2018.4.21 Five week fourth class (Shell special symbol, cut intercept and other commands)

Shell Special Symbol _cut command

概念：cut命令用来截取某一个字段格式：cut -d ‘分割字符‘ [-cf] n,这里的n是数字，该命令选项有如下几个：- d 后面跟分割字符，分割字符要用单引号括起来- c 后面接的是第几个字符- f 后面接的是第几个区块

The Cut command uses the following

[Email protected] do]# cat/etc/passwd |head-2
Root:x:0:0:root:/root:/bin/bash
Bin:x:1:1:bin:/bin:/sbin/nologin
[[email protected] do]# cat/etc/passwd |head-2 |cut-d ': '-F 1
Root
Bin
[Email protected] do]# cat/etc/passwd |head-2 |cut-d ': '-f
Root:x
Bin:x
[[email protected] do]# cat/etc/passwd |head-2 |cut-d ': '-f 1-3
root:x:0
Bin:x:1

Cat passwd This file, head only look at the first two lines, cut-d intercept the split symbol as ":",-F 1 to intercept the first paragraph, the previous two paragraphs, 1-3 represents the first three paragraphs.

Sort sorts _WC count rows _uniq Delete duplicate rows Sort command Introduction

sort命令用于排序格式：sort [-t 分隔符] [-kn1,n2] [-nru]这里-n1和n2指的是数字，其他选项如下：-t 后面跟分割字符，作用跟cut -d选项一样，截取符号是什么；-n 表示使用纯数字排序，字母及特殊符号表示为0；-r 表示反向排序；-u 表示除去重复；-kn1,n2 表示由n1区间排序到n2区间，可以只写-kn1，即对n1字段排序。

• Example: If sort does not have any options, he is the default ascending output, and we assume that there is a difference between the five elements before looking at the passwd configuration file.

  [Email protected]/]# head-n5/etc/passwd |sort
  #查看passwd前五行, output to sort (sort) execution, sorted by default ascending order.
  Adm:x:3:4:adm:/var/adm:/sbin/nologin
  Bin:x:1:1:bin:/bin:/sbin/nologin
  Daemon:x:2:2:daemon:/sbin:/sbin/nologin
  Lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
  Root:x:0:0:root:/root:/bin/bash

Example 2: Write the first 10 lines of the passwd configuration file to 3.txt, and then add a few special symbol numbers to sort.

, we sort by sorts, sort by numbers-n
[[email protected] do]# sort-n 3.txt #-n indicates a positive sequence, and special symbols and letters are represented as 0

As shown in the first diagram, we-R gives the reverse sort look
[[email protected] do]# sort-r 3.txt #-r for reverse order

WC command Introduction, used to count

概念：wc命令用于统计文档的行数，字符数或词数。选项：-l 统计行数-m 统计字符数-w 统计词数，以空格作为区分

• Here's how:

  [Email protected] do]# wc/etc/passwd #查看这个文档的行数, number of words and word count
  846/etc/passwd
  [Email protected] do]# wc-l/etc/passwd #统计行数
  19/etc/passwd
  [Email protected] do]# wc-m/etc/passwd #统计字数
  846/etc/passwd
  [Email protected] do]# wc-w/etc/passwd #统计行数
  27/etc/passwd

Command Uniq to delete duplicate rows

概念：uniq命令用来删除重复的行，改名了只有-c选项比较常用；它表示统计重复的行数，并把行数写在前面。

• Write a file with the following example:

  [email protected] do]# Touch 4.txt #创建一个文本
  [Email protected] do]# VI 4.txt #编辑内容
  111
  222
  333
  111

• Before using Uniq, it must be dedicated to file sorting, otherwise, the example is as follows:

  [email protected] do]# cat 4.txt #查看里面的内容
  111
  222
  333
  111
  [Email protected] do]# uniq 4.txt #测试一下看看不排序管用么, no matter
  111
  222
  333
  111
  [[email protected] do]# sort 4.txt |uniq #sort排序4. txt file, then output to uniq delete duplicate rows
  111
  222
  333
  [Email protected] do]# sort 4.txt |uniq-c #统计重复的有行, how many
  2 111
  1 222
  1 333

Command tee, redirect and display content

tee命令后面跟文件名，起作用类似于重定向>，但它比重定向多一个功能；把echo输出的结果，通过管道符“|” tee输出给后面的文件并在屏幕上显示。

• Here's how:

