Introduction to Linux
Article Directory
One, the basic principles of linux
- 1. The '/' root is the source of the system, all files start from the root, and everything is a file.
- 2. The file can contain uppercase and lowercase letters and numbers, but the standardized file should not start with a number
- 3. Strictly case sensitive, cannot be used/as a file name
- 4. Do not do unnecessary things and do things efficiently.
Second, Bash features
2.1, shell and bash features
- 1. Type: sh, bash, zsh, tcsh, csh, ksh: view the shell command cat /etc/shell
- 2. Support command history and completion
- 3. Support pipeline, redirection, alias, support command line expansion
- 4. Support file wildcard, regular expression, support variable, shell script
- 5. ! Add keywords, only the last hop keyword command record can be executed;
- 6, echo ￥HISTSIZE can only record at most one thousand historical commands.
2.2, Quotation marks supported by bash
2.3, bash common operations
- 1, //Cursor jump
-
a.Ctrl+a/ //跳到命令行首 -
b.Ctrl+e //跳到命令行尾 -
c.Ctrl+u //删除光标至命令行首的内容 -
d.Ctrl+k //删除光标至命令行尾的内容 -
e.Ctrl+<-- //光标定位到离自己最近的一个单词前面 -
c.Ctrl+l //清屏
-
3. Command
3.1 Command format
- Command [options] [parameters]
options: there can be zero or more (short options -; long options -;)
parameters: the object of the command (there can be zero or more)
3.2, command type
Linux commands are divided into internal and external commands
- 1. Internal commands (built-in shell); provided by bash, no need to install embedded in the kernel, help+command
- 2. External command: There is an executable file with a name response under a certain path of the file system: the file path where the command exists can be found through whcich. Command ±-help
Footnote: type //Display the type of command specified by i
3.3, commonly used commands
- 1, ls: The file types viewed are
Optional file type
| - | Ordinary file |
|---|---|
| d | Directory file |
| c | Character device, charater |
| l | Link file link |
| s | Socket file |
- The type of file
- The number of hard links to the file,
- The owner of the file, (owner)
- The group to which the file belongs, (group)
- The size of the file (in bytes), (size)
- Timestamp (timestamp), the last time it was modified.
Access //access
modification // modify The content of the file has
changed //change: matadta has no data.
Command syntax *
| ls | |
|---|---|
| -l | View detailed information, the first is the type of file. |
| -d | View the catalog itself |
| -a | Do not ignore hidden files beginning with. |
| -h | Unit conversion |
| -i | Display the inode of the file |
| -r | Display in reverse order |
| -R | Recursive display |
ls -l -d ana.cfg /tmp/ks can view multiple files at the same time.
- 2. Alias alias; the syntax used alias cdnet='cd /etc/syscpnfig' directly defines the alias to enter the directory.
- 3. cd change directory: change directory
usage -
绝对路径和相对路径。 -
cd 回到主目录，cd 回到上次目录，cd~回到用户主目录。 -
cd - 来回切换，类似回看，直接与上次路径进行切换。 - 4. pwd: current path, display the current location
- 5. mkdir new folder, new directory
- usage
| mkdir | description |
|---|---|
| -p (praent parent) | Create subfolders after creating the parent folder. |
| -v (verbose verbose) | Echo the process of creating a folder |
Use Cases;
-
6. rmdir delete directory: only one non-empty directory can be deleted
-
7, tree: View the directory tree and display the contents of the current directory in a tree-like structure.
example:
-
8, touch: create a file, divided into two ways: "made out of nothing", "leave the old and welcome the new-reset the time of the file"
-
9, stat: view the status of the file, view the file's access time, modification time, change (file size) change (content change)
such as
-
10, rm, remove move delete, delete file directory
Optional parameter
-r: delete recursively. This option
-f must be used when deleting a directory ; it is forced to delete without asking. :
Only use -f to delete files, and -r to delete directories
- 11. cp: copy
Optional parameter
-r: copy directory
-f; forced copy. :
-a; archive copy, often used for backup.
-p; retain the original permissions when copying. - 12. mv, move move files, (rename locally), cut files (the target is cut at the remote end)
- 13, cat: View file content ---- link multiple files, view multiple files, merge content, generate multi-line text.
