|
|
|
|
@ -1,410 +1,410 @@
|
|
|
|
|
<h1><center>Shell变量</center></h1>
|
|
|
|
|
|
|
|
|
|
作者：行癫（盗版必究）
|
|
|
|
|
|
|
|
|
|
------
|
|
|
|
|
|
|
|
|
|
## 一：变量概述
|
|
|
|
|
|
|
|
|
|
#### 1.什么是变量
|
|
|
|
|
|
|
|
|
|
变量来源于数学，是计算机语言中能储存计算结果或能表示值的抽象概念
|
|
|
|
|
|
|
|
|
|
变量可以通过变量名访问，在指令式语言中，变量通常是可变的；在某些条件下也是不可变的
|
|
|
|
|
|
|
|
|
|
#### 2.变量的规则
|
|
|
|
|
|
|
|
|
|
命名只能使用英文字母，数字和下划线，首个字符不能以数字开头
|
|
|
|
|
|
|
|
|
|
中间不能有空格，可以使用下划线
|
|
|
|
|
|
|
|
|
|
不能使用标点符号
|
|
|
|
|
|
|
|
|
|
不能使用bash里的关键字
|
|
|
|
|
|
|
|
|
|
## 二：变量分类
|
|
|
|
|
|
|
|
|
|
#### 1.自定义变量
|
|
|
|
|
|
|
|
|
|
定义变量：变量名=变量值 例如：xingdian=123
|
|
|
|
|
|
|
|
|
|
引用变量：$变量名 或 ${变量名}
|
|
|
|
|
|
|
|
|
|
查看变量：echo $变量名
|
|
|
|
|
|
|
|
|
|
取消变量：unset 变量名
|
|
|
|
|
|
|
|
|
|
作用范围：仅在当前shell中有效
|
|
|
|
|
|
|
|
|
|
#### 2.环境变量
|
|
|
|
|
|
|
|
|
|
定义环境变量：
|
|
|
|
|
|
|
|
|
|
方法一 export back_dir2=/home/backup
|
|
|
|
|
|
|
|
|
|
方法二 export back_dir1 将自定义变量转换成环境变量
|
|
|
|
|
|
|
|
|
|
引用环境变量：$变量名 或 ${变量名}
|
|
|
|
|
|
|
|
|
|
查看环境变量：echo $变量名
|
|
|
|
|
|
|
|
|
|
取消环境变量：unset 变量名
|
|
|
|
|
|
|
|
|
|
变量作用范围：在当前shell和子shell有效
|
|
|
|
|
|
|
|
|
|
注意：
|
|
|
|
|
|
|
|
|
|
环境变量拥有可继承性：export之后就拥有继承性
|
|
|
|
|
|
|
|
|
|
永久生效：写到环境变量脚本，/etc/profile ~/.baserc ~/.bash_profile /etc/bashrc
|
|
|
|
|
|
|
|
|
|
案例：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# vim /etc/profile
|
|
|
|
|
JAVA_HOME=/usr/local/java
|
|
|
|
|
PATH=$JAVA_HOME/bin:$PATH
|
|
|
|
|
export JAVA_HOME PATH
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# vim ~/.bash_profile (只显示部分)
|
|
|
|
|
PATH=$PATH:$HOME/bin:/usr/local/mycat/bin
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
/etc/profile
|
|
|
|
|
|
|
|
|
|
这是系统最主要的shell设置文件，也是用户登陆时系统最先检查的文件，有关重要的环境变量都定义在此，其中包括PATH,USER,LOGNAME,MAIL,HOSTNAME,HISTSIZE,INPUTRC等。而在文件的最后，它会检查并执行/etc/profile.d/*.sh的脚本
|
|
|
|
|
|
|
|
|
|
~/.bash_profile
|
|
|
|
|
|
|
|
|
|
这个文件是每位用户的bash环境设置文件，它存在与于用户的主目录中，当系统执行/etc/profile 后，就会接着读取此文件内的设置值。在此文件中会定义USERNAME,BASH_ENV和PATH等环境变量，但是此处PATH除了包含系统的$PATH变量外加入用户的“bin”目录路径
|
|
|
|
|
|
|
|
|
|
~/.bashrc
|
|
|
|
|
|
|
|
|
|
接下来系统会检查~.bashrc文件，这个文件和前两个文件（/etc/profile 和~.bash_profile）最大的不同是，每次执行bash时，~.bashrc都会被再次读取，也就是变量会再次地设置，而/etc/profile,~./bash_profile只有在登陆时才读取。就是因为要经常的读取，所以~/.bashrc文件只定义一些终端机设置以及shell提示符号等功能，而不是定义环境变量
|
|
|
|
|
|
|
|
|
|
~/.bash_login
|
|
|
|
|
|
|
|
|
|
如果~/.bash_profile文件不存在，则系统会转而读取~/.bash_login这个文件内容。这是用户的登陆文件，在每次用户登陆系统时，bash都会读此内容，所以通常都会将登陆后必须执行的命令放在这个文件中
|
|
|
|
|
|
|
|
|
|
.profile
|
|
|
|
|
|
|
|
|
|
如果~./bash_profile ~./bash_login两个文件都不存在，则会使用这个文件的设置内容，其实它的功能与~/.bash_profile相同
|
|
|
|
|
|
|
|
|
|
.bash_logout
|
|
|
|
|
|
|
|
|
|
如果想在注销shell前执行一些工作，都可以在此文件中设置
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# vi ~.bash_logout
|
|
|
|
|
clear
|
|
|
|
|
仅执行一个clear命令在你注销的时候
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
~/.bash_history
