【BASH】笔记

1. 变量：

[root@yeyeck ~]# myname=yeyeck
[root@yeyeck ~]# echo $myname
yeyeck
[root@yeyeck ~]# echo ${myname}
yeyeck
[root@yeyeck ~]# line='my name is ${myname}'  <- 单引号不保留特定功能
[root@yeyeck ~]# echo $line
my name is ${myname}
[root@yeyeck ~]# line2="my name is ${myname}" <- 双引号保留特定功能
[root@yeyeck ~]# echo $line2
my name is yeyeck
[root@yeyeck ~]# 

2. 环境变量与子进程

    设置环境变量： export 变量名

　进入子进程： bash

　离开子进程：exit

[root@yeyeck ~]# myname=yeyeck  <- 定义一个普通变量
[root@yeyeck ~]# bash        <- 进入子进程
[root@yeyeck ~]# echo $myname  <- 在子进程中视图输出该变量， 无效

[root@yeyeck ~]# exit  <- 离开子进程
exit
[root@yeyeck ~]# echo $myname  <- 回到父进程，输出该变量，有效
yeyeck
[root@yeyeck ~]# export myname  <- 将该变量设置为环境变量
[root@yeyeck ~]# bash  <- 进入子进程
[root@yeyeck ~]# echo $myname  <- 在子进程中视图输出该变量， 生效
yeyeck
[root@yeyeck ~]# exit  <- 离开子进程
exit
[root@yeyeck ~]# unset myname  <- 清楚该变量
[root@yeyeck ~]# bash              
[root@yeyeck ~]# echo $myname  <- 子进程中无效

[root@yeyeck ~]# exit
exit
[root@yeyeck ~]# $myname      <- 父进程中也无效

3. 将命令运行结果 保存到变量中

　　两种方法，用反单引号 `命令` 或者 $(命令)

[root@yeyeck ~]# ifconfig
docker0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 172.17.0.1  netmask 255.255.0.0  broadcast 172.17.255.255
        ether 02:42:11:c4:23:5a  txqueuelen 0  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.18.122.194  netmask 255.255.240.0  broadcast 172.18.127.255
        ether 00:16:3e:02:23:2c  txqueuelen 1000  (Ethernet)
        RX packets 6370781  bytes 1439478547 (1.3 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 8320275  bytes 1025890184 (978.3 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 36  bytes 4896 (4.7 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 36  bytes 4896 (4.7 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@yeyeck ~]# 
[root@yeyeck ~]# 
[root@yeyeck ~]# 
[root@yeyeck ~]# 
[root@yeyeck ~]# 
[root@yeyeck ~]# ipInfo=$(ifconfig)
[root@yeyeck ~]# echo $ipInfo 
docker0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255 ether 02:42:11:c4:23:5a txqueuelen 0 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 172.18.122.194 netmask 255.255.240.0 broadcast 172.18.127.255 ether 00:16:3e:02:23:2c txqueuelen 1000 (Ethernet) RX packets 6370825 bytes 1439482437 (1.3 GiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 8320306 bytes 1025895604 (978.3 MiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 loop txqueuelen 1000 (Local Loopback) RX packets 36 bytes 4896 (4.7 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 36 bytes 4896 (4.7 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
[root@yeyeck ~]# 
[root@yeyeck ~]# 
[root@yeyeck ~]# ipInfo2=`ifconfig`
[root@yeyeck ~]# echo $ipInfo2
docker0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255 ether 02:42:11:c4:23:5a txqueuelen 0 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 172.18.122.194 netmask 255.255.240.0 broadcast 172.18.127.255 ether 00:16:3e:02:23:2c txqueuelen 1000 (Ethernet) RX packets 6370907 bytes 1439489387 (1.3 GiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 8320354 bytes 1025902656 (978.3 MiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 loop txqueuelen 1000 (Local Loopback) RX packets 36 bytes 4896 (4.7 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 36 bytes 4896 (4.7 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

4. 读取用户输入

　　read [-pt] variable

　　-p  后面可以接提示语句提示用户输入什么

　　-t  后面可以接等待的时间

[root@yeyeck ~]# read words
I am yeyeck
[root@yeyeck ~]# echo $words
I am yeyeck
[root@yeyeck ~]# read -p'who are you?'
who are you?yeyeck
[root@yeyeck ~]# echo $words
I am yeyeck
[root@yeyeck ~]# read -p'Please input your name: ' yourName
Please input your name: yeyeck
[root@yeyeck ~]# echo $yourName
yeyeck
[root@yeyeck ~]# read -p'Please input your age: ' -t 5  yourAge
Please input your age: 12
[root@yeyeck ~]# read -p'Please input your address: ' -t 5  yourAddr
Please input your address: [root@yeyeck ~]# <- 5s 内没有输入，等待结束
[root@yeyeck ~]# echo $yourAddr

[root@yeyeck ~]#