  [email protected] do]# Touch 1.txt #创建一个文本
  [Email protected] do]# echo "1321asd123" | Tee 1.txt #把echo的内容通过管道符号, output to the tee command, to a 1.txt file, and display the results on the screen.
  1321asd123

command TR, for replacing characters

tr命令用于替换字符，常用来处理文档中出现的特殊符号；如DOS文档中出现的符号^M，该命令常用的选项如下：-d 表示删除某个字符，后面跟要删除的字符；-s 表示删除重复的字符。

• Suppose a small l of a file is changed to a large L

  [[email protected] do]# echo "Linux" > 1.txt
  [email protected] do]# cat 1.txt
  Linux
  [[email protected] do]# echo "Linux" | TR ' [l] ' [l] ' #把前面的小l, changed to L
  Linux

Command split, cut the document

split命令用于切割文档，常用的选项为-b和-l-b 表示依据大小来分割文档，默认单位为byte（字节）-l 表示依据行数来分割文档

• First search out a content, and all the content of cat out, chasing the heavier directed to a file to go

  [Email protected]/]# find/etc/-type f-name "*conf"-exec Cat {} >>/tmp/do/1.txt \;
  #find search for the file name under/etc/Ask Conf the end of the file, cat {} The contents of the view, appended to the 1.txt file.
  [Email protected]/]# Du-sh/tmp/do/1.txt #查看这个文件的大小
  212k/tmp/do/1.txt

• Example 1: This file has 212K, we give him a cut specify a size of 100K to try, the example is as follows:

  
  #这里,-B is specified with 100K, and no units are displayed in bytes by default.

• Example 2: Specify the file that begins with the target file name 123.

  
  #x开头的文件, which is the result of example 1, does not need to look at him, look at the 123-beginning file to form a contrast.

Shell Special Symbols

  key chapters, which will often be used later in the "# # # # # Special symbol $-symbol $ can be used as the identifier before the variable, and can be! Used together, examples are as follows: >[[email protected] do]# [[email protected] do]# ls/tmp/do/123aa 1.txt 2.txt 3.txt 4.txt A. TXT XAA xab xac[[email protected] do]#!lsls/tmp/do/123aa 1.txt 2.txt 3.txt 4.txt a.txt xaa xab xac!$ = Previous Bar The last variable in the command. # # # Special symbols;-If you want to run two or more commands in a row, you need to add a symbol between the commands: >[[email protected] dior1]# mkdir 123; Touch 1.txt; Touch 2.txt; ls123 1.txt 2.txt above meaning, created a directory, and created 2 files, and the last LS View execution # # # special symbol ~-symbol ~ Indicates the user's home directory, the root user's home directory is/root, the ordinary user is/home/username#### Special symbol &-If you want to put a command in the background, you need to add a symbol &, which is usually used for long command times, can be used in sleep (sleep), the example is as follows: >[[email protected] ~]# sleep  & [1] 40966[[email protected] ~]# jobs [1]+ run in Sleep &#### redirect symbols >, >>, 2>, 2>>, &> usage  

Concept:>, >> they represent the meaning of substitution (>) and append (>>) respectively;
When we run a command error, the error message will be output to the current screen;
If you want to redirect to a text, you need to use the redirect symbol 2> or 2>>;
They represent error redirection and error append redirection, respectively.
&> indicate errors and correct redirection input into a file

#### 中括号[] - 中括号内为字符组合，代表字符组合中的任意一个。（上一章节有提到）#### 特殊符号 &&和||- 使用||时，表示或者，意思是说 如果两条命令用||分割的话，第一条执行成功后，第二条就不会执行，假如第一条命令是错误的话，执行失败就会执行第二条。> 示例1，假设两个命令都是正确的> [[email protected] do]# ls 1.txt || wc -l 2.txt 1.txt>示例2： 假设第一条命令是错误的，而第二条命令是正确的，就会执行第二条[[email protected] do]# ls 111111.txt || wc -l 2.txt  #在这里 根本就没有一串1的txt文件ls: 无法访问111111.txt: 没有那个文件或目录0 2.txt- 使用&& 表示前面的命令执行成功以后，才会执行后面的命令，如果前面命令执行不成功，后面的命令就不会执行。用&&分割，用来判断的。>示例1，两条命令都是正确的情况下 >[[email protected] do]# ls 1.txt && wc -l 2.txt #ok，在这里两条命令都生效1.txt0 2.txt>示例2，假如第一条命令不成功，后面的命令就不会执行。>[[email protected] do]# ls 111.txt && wc -l 2.txt ls: 无法访问111.txt: 没有那个文件或目录# 普通特殊符号介绍

• Any of any characters
  ? Any one character
  #注释字符
  \ de-Semantic characters
  | Pipe character

2018.4.21 Five week fourth class (Shell special symbol, cut intercept and other commands)