|
|
|
|
|
|
|
|
|
|
这个文件会记录用户先前使用的历史命令
|
|
|
|
|
|
|
|
|
|
注意：
|
|
|
|
|
|
|
|
|
|
在/etc/profile.d建立独立的环境变量配置文件
|
|
|
|
|
|
|
|
|
|
常用环境变量：USER UID HOME HOSTNAME PWD PATH
|
|
|
|
|
|
|
|
|
|
PATH：这个变量存放的是所有命令所在的路径 修改：PATH=$PATH:+目录
|
|
|
|
|
|
|
|
|
|
#### 3.位置变量
|
|
|
|
|
|
|
|
|
|
$1 $2 $3 $4 $5 $6 $7 $8 $9 ${10}
|
|
|
|
|
|
|
|
|
|
案例：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud sh]# cat xingdian.sh
|
|
|
|
|
#!/bin/bash
|
|
|
|
|
echo "hello $1"
|
|
|
|
|
[root@xingdiancloud sh]# bash xingdian.sh xingdian
|
|
|
|
|
hello xingdian
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
4.预定义变量
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
$0 脚本名
|
|
|
|
|
$* 所有的参数
|
|
|
|
|
$@ 所有的参数
|
|
|
|
|
$# 参数的个数
|
|
|
|
|
$$ 当前进程的PID
|
|
|
|
|
$! 上一个后台进程的PID
|
|
|
|
|
$? 上一个命令的返回值 0表示成功
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
案例：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud sh]# cat test.sh
|
|
|
|
|
#!/bin/bash
|
|
|
|
|
echo "第2个位置参数是$2"
|
|
|
|
|
echo "第1个位置参数是$1"
|
|
|
|
|
echo "第4个位置参数是$4"
|
|
|
|
|
|
|
|
|
|
echo "所有参数是: $*"
|
|
|
|
|
echo "所有参数是: $@"
|
|
|
|
|
echo "参数的个数是: $#"
|
|
|
|
|
echo "当前进程的PID是: $$"
|
|
|
|
|
|
|
|
|
|
echo '$1='$1
|
|
|
|
|
echo '$2='$2
|
|
|
|
|
echo '$3='$3
|
|
|
|
|
echo '$*='$*
|
|
|
|
|
echo '$@='$@
|
|
|
|
|
echo '$#='$#
|
|
|
|
|
echo '$$='$$
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
## 三：变量赋值
|
|
|
|
|
|
|
|
|
|
#### 1.显示赋值
|
|
|
|
|
|
|
|
|
|
变量名=变量值
|
|
|
|
|
|
|
|
|
|
示例：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# ip1=192.168.1.251
|
|
|
|
|
[root@xingdiancloud ~]# school="BeiJing 1000phone"
|
|
|
|
|
[root@xingdiancloud ~]# today1=`date +%F`
|
|
|
|
|
[root@xingdiancloud ~]# today2=$(date +%F)
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
#### 2.键盘读入
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
read 变量名
|
|
|
|
|
read -p "提示信息: " 变量名
|
|
|
|
|
read -t 5 -p "提示信息: " 变量名 -t 后面跟秒数，定义输入字符的等待时间
|
|
|
|
|
read -n 2 变量名 -n 后跟一个数字，定义输入文本的长度，很实用。
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
案例1：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# vim first.sh
|
|
|
|
|
back_dir1=/var/backup
|
|
|
|
|
read -p "请输入你的备份目录: " back_dir2
|
|
|
|
|
echo $back_dir1
|
|
|
|
|
echo $back_dir2
|
|
|
|
|
[root@xingdiancloud ~]# sh first.sh
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
案例2：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# vim ping2.sh
|
|
|
|
|
#!/bin/bash
|
|
|
|
|
read -p "Input IP: " ip
|
|
|
|
|
ping -c2 $ip &>/dev/null
|
|
|
|
|
if [ $? = 0 ];then
|
|
|
|
|
echo "host $ip is ok"
|
|
|
|
|
else
|
|
|
|
|
echo "host $ip is fail"
|
|
|
|
|
fi
|
|
|
|
|
[root@xingdiancloud ~]# chmod a+x ping2.sh
|
|
|
|
|
[root@xingdiancloud ~]# ./ping.sh
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
注意：定义或引用变量时注意事项
|
