[TOC]

A, DAY1

1. What is the shell

A shell is a command interpreter, providing interaction between the user and the machine (shell script is a manifestation of the shell)
Support specific syntax, such as logic, loop (if, for, while)
Each user can have their own specific shell
- root:x:0:0:root:/root:/bin/bash
CentOS7 default shell is bash (Bourne Agin Shell)
There zsh, ksh, etc.

2. Command History

history command
.bash_history Record store command files, if non-terminal exit, logout normal exit, command incomplete documentation.
Maximum 1000, 1000 by default, can be modified
Variable HISTSIZE, see echo $HISTSIZEif the display of more than 1000, because the command is temporarily stored in memory, not written into the file, history-cbut does not clear the memory may clear the records .bash_historyin the record
/etc/profileModify, after the changes take effect immediately to re-enter the terminal or execution source /etc/profile
HISTTIMEFORMAT="%Y/%m/%d %H:%M:%S " Increasing this variable execution time, the command corresponding to the record can be, for example: 1005 2019/11/12 10:29:47 w
Stored permanently chattr +a ~/.bash_historyeven over 1000 did not have permission to delete
On a command !!
! Nn is a number, execute the command history recorded in the corresponding number of
!word

3. Command completion and aliases

tab key, knock, knock twice
centos7 support parameter completion, the installation yum install -y bash-completionwill require a reboot to take effectsystemctl restart network
alias alias to command a name again alias restartnet="systemctl restart network"to cancel alias:unalias restartnet
Each user has its own configuration file aliases ~/.bashrc
ls /etc/profile.d/

alias into custom~/.bashrc

# .bashrc

# User specific aliases and functions

alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'
alias restartnet="systemctl restart network"
# Source global definitions
if [ -f /etc/bashrc ]; then
        . /etc/bashrc
fi

4. wildcard, input and output redirection

ls *.txt
ls ?.txt
ls [0-9].txt
ls {1,2}.txt
cat 1.txt >2.txt
cat 1.txt >> 2.txt
ls aaa.txt 2> err // 2> represents the error redirection
ls aaa.txt 2 >> err // 2 >> indicates an error appending redirection
&> Combination of right and wrong redirection
wc -l < 1.txt
command >1.txt 2>&1

Two, DAY2

The job control pipe, and

cat 1.txt |wc -l ; cat 1.txt |grep 'aaa'
The results back to the front of the command
ctrl z suspend a task
jobs View background tasks
bg [id] transferred back to the task
fg [id] the task to the foreground.
Plus direct throw after the command & background sleep 100 &

6.shell variable

PATH, HOME, PWD, LOGNAME often wind of some of the system variables
env command can be used to view the system variables, the system is generally capitalized variable name, a variable value may be a value, or a string
set command a lot more variables, including variables and user-defined
Custom Variables a = 1
Variable name rule: letters, numbers underlined, the first number can not be a1 = 4 a_1 = 4 but not 1a = 4

Variable values will need enclosed in single quotes special symbols

a='a b c' Inside the spaces use single quotes

[root@mydb1 ~]# a="a$bc"
[root@mydb1 ~]# echo $a
a
[root@mydb1 ~]# a='a$bc'
[root@mydb1 ~]# echo $a
a$bc
在取值时，单引号和双引号结果不一样，所以在取值时要用单引号

Use double quotes accumulation variable, the variable accumulation

[root@mydb1 ~]# a=1
[root@mydb1 ~]# b=2
[root@mydb1 ~]# echo $a$b
12
[root@mydb1 ~]# a='a$bc'
[root@mydb1 ~]# echo $a$b
a$bc2
[root@mydb1 ~]# c="a$bc"
[root@mydb1 ~]# echo $c
a
[root@mydb1 ~]# c="a$b"c
[root@mydb1 ~]# echo $c
a2c

Global variables export b = 2

[root@mydb1 ~]# w
 14:44:15 up 24 days, 23:49,  2 users,  load average: 0.07, 0.04, 0.00
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0    192.168.1.182    10:18    7:11   0.37s  0.37s -bash
root     pts/1    192.168.1.182    14:44    0.00s  0.03s  0.01s w
[root@mydb1 ~]# echo $SSH_TTY  查看当前终端的tty
/dev/pts/1

