一、变量的命名

变量名必须以字母或下划线开头,由字母、数字、或下划线组成,变量名的长度不能超过255个字符。

二、变量的分类

1. 用户自定义变量

2. 环境变量

3. 位置参数变量

4. 预定义变量

三、用户自定义变量

用户自定义变量是“局部变量”,只能在当前的Shell中生效

1. 定义变量

变量名=变量值

示例:

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注意:等号前后不能有空格,否则会出现以下错误提示:

aaarticlea/png;base64,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" alt="" width="241" height="26" />

2. 变量调用

$变量名 或 ${变量名}

示例:

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3. 变量叠加

示例:

aaarticlea/png;base64,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" alt="" width="239" height="43" />

或:

aaarticlea/png;base64,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" alt="" width="223" height="43" />

4. 删除变量

unset 变量名

示例:

aaarticlea/png;base64,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" alt="" width="223" height="13" />

5. 查看变量

1) env:查看所有的环境变量

2) set:查看所有的变量(包括用户自定义变量)

四、环境变量

环境变量是“全局变量”,在当前Shell和这个Shell的所有子Shell中生效

1. 设置环境变量

export 变量名=变量值

变量名=变量值

export 变量名

示例:

aaarticlea/png;base64,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" alt="" width="274" height="63" />

注意:设置环境变量时,建议使用大写,避免与用户自定义变量或系统命令(都是小写的)冲突。

2. 删除环境变量,环境变量调用,查看环境变量

用户自定义变量的使用方式相同

3. 设置PS1环境变量

PS1环境变量会影响用户提示符信息,示例如下:

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alt="" width="323" height="56" />

五、位置变量

1. $n

n为数字,$0代表命令本身,$1-$9代表第一到第九个参数,十以上的参数需要用大括号包含,如${10}。

示例:

#!/bin/bash
a=$
b=$
sum=$(($a +$b))
echo $sum

2. $*

这个变量代表命令行中所有的参数,$*把所有的参数看成一个整体

#!/bin/bash
for i in "$*"
do
echo $i
done #运行:test.sh
#输出:
#解释:$*中的所有参数被看成是一个整体,所以这个for循环只会循环一次

3. $@

这个变量也代表命令行中所有的参数,不过$@把每个参数区分对待


#!/bin/bash
for i in "$@"
do
echo $i
done
#运行:test.sh 1 2 3
#输出: #解释:$@中的每个参数被看成独立的,所以这个for循环会循环多次

4. $#

这个变量代表命令行中的所有参数的个数

#!/bin/bash
echo $# #运行:test.sh
#输出:

六、预定义变量

1. $?

最后一次执行的命令的返回状态。如果这个值为0,则说明上一个命令执行正确;如果这个值不为0,则代表上一个命令执行的错误码。

示例:

aaarticlea/png;base64,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" alt="" width="223" height="96" />

2. $$

当前进程的进程号(PID)

示例:

aaarticlea/png;base64,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" alt="" width="226" height="24" />

3. $!

后台运行的最后一个进程的进程号(PID)

#!/bin/bash

find /root -name "test.sh" &
echo $!

七、read命令

接受键盘输入

1. 参数说明

-p "提示信息": 在等待read输入时,输出的提示信息

-t 秒数:read命令会一直等待用户输入,使用此参数可以指定等待时间

-n 字符数:read命令只接受指定的字符数,就会继续执行

-s : 隐藏输入的数据,适用于机密信息的输入

2. 示例

#!/bin/bash

read -p "please input username:" username
read -p "please input password:" -s password
echo -e "\n"
read -p "please input sex[F/M]:" -n sex
echo -e "\n"
echo "Welcome $username[$sex]"

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