|
|
|
|
|
|
|
|
|
" " 弱引用 可以实现变量和命令的替换
|
|
|
|
|
|
|
|
|
|
' ' 强引用 不完成变量替换
|
|
|
|
|
|
|
|
|
|
反引 命令替换 等价于 $() 反引号中的shell命令会被先执行
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# school=1000phone
|
|
|
|
|
[root@xingdiancloud ~]# echo "${school} is good"
|
|
|
|
|
1000phone is good
|
|
|
|
|
[root@xingdiancloud ~]# echo '${school} is good'
|
|
|
|
|
${school} is good
|
|
|
|
|
[root@xingdiancloud ~]# touch `date +%F`_file1.txt
|
|
|
|
|
[root@xingdiancloud ~]# touch $(date +%F)_file2.txt
|
|
|
|
|
[root@xingdiancloud ~]# disk_free3="df -Ph |grep '/$' |awk '{print $4}'" 错误
|
|
|
|
|
[root@xingdiancloud ~]# disk_free4=$(df -Ph |grep '/$' |awk '{print $4}')
|
|
|
|
|
[root@xingdiancloud ~]# disk_free5=`df -Ph |grep '/$' |awk '{print $4}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
## 四：变量运算
|
|
|
|
|
|
|
|
|
|
#### 1.整数运算
|
|
|
|
|
|
|
|
|
|
方法一：expr
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# expr 1 + 2
|
|
|
|
|
[root@xingdiancloud ~]# expr $num1 + $num2 + - \* / %
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
方法二：$(())
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo $(($num1+$num2)) + - * / %
|
|
|
|
|
[root@xingdiancloud ~]# echo $((num1+num2))
|
|
|
|
|
[root@xingdiancloud ~]# echo $((5-3*2))
|
|
|
|
|
[root@xingdiancloud ~]# echo $(((5-3)*2))
|
|
|
|
|
[root@xingdiancloud ~]# echo $((2**3))
|
|
|
|
|
[root@xingdiancloud ~]# sum=$((1+2)); echo $sum
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
方法三：$[]
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo $[5+2] + - * / %
|
|
|
|
|
[root@xingdiancloud ~]# echo $[5**2]
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
方法四：let
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
[root@xingdiancloud ~]# let sum=2+3; echo $sum
|
|
|
|
|
[root@xingdiancloud ~]# let i++; echo $i
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
#### 2.小数运算
|
|
|
|
|
|
|
|
|
|
使用bc做小数运算，scale指定小数点位数
|
|
|
|
|
|
|
|
|
|
加法运算(scale参数无效)
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo "5.999 + 5.001"|bc
|
|
|
|
|
6.000
|
|
|
|
|
[root@xingdiancloud ~]# echo "5.111+ 5.1114"|bc
|
|
|
|
|
10.2224
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
减法运算(scale参数无效)
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo "2.22 - 1.11"|bc
|
|
|
|
|
1.11
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
乘法运算
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo "5.12 * 5.6000"|bc
|
|
|
|
|
28.6720
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
注意：乘积小数点位数默认以乘数中小数点位数最多的为准（不指定scale参数）
|
|
|
|
|
|
|
|
|
|
除法运算
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo "scale=2;9.898 / 1.11"|bc
|
|
|
|
|
8.91
|
|
|
|
|
[root@xingdiancloud ~]# echo "9.898 / 1.11"|bc
|
|
|
|
|
8
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
## 五：扩展
|
|
|
|
|
|
|
|
|
|
#### 1.内容的删除
|
