[root@web ~]# { read -r LINE1; read -r LINE2; read -r LINE3; }
Some text here
[root@web ~]# echo $LINE2
with backslash \ here
[root@web ~]# echo $LINE3
dollar $HOME meet
[root@web ~]#
从Here Document读取
错误：read VAR <
EOF
正确：{ read VAR; } <
EOF
问题：为什么写在代码块中才能读取呢？
[root@web ~]# read VAR <
> EOF
[root@web ~]# echo "$VAR"
[root@web ~]# { read VAR; } <
> EOF
[root@web ~]# echo "$VAR"
hello
[root@web ~]#
从Here String读取
read VAR <<< "some string"
read VAR <<< "$STR"
[root@web ~]# read VAR <<< "some string"
[root@web ~]# echo $VAR
some string
[root@web ~]#
补充：关于 cat input.txt | read VAR 的问题
先说一下我对管道线的理解：管道线两侧的命令，前一个命令的输出（标准输出），将作为后一个命令的输入（标准输入）。两侧的命令都是在子进程中执行的，都有各自独立的地址空间，子进程会继承（复制）父进程所有的环境变量。子Shell（subshell）是一种特殊的子进程，它会继承（复制）父Shell的所有变量；对于非子Shell进程（外部命令），只有环境变量会被继承（复制）。但是，子进程一旦启动，它所有的变量只在它的进程空间中有效，它对变量的修改都是对自己范围之内的变量的修改，对父进程相同名称的变量是没有影响的。而子进程启动之后，它的父进程对父进程变量的修改，对子进程相同名称的变量也是没有影响的。
Advanced Bash-Scripting Guide: Chapter 3. Special Characters | 写道
|
pipe. Passes the output (stdout) of a previous command to the input (stdin) of the next one, or to the shell. This is a method of chaining commands together.
A pipe, as a classic method of interprocess communication, sends the stdout of one process to the stdin of another. In a typical case, a command, such as cat or echo, pipes a stream of data to a filter, a command that transforms its input for processing.
The output of a command or commands may be piped to a script.
A pipe runs as a child process, and therefore cannot alter script variables.
variable="initial_value"
echo "new_value" | read variable
echo "variable = $variable" # variable = initial_value
[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
上面的cat input.txt的输出将作为read VAR的输入。
[root@web ~]# cat input.txt | { read VAR; echo $VAR; }
Some text here
可以看到管道线后面的子Shell中确实读到了值。
[root@web ~]# echo $VAR
但父Shell中的相同变量不会改变。
[root@web ~]#
作者“Bash @ Linux”