- 14. echo'hello' >abc write to the file echo echoes the written content,> one is to overwrite, >> two is to append. '
cat >abc <<EOF When writing the file to abc, <<EOF will end writing when detecting this EOF. And >> append is the same, when EOF is detected, it will end writing. - 15, tac: Reinstall: link me to see and flashback print content to load to content.
- 16, more: //View text content in full screen, only from front to back
- 17, less: view the text content in full screen, you can view from front to back, or from back to front, use b to look forward, and space to look back
- 18. head View the contents of the file from the head, the first 10 lines are viewed by default, and the number of lines can be specified by -n, head -10 abc to view the file
- 19, tail looks at the content of the file from the end, the last 10 lines are viewed by default, you can also specify the number of lines with -n, tail -10 abc to view the last 10 lines of the file
- 20, wc: text statistics, word count
Usage: -w counts words, -f counts lines, -c counts characters
such as
- 21, du statistics file size, -sh summary hunman summary information, s view directory, h view with unit.
- 22, df: Report file system disk space usage, -h displays in a human-friendly way, -i displays inode information
Such as:
- 23, hostname: view and temporarily set the host name, change the host name, restart will resume.
- 24, hostnamectl: Permanently set the host name, command use method hostnamectl set-hostname host name, and then use bash to refresh the host name
- 24, clear, please screen , clear all the contents of the terminal, shortcut key Ctrl + l
- 25, whoami displays the currently logged-in user
- 26, who displays all currently logged-in account information
- 27, w, show all logged-in accounts and show what they are working on
- 28, which View the location of the command.
[root@Eryuege admin]# which cd
/usr/bin/cd
- 29, date //Display the current time, or set the time How to
use
| Options | description |
|---|---|
| -s | Set the time in characters, such as date -s '2020-10-17 10:30:00' |
| %Y | years |
| %m | month |
| %d | date |
| %H | Time |
| %M | Minute |
| %S | second |
- 30, cal perpetual calendar
- 31. ldd checks the files that the command depends on. Remember not to move the files that the command depends on without taking a snapshot. The bloggers have encountered bloody lessons! ! !
- 32, tar: file compression tool
Compressed file classification
| File extension | Tools used |
|---|---|
| … Tar.gz | tar |
| .tar.bz2 | tar |
| .tar.xz | tar |
| .zip | zip universal cross-platform. |
The compression ratio will become smaller and smaller.
How to use tar
| Options | Features |
|---|---|
| -c | Create archive |
| -with | Compressed into gz format |
| -j | Compressed into bz2 format |
| -J | Compressed into zx format |
| –V | Show details |
| -t | View the contents of the compressed package without decompression |
| -f | 指定要压缩或解压缩的文件 |
| -x | 解压缩 |
| 组合键使用 | |
