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read
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===
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从键盘读取变量值
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## 补充说明
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**read命令** 从键盘读取变量的值，通常用在shell脚本中与用户进行交互的场合。该命令可以一次读取多个变量的值，变量和输入的值都需要使用空格隔开。在read命令后面，如果没有指定变量名，读取的数据将被自动赋值给特定的变量REPLY
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### 语法
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```
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read(选项)(参数)
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```
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### 选项
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```
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-p：指定读取值时的提示符；
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-t：指定读取值时等待的时间（秒）。
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```
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### 参数
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变量：指定读取值的变量名。
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### 实例
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下面的列表给出了read命令的常用方式：
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```
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read 1987name
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从标准输入读取输入并赋值给变量1987name。
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```
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```
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read first last
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从标准输入读取输入到第一个空格或者回车，将输入的第一个单词放到变量first中，并将该行其他的输入放在变量last中。
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```
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```
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read
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从标准输入读取一行并赋值给特定变量REPLY。
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```
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```
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read -a arrayname
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把单词清单读入arrayname的数组里。
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```
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```
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read -p "text"
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打印提示（text），等待输入，并将输入存储在REPLY中。
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```
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```
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read -r line
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允许输入包含反斜杠。
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```
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```
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read -t 3
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指定读取等待时间为3秒。
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```
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```
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read -n 2 var
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从输入中读取两个字符并存入变量var，不需要按回车读取。
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```
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```
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read -d ":" var
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用定界符“:”结束输入行。
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```
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## read命令示例
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从标准输入读取输入并赋值给变量1987name。
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```
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#read 1987name #等待读取输入，直到回车后表示输入完毕，并将输入赋值给变量answer
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HelloWorld #控制台输入Hello
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#echo $1987name #打印变量
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HelloWorld
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```
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等待一组输入，每个单词之间使用空格隔开，直到回车结束，并分别将单词依次赋值给这三个读入变量。
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```
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#read one two three
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1 2 3 #在控制台输入1 2 3，它们之间用空格隔开。
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#echo "one = $one, two = $two, three = $three"
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one = 1, two = 2, three = 3
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```
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REPLY示例
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```
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#read #等待控制台输入，并将结果赋值给特定内置变量REPLY。
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This is REPLY #在控制台输入该行。
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#echo $REPLY #打印输出特定内置变量REPLY，以确认是否被正确赋值。
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This is REPLY
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```
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-p选项示例
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```
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#read -p "Enter your name: " #输出文本提示，同时等待输入，并将结果赋值给REPLY。
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Enter you name: stephen #在提示文本之后输入stephen
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#echo $REPLY
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stephen
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```
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等待控制台输入，并将输入信息视为数组，赋值给数组变量friends，输入信息用空格隔开数组的每个元素。
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```
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#read -a friends
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Tim Tom Helen
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#echo "They are ${friends[0]}, ${friends[1]} and ${friends[2]}."
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They are Tim, Tom and Helen.
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```
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**补充一个终端输入密码时候，不让密码显示出来的例子。**
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方法1：
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```
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#!/bin/bash
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read -p "输入密码：" -s pwd
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echo
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echo password read, is "$pwd"
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```
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方法2：
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```
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#!/bin/bash
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stty -echo
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read -p "输入密码：" pwd
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stty echo
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echo
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echo 输入完毕。
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```
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其中，选项`-echo`禁止将输出发送到终端，而选项`echo`则允许发送输出。
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使用read命令从键盘读取变量值，并且将值赋给指定的变量，输入如下命令：
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```
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read v1 v3 #读取变量值
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```
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执行上面的指令以后，要求键入两个数据，如下所示：
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```
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Linux c+ #输入数据
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```
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完成之后，可以使用echo命令将指定的变量值输出查看，输入如下命令：
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```
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echo $v1 $v3 #输出变量的值
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```
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执行输出变量值的命令以后，将显示用户所输入的数据值，如下所示：
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```
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Linux c+ #输出变量值
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```
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注意：使用echo命令输出变量值时，必须在变量名前添加符号`$`。否则，echo将直接输出变量名。
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<!-- Linux命令行搜索引擎：https://jaywcjlove.github.io/linux-command/ -->
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