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Linux Basics Series 1

步履不停
步履不停Original
2019-06-19 15:44:302629browse

Linux Basics Series 1

Basic concepts

  1. Linux system has file management like Windows, and the file path is divided into absolute path and relative path. The absolute path starts with /, such as /usr/local, while the relative path does not start with /, such as ../, which is the upper level of the current directory.

  2. In the Linux system, different users have different home directories (that is, the initial location of Linux when different users log in). If you log in as the root account, the home directory is /root/. If you log in as the ordinary user xxx, the system's default home directory is /home/xxx/. Of course, you can also specify the ordinary user's home directory as another directory. Later, The article will be added.

Commonly used commands

1. pwd, check the absolute path of the current directory, the display starts from /

2. ls, check the current path File or folder

ls / 只显示该目录下的文件或文件夹的名称
ls -l / 显示该目录下的文件或文件夹的明细信息,ls -l ==>ll,更多用ll代替
例如:
[hadoop@hadoop01 ~]$ ls -l /home
total 0
drwx------(权限) 2 hadoop(用户) hadoop(用户组) 79 Jun  3 19:31(时间) hadoop(文件或文件夹名称)
ll -h 查看文件大小,只能看文件不能看文件夹,如果想看文件夹大小,请使用du -sh 文件或文件夹名
ll -rt 给文件或文件夹以时间排序,可以找出最新的文件或文件夹

3. cd, switch directory

cd -    回到上一次目录  
cd ../  回退上一层目录(相对路径)
cd ../../ 回退2个目录(相对路径)
三种回到家目录方法:cd+回车,cd ~,cd /用户的家目录的绝对路径

4. mkdir, create folder

mkdir xxx 只能创建1个
mkdir -p xxx/1/2 级联创建文件夹
mkdir 4 5 6 并行创建4 5 6 文件夹

5. vi/touch, create file

touch 文件名
vi 文件名 
1.命令行模式 i进入编辑模式
2.esc 回退到命令行模式
3.shift+:尾行模式  wq保存退出

6, cp, copy files/folders

cp xxx.log xxx/
cp -r xx xx/     文件夹拷贝 需要-r参数

7, mv, move or rename files/folders

mv test.log test                移动文件到新的地方 名称不变
mv test1.log  test/test123.log 移动文件到新的地方 名称变   
mv test1 test  移动文件夹

8, cat/more/less, View file content

cat  文件内容一下子全部显示 适用字节内容较少
     查看日志的内容ERROR 定位错误
	假如文件超大 10m   发送给window电脑,通过editplus 全局搜索
	假如文件假如100m+(grep -C 是指搜索"ERROR"前后10行)
	cat install.log | grep -C 10 "ERROR"
	假如 ERROR筛选的结果 特多(> 重定向覆盖输出到文件,>> 追加)
	cat install.log | grep -C 10 "ERROR" > error.log

more 文件内容一页一页的往下翻 按空格键往下 
	回退不了 按q退出   适用字节内容稍多的 
less 文件内容 一行行 按箭头上下  按q退出

9, tail, real-time view

实际工作中,对于日志总会面临日志过大的问题,一般使用切割法。
到达某个数值,mv xxx.log xxx.log1,然后再touch xxx.log。
推荐使用 tail -F xxx.log,-F=-f+retry,-f 不够强大,文件只要被移走,就算新的一模一样,也不会实时监控
[root@hadoop001 ~]# tail -F xxx.log 
123
4
tail: `xxx.log' has become inaccessible: No such file or directory
tail: `xxx.log' has appeared;  following end of new file
5
但是如果你要看以倒数50行开始的日志,只能是tail -50f xxx.log

10, help, command help

命令 --help
例如:
[root@hadoop001 ~]# ls --help
Usage: ls [OPTION]... [FILE]...
[]代表可以省略

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