[root@localhost ~]# yum -y install psmisc
[root@localhost ~]# pstree
systemd─┬─NetworkManager───2*[{NetworkManager}]
        ├─VGAuthService
        ├─agetty
        ├─auditd───{auditd}
        ├─crond
        ├─dbus-daemon───{dbus-daemon}
        ├─firewalld───{firewalld}
        ├─master─┬─pickup
        │        └─qmgr
        ├─polkitd───6*[{polkitd}]
        ├─rsyslogd───2*[{rsyslogd}]
        ├─sshd───sshd───bash───pstree
        ├─systemd-journal
        ├─systemd-logind
        ├─systemd-udevd
        ├─tuned───4*[{tuned}]
        └─vmtoolsd
[root@localhost ~]# 
[root@localhost ~]# 
[root@localhost ~]# bash  //bash命令进入到子shell
[root@localhost ~]# pstree
systemd─┬─NetworkManager───2*[{NetworkManager}]
        ├─VGAuthService
        ├─agetty
        ├─auditd───{auditd}
        ├─crond
        ├─dbus-daemon───{dbus-daemon}
        ├─firewalld───{firewalld}
        ├─master─┬─pickup
        │        └─qmgr
        ├─polkitd───6*[{polkitd}]
        ├─rsyslogd───2*[{rsyslogd}]
        ├─sshd───sshd───bash───bash───pstree  //这里可以看出在子shell上执行了pstree命令
        ├─systemd-journal
        ├─systemd-logind
        ├─systemd-udevd
        ├─tuned───4*[{tuned}]
        └─vmtoolsd
[root@localhost ~]# a=linux  
[root@localhost ~]# echo $a
linux
[root@localhost ~]# bash
[root@localhost ~]# echo $a    非全局变量下，进入子shell,无法获取父shell中a=linux的值，这是因为在非全局变量下，当前定义的变量只在当前shell中生效，而不能在子shell生效

[root@localhost ~]# export b=123  父shell下定义全局变量 b=123，这样定义全局变量只在当前终端有效，重新打开新的终端无效。
[root@localhost ~]# echo $b      
123
[root@localhost ~]# bash         进入子shell，仍然可以获得父shell定义的b=123的值
[root@localhost ~]# echo $b
123
[root@localhost ~]# export c=456  在子shell中定义c=456
[root@localhost ~]# echo $c
456
[root@localhost ~]# exit    退出子shell进入父shell
exit
[root@localhost ~]# echo $c  在父shell中无法获得在子shell中定义c=456的值，父shell与子shell的关系是从上到下的，而不能从下到上

unset variables, cancel the assignment, unset b unset the variable name

7. environment variable configuration file

System-level environment variables, configuration files etc, takes effect globally.
- /etc/profile User environment variables, interactive, logged in execution, enter a user name, ip, port, password will automatically load, then the profile will automatically call bashrc.
- /etc/bashrc Users do not log in, execute the shell will take effect, just run the shell script, which is called bashrc configuration
User-level environment variable, in each user's home directory
- ~/.bashrc
- ~/.bash_profile . .bash_profile或者source .bash_profile
- ~/.bash_history
- ~/.bash_logout Some actions need to be made when a user-defined exit, such as: delete the command history when you exit, you can delete the command history command, on the inside .bash_logout
- PS1='\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;36m\]\w\[\033[00m\]\$ '
  - vim /etc/bashrc In the definition
    Three, DAY3

8. special symbols

* 任意个任意字符
? 任意一个字符
# 注释字符
\ 脱义字符 For c = '$ a $ b' result of $ a $ b in addition to single quotes, may also be used off signifier c = \ $ a \ $ b.
| 管道符

9. Several pipelines and related commands

cut 分割, -D -f delimiter specified block number of the specified number of characters -c

Demo:

[root@localhost ~]# cat /etc/passwd |head -2
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
[root@localhost ~]# cat /etc/passwd |head -2 |cut -d ":" -f 1
root
bin
[root@localhost ~]# cat /etc/passwd |head -2 |cut -d ":" -f 1,2
root:x
bin:x
[root@localhost ~]# cat /etc/passwd |head -2 |cut -d ":" -f 1,5
root:root
bin:bin
[root@localhost ~]# cat /etc/passwd |head -2 |cut -d ":" -f 1-5
root:x:0:0:root
bin:x:1:1:bin
[root@localhost ~]# cat /etc/passwd |head -2 |cut -c 4
t
:

sort 排序, -N -r reverse order to sort digital -t separator -kn1 / -kn1, n2

Demo:

[root@localhost ~]# cat /etc/passwd |head -4 |sort
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
root:x:0:0:root:/root:/bin/bash
[root@localhost ~]# cat /etc/passwd |head -4 |sort -n
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
root:x:0:0:root:/root:/bin/bash
[root@localhost ~]# cat /etc/passwd |head -4 |sort -nr
root:x:0:0:root:/root:/bin/bash
daemon:x:2:2:daemon:/sbin:/sbin/nologin
bin:x:1:1:bin:/bin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin

wc -l 统计行数 -w -m character counts statistics word

Show


[root@localhost ~]# cat 1.txt 内容有6个字符
123
abc
[root@localhost ~]# cat -A 1.txt 
123$
abc$
[root@localhost ~]# wc -m 1.txt  
8 1.txt   统计有8个字符，不要忘记隐藏的换行符

[root @ localhost ~] # CAT 1.txt
123
abc, F23
[root @ localhost ~] # 1.txt WC -w number of words statistics, separated by a space
3 1.txt

uniq 去重, -C count the number of rows
- Show
```
[root@localhost ~]# uniq 1.txt  直接uniq没有去重
123
abc  ,f23
123
abc
1
2
1
```
[root @ localhost ~] # sort 1.txt | uniq deduplication first sort, uniq typically used with Sort
. 1
123
2
ABC
ABC, F23