|
|
|
|
|
|
|
|
|
案例一
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# url=www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${#url} 获取变量值的长度
|
|
|
|
|
15
|
|
|
|
|
[root@xingdian ~]# echo ${url} 标准查看
|
|
|
|
|
www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url#*.} 从前往后，最短匹配
|
|
|
|
|
sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url##*.} 从前往后，最长匹配 贪婪匹配
|
|
|
|
|
cn
|
|
|
|
|
[root@xingdian ~]# url=www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url#a.}
|
|
|
|
|
www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url#*sina.}
|
|
|
|
|
com.cn
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
案例二
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# url=www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url}
|
|
|
|
|
www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url%.*} 从后往前，最短匹配
|
|
|
|
|
www.sina.com
|
|
|
|
|
[root@xingdian ~]# echo ${url%%.*} 从后往前，最长匹配 贪婪匹配
|
|
|
|
|
www
|
|
|
|
|
[root@xingdian ~]# echo $HOSTNAME
|
|
|
|
|
xingdian.1000phone.com
|
|
|
|
|
[root@xingdian ~]# echo ${HOSTNAME%%.*}
|
|
|
|
|
xingdian
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
#### 2.索引及切片
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# echo ${url:0:5}
|
|
|
|
|
0:从头开始
|
|
|
|
|
5:到第五个
|
|
|
|
|
[root@xingdian ~]# echo ${url:5:5}
|
|
|
|
|
[root@xingdian ~]# echo ${url:5}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
#### 3.变量内容替换
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# url=www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url/sina/baidu}
|
|
|
|
|
www.baidu.com.cn
|
|
|
|
|
[root@xingdian ~]# url=www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url/n/N}
|
|
|
|
|
www.siNa.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url//n/N} 贪婪匹配
|
|
|
|
|
www.siNa.com.cN
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
#### 4.自增运算
|
|
|
|
|
|
|
|
|
|
对变量的值的影响
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# i=1
|
|
|
|
|
[root@xingdian ~]# let i++
|
|
|
|
|
[root@xingdian ~]# echo $i
|
|
|
|
|
2
|
|
|
|
|
[root@xingdian ~]# j=1
|
|
|
|
|
[root@xingdian ~]# let ++j
|
|
|
|
|
[root@xingdian ~]# echo $j
|
|
|
|
|
2
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
对表达式的值的影响
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# unset i
|
|
|
|
|
[root@xingdian ~]# unset j
|
|
|
|
|
[root@xingdian ~]#
|
|
|
|
|
[root@xingdian ~]# i=1
|
|
|
|
|
[root@xingdian ~]# j=1
|
|
|
|
|
[root@xingdian ~]#
|
|
|
|
|
[root@xingdian ~]# let x=i++ 先赋值，再运算
|
|
|
|
|
[root@xingdian ~]# let y=++j 先运算，再赋值
|
|
|
|
|
[root@xingdian ~]#
|
|
|
|
|
[root@xingdian ~]# echo $i
|
|
|
|
|
2
|
|
|
|
|
[root@xingdian ~]# echo $j
|
|
|
|
|
2
|
|
|
|
|
[root@xingdian ~]#
|
|
|
|
|
[root@xingdian ~]# echo $x
|
|
|
|
|
1
|
|
|
|
|
[root@xingdian ~]# echo $y
|
|
|
|
|
2
|
|
|
|
|
```
