var/spool/postfix:/sbin/nologin

3. Uniq to re-

-C: Go back;

[[email protected] ~]# cat 2.txt222222333222333111222[[email protected] ~]# uniq-c 2.txt 2 222 1 333 1 222 1 333 1 111 1 222

4. WC statistics number of rows, characters, words

-L: Count rows;

-M: Statistics of characters;

-W: number of statistical words;

[[email protected] ~]# WC 2.txt7 7 2.txt[[email protected] ~]# wc-l 2.txt7 2.txt[[email protected] ~]# wc-m 2.txt28 2.txt[[email protected] ~]# wc-w 2.txt7 2.txt

5. TR Replacement Character

[[email protected] ~]# ls | Tr ' 1-9 ' A-Z ' #将数字1-9 is replaced by A-Z;

6. Split Cutting file

-B: Split by file size;

-L: divided by the number of rows;

[[email protected] ~]# du-sh 1.txt 160K 1.txt[[email protected] ~]# split-l 1.txt

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[[email protected] ~]# ls x* | Xargs-i mv {} {}.txt #将x * changed to X*.txt[[email protected] ~]# split-l 1.txt log #自定义分 The name after the cut;

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7. &&, | |,;;

&&: Execution of the following command after the execution of the preceding command;

[[email protected] ~]# ls 1.txt && cd/root1.txt[[email protected] ~]# ls aaaa.txt && cd/homels:cannot A ccess aaaa.txt:No such file or directory| |: The preceding command does not execute successfully later; [[email protected] home]# ls aaaa.txt | | Cd/root/ls:cannot access aaaa.txt:No such file or directory;: The following command executes when the preceding command is completed; [Email protected] ~]# SS; Cd/tmp

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This article is from the Chen. "Blog, be sure to keep this provenance http://chenxiaojian.blog.51cto.com/9345444/1630205

2015/04/08 Shell Basics-1