[root @ localhost ~] # sort 1.txt | uniq -c Sort go first and then re-count the number of rows
2 1
2 123
1 2
1 abc
1 abc, F23
tee 和 > 类似, While also redirect screen display
- Show
```
[root@localhost ~]# cat 1.txt 
123
abc  ,f23
123
abc
1
2
1
```
[root @ localhost ~] # sort 1.txt | uniq -c | tee a.txt | tee acts like>, but it will redirect the contents shown on the display screen
2. 1
2 123
. 1 2
. 1 ABC
. 1 abc, f23

[root@localhost ~]# sort 1.txt |uniq -c |tee -a a.txt |tee -a 相当于>>
2 1
2 123
1 2
1 abc
1 abc ,f23

[root@localhost ~]# cat a.txt
2 1
2 123
1 2
1 abc
1 abc ,f23
2 1
2 123
1 2
1 abc
1 abc ,f23

tr 替换字符, Tr 'a' 'b', replacing case tr '[az]' '[AZ]'

Show

[root@localhost ~]# echo "aminglinux" |tr 'a' 'A'   替换单个
Aminglinux
[root@localhost ~]# echo "aminglinux" |tr '[al]' '[AL]'  替换多个
AmingLinux
[root@localhost ~]# echo "aminglinux" |tr '[a-z]' '[A-Z]'  替换指定范围
AMINGLINUX
[root@localhost ~]# echo "aminglinux" |tr '[a-z]' '1'  也可以替换成数字
1111111111

split 切割, -B size (in bytes default), - l rows, -d numeric suffix is added

Show

[root@localhost test]# split -b 2M 2.txt 指定切割后每个文件的大小
[root@localhost test]# ls
2.txt  xaa  xab  xac  xad  xae
[root@localhost test]# ll -h
总用量 20M
-rw-r--r--. 1 root root  10M 2月  24 08:57 2.txt
-rw-r--r--. 1 root root 2.0M 2月  24 09:04 xaa
-rw-r--r--. 1 root root 2.0M 2月  24 09:04 xab
-rw-r--r--. 1 root root 2.0M 2月  24 09:04 xac
-rw-r--r--. 1 root root 2.0M 2月  24 09:04 xad
-rw-r--r--. 1 root root 2.0M 2月  24 09:04 xae
[root@localhost test]# split -b 2M 2.txt 2019.  指定切割后每个文件的大小以及文件的前缀
[root@localhost test]# ls
2019.aa  2019.ab  2019.ac  2019.ad  2019.ae  2.txt  xaa  xab  xac  xad  xae
[root@localhost test]# split -l 10000 2.txt 201911.   指定切割文件的行数以及文件的前缀
[root@localhost test]# ls
201911.aa  201911.ab  201911.ac  201911.ad  201911.ae  201911.af  201911.ag  201911.ah  2.txt

10.shell special symbols

$ Variable prefix! $ Combination, which represents the regular end of the line

; Multiple commands written line, separated by a semicolon

Show

[root@localhost test]# for i in `seq 1 10`
> do
> echo $i
> done
1
2
3
4
5
6
7
8
9
10
[root@localhost test]# for i in `seq 1 10`; do echo $i; done
[root@localhost test]# ls 2.txt ; wc -l 2.txt 
2.txt
77517 2.txt

~ User home behind a regular expression represented matcher
& Back into the command, the command will throw the background
> >> 2> 2>> &>
[ ] Of a specified character, [0-9], [a-zA-Z], [abc]
&& and ||, between a command
- Show
```
[root@localhost test]# ls 2.txt || wc -l 2.txt 
2.txt
[root@localhost test]# ls 2a.txt || wc -l 2.txt 
ls: 无法访问2a.txt: 没有那个文件或目录
77517 2.txt
|| 如果前面执行成功，就不执行后面。如果前面执行不成功，才会执行后面
```
[root @ localhost the Test] # LS 2a.txt the -l && WC 2.txt
LS: can not access 2a.txt: No such file or directory
[root @ localhost the Test] # LS 2.txt the -l && WC 2.txt
2 .txt
77517 2.txt
front unsuccessful implementation, will not be back to perform, execute successfully before, will be back to perform

[root @ localhost the Test] # [-d aminglinux] || mkdir aminglinux
[root @ localhost the Test] # LS
201911.aa 201911.ac 201911.ae 201911.ag 2.txt
201911.ab 201911.ad 201911.af 201 911. aminglinux AH
[root @ localhost the Test] # [-d aminglinux] && mkdir aminglinux
mkdir: can not create directory "aminglinux": file already exists

1 linux shell base

A, DAY1

1. What is the shell

2. Command History

3. Command completion and aliases

4. wildcard, input and output redirection

Two, DAY2

The job control pipe, and

6.shell variable

7. environment variable configuration file

Three, DAY3

8. special symbols

9. Several pipelines and related commands

10.shell special symbols

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