|
|
|
|
|
<h1><center>Shell变量</center></h1>
|
|
|
|
|
|
|
|
|
|
作者：行癫（盗版必究）
|
|
|
|
|
|
|
|
|
|
------
|
|
|
|
|
|
|
|
|
|
## 一：变量概述
|
|
|
|
|
|
|
|
|
|
#### 1.什么是变量
|
|
|
|
|
|
|
|
|
|
变量来源于数学，是计算机语言中能储存计算结果或能表示值的抽象概念
|
|
|
|
|
|
|
|
|
|
变量可以通过变量名访问，在指令式语言中，变量通常是可变的；在某些条件下也是不可变的
|
|
|
|
|
|
|
|
|
|
#### 2.变量的规则
|
|
|
|
|
|
|
|
|
|
命名只能使用英文字母，数字和下划线，首个字符不能以数字开头
|
|
|
|
|
|
|
|
|
|
中间不能有空格，可以使用下划线
|
|
|
|
|
|
|
|
|
|
不能使用标点符号
|
|
|
|
|
|
|
|
|
|
不能使用bash里的关键字
|
|
|
|
|
|
|
|
|
|
## 二：变量分类
|
|
|
|
|
|
|
|
|
|
#### 1.自定义变量
|
|
|
|
|
|
|
|
|
|
定义变量：变量名=变量值 例如：xingdian=123
|
|
|
|
|
|
|
|
|
|
引用变量：$变量名 或 ${变量名}
|
|
|
|
|
|
|
|
|
|
查看变量：echo $变量名
|
|
|
|
|
|
|
|
|
|
取消变量：unset 变量名
|
|
|
|
|
|
|
|
|
|
作用范围：仅在当前shell中有效
|
|
|
|
|
|
|
|
|
|
#### 2.环境变量
|
|
|
|
|
|
|
|
|
|
定义环境变量：
|
|
|
|
|
|
|
|
|
|
方法一 export back_dir2=/home/backup
|
|
|
|
|
|
|
|
|
|
方法二 export back_dir1 将自定义变量转换成环境变量
|
|
|
|
|
|
|
|
|
|
引用环境变量：$变量名 或 ${变量名}
|
|
|
|
|
|
|
|
|
|
查看环境变量：echo $变量名
|
|
|
|
|
|
|
|
|
|
取消环境变量：unset 变量名
|
|
|
|
|
|
|
|
|
|
变量作用范围：在当前shell和子shell有效
|
|
|
|
|
|
|
|
|
|
注意：
|
|
|
|
|
|
|
|
|
|
环境变量拥有可继承性：export之后就拥有继承性
|
|
|
|
|
|
|
|
|
|
永久生效：写到环境变量脚本，/etc/profile ~/.baserc ~/.bash_profile /etc/bashrc
|
|
|
|
|
|
|
|
|
|
案例：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# vim /etc/profile
|
|
|
|
|
JAVA_HOME=/usr/local/java
|
|
|
|
|
PATH=$JAVA_HOME/bin:$PATH
|
|
|
|
|
export JAVA_HOME PATH
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# vim ~/.bash_profile (只显示部分)
|
|
|
|
|
PATH=$PATH:$HOME/bin:/usr/local/mycat/bin
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
/etc/profile
|
|
|
|
|
|
|
|
|
|
这是系统最主要的shell设置文件，也是用户登陆时系统最先检查的文件，有关重要的环境变量都定义在此，其中包括PATH,USER,LOGNAME,MAIL,HOSTNAME,HISTSIZE,INPUTRC等。而在文件的最后，它会检查并执行/etc/profile.d/*.sh的脚本
|
|
|
|
|
|
|
|
|
|
~/.bash_profile
|
|
|
|
|
|
|
|
|
|
这个文件是每位用户的bash环境设置文件，它存在与于用户的主目录中，当系统执行/etc/profile 后，就会接着读取此文件内的设置值。在此文件中会定义USERNAME,BASH_ENV和PATH等环境变量，但是此处PATH除了包含系统的$PATH变量外加入用户的“bin”目录路径
|
|
|
|
|
|
|
|
|
|
~/.bashrc
|
|
|
|
|
|
|
|
|
|
接下来系统会检查~.bashrc文件，这个文件和前两个文件（/etc/profile 和~.bash_profile）最大的不同是，每次执行bash时，~.bashrc都会被再次读取，也就是变量会再次地设置，而/etc/profile,~./bash_profile只有在登陆时才读取。就是因为要经常的读取，所以~/.bashrc文件只定义一些终端机设置以及shell提示符号等功能，而不是定义环境变量
|
|
|
|
|
|
|
|
|
|
~/.bash_login
|
|
|
|
|
|
|
|
|
|
如果~/.bash_profile文件不存在，则系统会转而读取~/.bash_login这个文件内容。这是用户的登陆文件，在每次用户登陆系统时，bash都会读此内容，所以通常都会将登陆后必须执行的命令放在这个文件中
|
|
|
|
|
|
|
|
|
|
.profile
|
|
|
|
|
|
|
|
|
|
如果~./bash_profile ~./bash_login两个文件都不存在，则会使用这个文件的设置内容，其实它的功能与~/.bash_profile相同
|
|
|
|
|
|
|
|
|
|
.bash_logout
|
|
|
|
|
|
|
|
|
|
如果想在注销shell前执行一些工作，都可以在此文件中设置
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# vi ~.bash_logout
|
|
|
|
|
clear
|
|
|
|
|
仅执行一个clear命令在你注销的时候
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
~/.bash_history
|
|
|
|
|
|
|
|
|
|
