格式：read VAR
格式：read -p
[root@node56 ~]# read VAR
hello world
[root@node56 ~]# echo $VAR
hello world
[root@node56 ~]# read -p "Input your number: " VAR
Input your number: 123
[root@node56 ~]# echo $VAR
123
[root@node56 ~]# read VAR
yes\tno
[root@node56 ~]# echo $VAR
yestno
[root@node56 ~]#
读取一行文本，但是取消反斜杠的转义作用。
格式：read -r VAR
格式：read -p
man bash: read 写道
-r Backslash does not act as an escape character. The backslash is considered to be part of the
line. In particular, a backslash-newline pair may not be used as a line continuation.
[root@node56 ~]# read -r VAR
yes\tno
[root@node56 ~]# echo $VAR
yes\tno
[root@node56 ~]#
关于read -p
此参数用于在读取变量之前显示提示信息。如果输入重定向了，就不会显示，比如重定向从文件中读取。
也就是说，read -p PROMPT VAR 不等同于 echo PROMPT; read VAR 的组合。
man bash: read 写道
-p prompt
Display prompt on standard error, without a trailing newline, before attempting to read any
input. The prompt is displayed only if input is coming from a terminal.
读取密码（输入的字符不回显）
格式：read -s PASSWORD
格式：read -p
man bash: read 写道
-s Silent mode. If input is coming from a terminal, characters are not echoed.
[root@node56 ~]# echo $PASSWORD
[root@node56 ~]# read -s PASSWORD
[root@node56 ~]# echo $PASSWORD
12345
[root@node56 ~]# read -p "Input password: " -s PASSWORD
Input password:
[root@node56 ~]# echo $PASSWORD
54321
读取指定数量字符
格式：read -n
格式：read -p
man bash: read 写道
-n nchars
read returns after reading nchars characters rather than waiting for a complete line of input.
[root@node56 ~]# read -p "Input two chars: " -n 2 VAR
Input two chars: 12 [root@node56 ~]# echo $VAR
12
[root@node56 ~]#
在指定时间内读取
格式：read -t
格式：read -p
man bash: read 写道
-t timeout
Cause read to time out and return failure if a complete line of input is not read within timeout
seconds. This option has no effect if read is not reading input from the terminal or a pipe.
[root@node56 ~]# read -p "Input some words in 5 seconds: " -t 5 VAR
Input some words in 5 seconds: [root@node56 ~]#
从文件中读取
格式：read VAR
格式：read -r VAR
[root@web ~]# cat input.txt
Some text here
with backslash \ here
dollar $HOME meet
[root@web ~]# cat input.txt | read VAR
[root@web ~]# echo $VAR
[root@web ~]# read VAR
Some text here
[root@web ~]# read VAR1 VAR2 VAR3 VAR4
VAR1=Some VAR2=text VAR3=here VAR4=
[root@web ~]# read VAR1 VAR2
VAR1=Some VAR2=text here
[root@web ~]#
上面的直接对read命令输入重定向，只能读取输入文件中的一行。
如果需要读取整个文件，最好将其写在一个代码块中。
Advanced Bash-Scripting Guide: Chapter 3. Special Characters {} 写道
Block of code [curly brackets]. Also referred to as an inline group, this construct, in effect, creates an anonymous function (a function without a name). However, unlike in a "standard" function, the variables inside a code block remain visible to the remainder of the script.
The code block enclosed in braces may have I/O redirected to and from it.
Unlike a command group within (parentheses), as above, a code block enclosed by {braces} will not normally launch a subshell.
{ read LINE1; read LINE2; read LINE3; }
[root@web ~]# { read LINE1; read LINE2; read LINE3; }
Some text here
[root@web ~]# echo $LINE2
with backslash here
[root@web ~]# echo $LINE3
dollar $HOME meet
[root@web ~]#
上面LINE2中\ 没有读取出来，因为在没有加上-r参数时，read会转义。
现在加上-r参数来测试一下。
{ read -r LINE1; read -r LINE2;