| -zcf | 创建一个gz格式的压缩文件 |
| -jcf | 出啊关键一个bz2格式的压缩文件 |
| -xvf | 解压指定文件，并查看过程 |
| -xf | 解压指定文件 |
| -C | z指定解压的目录 |
| zip压缩文件 | zip 1.zip 1， 2 4 5 6 7 7可以将多个文件压缩进一个压缩文件 |
| unzip | 解压缩文件 |
安装依赖文件的方法
3.3，文本处理之文本三剑客awk-sed-grep！！！
- 1,cut :截取文本的内容，-d指定字段的分割符，默认是空格，-f指定要显示的字段。
- 2，awk：取出指定列的内容；awk -F分割符 ’NR==行数{print $需要的列}‘ filename
分割符不指定默认是空格， 取 正 数 值 的 内 容 ， N R 指 定 行 数 ， N F 指 定 最 后 一 列 ， 可 以 通 过 取正数值的内容，NR指定行数，NF指定最后一列，可以通过 取正数值的内容，NR指定行数，NF指定最后一列，可以通过（NF-2）查看倒数第二列的内容
- 3，sed：处理行的内容；sed [option] ’需要处理的动作‘ filename
-n 关闭默认的打印动作。只打印需要处理的动作。
如“
[root@Eryuege admin]# sed -n ‘1s/root/123/p’ passwd
123❌0:0:root:/root:/bin/bash
sed ’1s/123/abc/g‘ abc 处理第一行的123替换位abc并打印。
| 参数 | 描述 |
|---|---|
| 1 | 表示第一行 |
| s | 表示修改替换 |
| c | 表示改变 |
| a | 表示追加内容 |
| g | 表示全部，如果1表示第一个匹配 |
| D | 删除 |
| p | 打印 |
![[root@Eryuege admin]# du -sh passwd 4.0K passwd](https://img-blog.csdnimg.cn/20201017155040116.png#pic_center){kind=link}
- 4，gerp 过滤文本的内容
- 4.1，grep egrep fgrep
：根据模式搜索文本，并将符合模式的文本显示出来。
：使用基本正则表达式定义的模式来过滤文本的命令。
（Pattern 模式） 文本字符和正则表达式的元字符组合而成的匹配条件。
选项参数
| 选项 | 描述 |
|---|---|
| -i | 忽略大小写 |
| - - color | 匹配带的内容高亮显示 |
| -v | 显示没有被模式匹配到的行 |
| -o | 只显示被模式匹配到的字符串 |
| -E | 使用扩散正则表达式，grep -E相当于使用egrep |
| -q | 静默模式，不输出任何信息 |
| -A（after后） 1 | 被模式匹配到的内容以及其后面一行的内容都显示出来 |
| -B （before前）1 | 被模式匹配到的内容以及其前面一行的内容都显示出来 |
| -C （前后）1 | 被模式匹配到的内容以及其前后的行各显示1行。 |
示例:
root@Eryuege ~]# grep -A 2 ‘hell’ ac
hell world
cat
han de
[root@Eryuege ~]# grep -B 2 ‘hell’ ac
1231
heloo
hell world
[root@Eryuege ~]#
- 4.2,，fgrep 不支持正则表达式，执行行速度快
实例：[root@Eryuege ~]# cat ac |grep ‘world’
hell world
- 5，sort：默认神曲排序，不是桉数值大小排序的.
用法
| sot选项 | 描述 |
|---|---|
| -n | 根据数值大小进行排序 |
| -r | 逆序排序 |
| -t | 字段分隔符 |
| -k | 以那个字段为关键字进行排序 |
| -u | 去重，排序后相同的行至显示一次 |
| -f | 排序是忽略字符大小写 |
| uniq选项 | 描述 |
| -c | 显示文件中行重复的次数 |
| -d | 只显示重复的行 |
| -u | 只显示未重复的行 |
通过-E多个内容同时查找|通过正则表达式进行查找
[root@Eryuege ~]# grep -E ‘123|ha’ ac
1231
han de
4，获取帮助：
- 1，通过man命令查看手册。
- 2，通过–help查看简要帮助说明
- 3，通过pinfo查看详细手册说明。
//内部命令
help COMMAND
//外部命令
COMMAND --help
//在线文档
info COMMAND
//命令手册 manual
man COMMAND
//文档
/usr/share/doc
whatis COMMAND //用于查看COMMAND出现在man的哪一章节中。
//man是分章节的，以下是每一章节的内容介绍：
1 用户命令（/bin,/usr/bin,/usr/local/bin）；
2 系统调用；
3 库调用；
4 特殊文件（设备文件）；
5 文件格式（配置文件 的语法）；
6 游戏；
7 杂项（Miscellaneous）；
8 管理命令（/sbin,/usr/sbin,/usr/local/sbin）
//man manual note:
[] //optional
<> //required
... //can appear multiple times
| //choose one more
{} //group
name //command name and function brief description
SYNOPSIS //usage Description, including the available options
DESCRIPTION //Detailed description of the command function, possibly including the meaning of each option
OPTIONS //Description of the meaning of each option
FILES //Configuration files related to this command
BUGS //Report bug
EXAMPLES //Examples
SEE ALSO //Also reference
//man flips the screen, flips
one screen backward//SPACE flips one screen
forward //b
flips one line backward//enter
flips one line forward//k
//Find
/KEYWORD //backward
? KEYWORD //forward
n //next
N //previous
q //exit