这个文件会记录用户先前使用的历史命令
|
|
|
|
|
|
|
|
|
|
注意：
|
|
|
|
|
|
|
|
|
|
在/etc/profile.d建立独立的环境变量配置文件
|
|
|
|
|
|
|
|
|
|
常用环境变量：USER UID HOME HOSTNAME PWD PATH
|
|
|
|
|
|
|
|
|
|
PATH：这个变量存放的是所有命令所在的路径 修改：PATH=$PATH:+目录
|
|
|
|
|
|
|
|
|
|
#### 3.位置变量
|
|
|
|
|
|
|
|
|
|
$1 $2 $3 $4 $5 $6 $7 $8 $9 $10
|
|
|
|
|
|
|
|
|
|
案例：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud sh]# cat xingdian.sh
|
|
|
|
|
#!/bin/bash
|
|
|
|
|
echo "hello $1"
|
|
|
|
|
[root@xingdiancloud sh]# bash xingdian.sh xingdian
|
|
|
|
|
hello xingdian
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
4.预定义变量
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
$0 脚本名
|
|
|
|
|
$* 所有的参数
|
|
|
|
|
$@ 所有的参数
|
|
|
|
|
$# 参数的个数
|
|
|
|
|
$$ 当前进程的PID
|
|
|
|
|
$! 上一个后台进程的PID
|
|
|
|
|
$? 上一个命令的返回值 0表示成功
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
案例：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud sh]# cat test.sh
|
|
|
|
|
#!/bin/bash
|
|
|
|
|
echo "第2个位置参数是$2"
|
|
|
|
|
echo "第1个位置参数是$1"
|
|
|
|
|
echo "第4个位置参数是$4"
|
|
|
|
|
|
|
|
|
|
echo "所有参数是: $*"
|
|
|
|
|
echo "所有参数是: $@"
|
|
|
|
|
echo "参数的个数是: $#"
|
|
|
|
|
echo "当前进程的PID是: $$"
|
|
|
|
|
|
|
|
|
|
echo '$1='$1
|
|
|
|
|
echo '$2='$2
|
|
|
|
|
echo '$3='$3
|
|
|
|
|
echo '$*='$*
|
|
|
|
|
echo '$@='$@
|
|
|
|
|
echo '$#='$#
|
|
|
|
|
echo '$$='$$
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
## 三：变量赋值
|
|
|
|
|
|
|
|
|
|
#### 1.显示赋值
|
|
|
|
|
|
|
|
|
|
变量名=变量值
|
|
|
|
|
|
|
|
|
|
示例：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# ip1=192.168.1.251
|
|
|
|
|
[root@xingdiancloud ~]# school="BeiJing 1000phone"
|
|
|
|
|
[root@xingdiancloud ~]# today1=`date +%F`
|
|
|
|
|
[root@xingdiancloud ~]# today2=$(date +%F)
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
#### 2.键盘读入
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
read 变量名
|
|
|
|
|
read -p "提示信息: " 变量名
|
|
|
|
|
read -t 5 -p "提示信息: " 变量名 -t 后面跟秒数，定义输入字符的等待时间
|
|
|
|
|
read -n 2 变量名 -n 后跟一个数字，定义输入文本的长度，很实用。
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
案例1：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# vim first.sh
|
|
|
|
|
back_dir1=/var/backup
|
|
|
|
|
read -p "请输入你的备份目录: " back_dir2
|
|
|
|
|
echo $back_dir1
|
|
|
|
|
echo $back_dir2
|
|
|
|
|
[root@xingdiancloud ~]# sh first.sh
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
案例2：
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# vim ping2.sh
|
|
|
|
|
#!/bin/bash
|
|
|
|
|
read -p "Input IP: " ip
|
|
|
|
|
ping -c2 $ip &>/dev/null
|
|
|
|
|
if [ $? = 0 ];then
|
|
|
|
|
echo "host $ip is ok"
|
|
|
|
|
else
|
|
|
|
|
echo "host $ip is fail"
|
|
|
|
|
fi
|
|
|
|
|
[root@xingdiancloud ~]# chmod a+x ping2.sh
|
|
|
|
|
[root@xingdiancloud ~]# ./ping.sh
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
注意：定义或引用变量时注意事项
|
|
|
|
|
|
|
|
|
|
" " 弱引用 可以实现变量和命令的替换
