Linux read命令详解

1.最简单的read，从标准输入读取，将结果保存在变量REPLY中

# read?
haha
# echo $REPLY
haha
#?

2.read从标准输入读取一行数据，并将其split，再将split后的字段赋值给read命令最后指定的变量，
第一个字段赋值给第一个变量，第二个字段赋值给第二个变量，以此类推。
下面的例子中，从标准输入读取一行，split后将第一个字段的值赋值给yourname变量，即Gilbert，
将第二个字段的值赋值给yourage变量，即30，split默认的分隔符是IFS变量的值，这个值默认是空格

# read yourname yourage
Gilbert 30
# echo $yourname
Gilbert
# echo $yourage
30
#

3.如果是交互式程序，让用户输入时最好给出一点提示：

# read -p "input your name and age, split with space: " yourname yourage
input your name and age, split with space: Tom 31
# echo $yourname
Tom
# echo $yourage
31
#

?

4.如果输入的行按照分隔符来分割后字段数大于指定的变量数，则多出来的字段全部赋值给最后一个变量

# read -p "input your name and age, split with space: " yourname yourage
input your name and age, split with space: James 39 Lakers
# echo $yourname
James
# echo $yourage
39 Lakers
#

5.如果提示用户输入密码之类的内容，就不宜将其显示在控制台，-s选项可以用在这种场景下

# read -p "input your password: " password
input your password: 123456
# echo "your password is: $password"
your password is: 123456
#

# read -s -p "input your password: " password
input your password: #?
# echo "your password is: $password" ? ? ? ??
your password is: 951753
#

可以看到，输入的密码没有显示出来

6.默认遇到换行符read命令返回，可以限制读入的总字符数，当输入的总字符数达到后read立即返回，

# read -p "input your firstname and lastename, split with space: " firstname lastname?
input your firstname and lastename, split with space: Allen LongestLastNameEver
# echo $firstname
Allen
# echo $lastname
LongestLastNameEver
#

-n 选项可以用于指定读入的字符数

# read -p "input your firstname and lastename, split with space: " -n 10 firstname lastname?
input your firstname and lastename, split with space: abcde abcd]#
# echo $firstname
abcde
# echo $lastname
abcd
#

7. 指定结束符，默认遇到换行符结束读取，read返回，通过-d可以指定新的结束符

# read -d "$" -p "input your name and age,split with spaceand stop with $ :" name age ?
input your name and age,split with spaceand stop with $ :Smart 25$ #?
# echo $name
Smart
# echo $age
25
#?

8. 使用其他字符作为分隔符

# IFS=";"
# read ?-p "input your name and age,split with semicolon(;) :" name age
input your name and age,split with semicolon(;) :Smart;23
# echo $name?
Smart
# echo $age
23
#?

9.禁止转义，-r

# read ?-p "input your name and age,split with space :" name age
input your name and age,split with space :"Han\"" 30
# echo $name
"Han""
# echo $age
30
#

# read -r -p "input your name and age,split with space :" name age
input your name and age,split with space :"Ham\"" 51
# echo $name
"Ham\""
# echo $age
51
#

10.将数据读入数组

# read -p "input 3 numbers, split with space: " -a myarray ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
input 3 numbers, split with space: 12 13 34
# echo "the first is ${myarray[0]}, the second is ${myarray[1]}, the third is ${myarray[2]}"
the first is 12, the second is 13, the third is 34
#?

11.使用默认值

read -e -i "Dav 25" -p "input your name and age,split with space :" name age
input your name and age,split with space :Dav 25
# echo $name
Dav
# echo $age
25

12.从字符串读取

#str="Tompthon 67"
#read name age <<< $str
#echo $name
Tompthon
#echo $age
67
#

?