基本用法
read命令主要用于从标准输入读取内容或从文件中读取内容，并把信息保存到变量中。其常用用法如下所示：
read [选项] [文件]
| 选项 | 解释 |
|---|---|
| -a array | 将内容读取到数值中，变量默认为数组且以空格做为分割符 |
| -d delimiter | 遇到指定的字符即停止读取 |
| -n nchars | 指定最多可以读入的字符数，即定义输入文本的长度 |
| -r | 屏蔽转义符 |
| -p prompt | 显示提示信息 |
| -s | 静默模式，在输入字符时不在终端中显示，常用于密码输入等 |
| -t timeout | 指定超时时间 |
| -u FD | 从文件描述符中读入，该FD可以由exec开启 |
用法示例
1、从标准输入读入
[root@localhost test]# cat read.sh
#!/bin/bash
echo -n "Please input your name:"
read name
echo "Hello $name"
[root@localhost test]# bash read.sh
Please input your name:Jack
Hello Jack
2、指定显示信息从标准输入读入
[root@localhost test]# cat read.sh
#!/bin/bash
# echo -n "Please input your name:"
read -p "Please input your name:" name
# read name
echo "Hello $name"
[root@localhost test]# bash read.sh
Please input your name:Jack
Hello Jack
在以上示例中，read是一次可以接受多个参数的，如下所示：
read -p "Please input your name:" firstName secondName lastName
但需要注意的事项如下：
- 如果输入的数据少于变量个数，则多余的变量不会获取到数据，即变量值为空
- 如果输入的数据多于变量个数，则超出的数据将全部赋给最后一个变量
- 如果在read命令后面没有定义任何变量，脚本在执行时，如果用户输入数据，此时数据则保存到环境变量$REPLY中
3、指定超时时间
[root@localhost test]# cat read.sh
#!/bin/bash
if read -t 3 -p "Please input your name:" firstName secondName lastName
then
echo "variable is $firstName - $secondName - $lastName"
else
echo -e "\ntimeout\n"
fi
[root@localhost test]# bash read.sh
Please input your name:
timeout
4、从指定文件中读取内容
[root@localhost test]# cat -n test.txt
1 this is test text.
2 this is second line.
3 Hello world
4 C# Main
5 Python
# 使用-u选项
[root@localhost test]# cat readtest.sh
#!/bin/bash
exec 5< ~/test/test.txt
count=0
while read -u 5 var
do
let count=$count+1
echo "Line $count is $var"
done
echo "Total line count is $count"
exec 5<&-
[root@localhost test]# bash readtest.sh
Line 1 is this is test text.
Line 2 is this is second line.
Line 3 is Hello world
Line 4 is C# Main
Line 5 is Python
Total line count is 5
# 使用管道
[root@localhost test]# cat readtest.sh
#!/bin/bash
count=1
cat ~/test/test.txt | while read line
do
echo "Current line $count - $line "
let count=$count+1
done
echo "Total line count is $count"
[root@localhost test]# bash readtest.sh
Current line 1 - this is test text.
Current line 2 - this is second line.
Current line 3 - Hello world
Current line 4 - C# Main
Current line 5 - Python
Total line count is 1
# 使用重定向
[root@localhost test]# cat readtest.sh
#!/bin/bash
count=0
while read line
do
let count=$count+1
echo "Current line $count - $line "
done < ~/test/test.txt
echo "Total line count is $count"
[root@localhost test]# bash readtest.sh
Current line 1 - this is test text.
Current line 2 - this is second line.
Current line 3 - Hello world
Current line 4 - C# Main
Current line 5 - Python
Total line count is 5
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