|
|
|
|
|
|
|
|
|
|
' ' 强引用 不完成变量替换
|
|
|
|
|
|
|
|
|
|
反引 命令替换 等价于 $() 反引号中的shell命令会被先执行
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# school=1000phone
|
|
|
|
|
[root@xingdiancloud ~]# echo "${school} is good"
|
|
|
|
|
1000phone is good
|
|
|
|
|
[root@xingdiancloud ~]# echo '${school} is good'
|
|
|
|
|
${school} is good
|
|
|
|
|
[root@xingdiancloud ~]# touch `date +%F`_file1.txt
|
|
|
|
|
[root@xingdiancloud ~]# touch $(date +%F)_file2.txt
|
|
|
|
|
[root@xingdiancloud ~]# disk_free3="df -Ph |grep '/$' |awk '{print $4}'" 错误
|
|
|
|
|
[root@xingdiancloud ~]# disk_free4=$(df -Ph |grep '/$' |awk '{print $4}')
|
|
|
|
|
[root@xingdiancloud ~]# disk_free5=`df -Ph |grep '/$' |awk '{print $4}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
## 四：变量运算
|
|
|
|
|
|
|
|
|
|
#### 1.整数运算
|
|
|
|
|
|
|
|
|
|
方法一：expr
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# expr 1 + 2
|
|
|
|
|
[root@xingdiancloud ~]# expr $num1 + $num2 + - \* / %
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
方法二：$(())
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo $(($num1+$num2)) + - * / %
|
|
|
|
|
[root@xingdiancloud ~]# echo $((num1+num2))
|
|
|
|
|
[root@xingdiancloud ~]# echo $((5-3*2))
|
|
|
|
|
[root@xingdiancloud ~]# echo $(((5-3)*2))
|
|
|
|
|
[root@xingdiancloud ~]# echo $((2**3))
|
|
|
|
|
[root@xingdiancloud ~]# sum=$((1+2)); echo $sum
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
方法三：$[]
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo $[5+2] + - * / %
|
|
|
|
|
[root@xingdiancloud ~]# echo $[5**2]
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
方法四：let
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
[root@xingdiancloud ~]# let sum=2+3; echo $sum
|
|
|
|
|
[root@xingdiancloud ~]# let i++; echo $i
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
#### 2.小数运算
|
|
|
|
|
|
|
|
|
|
使用bc做小数运算，scale指定小数点位数
|
|
|
|
|
|
|
|
|
|
加法运算(scale参数无效)
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo "5.999 + 5.001"|bc
|
|
|
|
|
6.000
|
|
|
|
|
[root@xingdiancloud ~]# echo "5.111+ 5.1114"|bc
|
|
|
|
|
10.2224
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
减法运算(scale参数无效)
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo "2.22 - 1.11"|bc
|
|
|
|
|
1.11
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
乘法运算
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo "5.12 * 5.6000"|bc
|
|
|
|
|
28.6720
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
注意：乘积小数点位数默认以乘数中小数点位数最多的为准（不指定scale参数）
|
|
|
|
|
|
|
|
|
|
除法运算
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdiancloud ~]# echo "scale=2;9.898 / 1.11"|bc
|
|
|
|
|
8.91
|
|
|
|
|
[root@xingdiancloud ~]# echo "9.898 / 1.11"|bc
|
|
|
|
|
8
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
## 五：扩展
|
|
|
|
|
|
|
|
|
|
#### 1.内容的删除
|
|
|
|
|
