shell脚本输入重定向古怪 [英] Shell scripting input redirection oddities

问题描述

任何人都可以解释这种现象？\r
运行：

Can anyone explain this behavior? Running:

#!/bin/sh
echo "hello world" | read var1 var2
echo $var1
echo $var2

\r
\r

结果没有被输出中，而

results in nothing being ouput, while:

#!/bin/sh
echo "hello world" > test.file
read var1 var2 < test.file
echo $var1
echo $var2

\r
\r

产生预期的输出结果：

produces the expected output:

hello
world

\r
\r

不应该管在一个步骤做什么重定向到TEST.FILE在第二个例子那样？我试图在同一code用破折号和Bash shell，并从他们两个人得到了相同的行为。

Shouldn't the pipe do in one step what the redirection to test.file did in the second example? I tried the same code with both the dash and bash shells and got the same behavior from both of them.

推荐答案

最近除了庆典是 lastpipe 选项，允许最后一个命令在管道在当前shell中运行，而不是一个子shell当作业控制被停用。

A recent addition to bash is the lastpipe option, which allows the last command in a pipeline to run in the current shell, not a subshell, when job control is deactivated.

#!/bin/bash
set +m      # Deactiveate job control
shopt -s lastpipe
echo "hello world" | read var1 var2
echo $var1
echo $var2

确实会输出

hello
world

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