|
|
|
|
|
案例一
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# url=www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${#url} 获取变量值的长度
|
|
|
|
|
15
|
|
|
|
|
[root@xingdian ~]# echo ${url} 标准查看
|
|
|
|
|
www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url#*.} 从前往后，最短匹配
|
|
|
|
|
sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url##*.} 从前往后，最长匹配 贪婪匹配
|
|
|
|
|
cn
|
|
|
|
|
[root@xingdian ~]# url=www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url#a.}
|
|
|
|
|
www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url#*sina.}
|
|
|
|
|
com.cn
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
案例二
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# url=www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url}
|
|
|
|
|
www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url%.*} 从后往前，最短匹配
|
|
|
|
|
www.sina.com
|
|
|
|
|
[root@xingdian ~]# echo ${url%%.*} 从后往前，最长匹配 贪婪匹配
|
|
|
|
|
www
|
|
|
|
|
[root@xingdian ~]# echo $HOSTNAME
|
|
|
|
|
xingdian.1000phone.com
|
|
|
|
|
[root@xingdian ~]# echo ${HOSTNAME%%.*}
|
|
|
|
|
xingdian
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
#### 2.索引及切片
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# echo ${url:0:5}
|
|
|
|
|
0:从头开始
|
|
|
|
|
5:到第五个
|
|
|
|
|
[root@xingdian ~]# echo ${url:5:5}
|
|
|
|
|
[root@xingdian ~]# echo ${url:5}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
#### 3.变量内容替换
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# url=www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url/sina/baidu}
|
|
|
|
|
www.baidu.com.cn
|
|
|
|
|
[root@xingdian ~]# url=www.sina.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url/n/N}
|
|
|
|
|
www.siNa.com.cn
|
|
|
|
|
[root@xingdian ~]# echo ${url//n/N} 贪婪匹配
|
|
|
|
|
www.siNa.com.cN
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
#### 4.自增运算
|
|
|
|
|
|
|
|
|
|
对变量的值的影响
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# i=1
|
|
|
|
|
[root@xingdian ~]# let i++
|
|
|
|
|
[root@xingdian ~]# echo $i
|
|
|
|
|
2
|
|
|
|
|
[root@xingdian ~]# j=1
|
|
|
|
|
[root@xingdian ~]# let ++j
|
|
|
|
|
[root@xingdian ~]# echo $j
|
|
|
|
|
2
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
对表达式的值的影响
|
|
|
|
|
|
|
|
|
|
```shell
|
|
|
|
|
[root@xingdian ~]# unset i
|
|
|
|
|
[root@xingdian ~]# unset j
|
|
|
|
|
[root@xingdian ~]#
|
|
|
|
|
[root@xingdian ~]# i=1
|
|
|
|
|
[root@xingdian ~]# j=1
|
|
|
|
|
[root@xingdian ~]#
|
|
|
|
|
[root@xingdian ~]# let x=i++ 先赋值，再运算
|
|
|
|
|
[root@xingdian ~]# let y=++j 先运算，再赋值
|
|
|
|
|
[root@xingdian ~]#
|
|
|
|
|
[root@xingdian ~]# echo $i
|
|
|
|
|
2
|
|
|
|
|
[root@xingdian ~]# echo $j
|
|
|
|
|
2
|
|
|
|
|
[root@xingdian ~]#
|
|
|
|
|
[root@xingdian ~]# echo $x
|
|
|
|
|
1
|
|
|
|
|
[root@xingdian ~]# echo $y
|
|
|
|
|
2
|
|
|
|
|
```
|
|
|
|
|
|
