bash 如何将文件逐行传送到多个读取变量中？
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How do I pipe a file line by line into multiple read variables?
提问by mlebel
I have a file that contains information in two columns:
我有一个包含两列信息的文件：
box1 a1
box2 a2
I'm trying to read this file line by line into readand have each line items be put into a variable.
我正在尝试逐行读取此文件，read并将每个行项目放入一个变量中。
On the first pass, $awould contain box1and $bwould contain a1.
在第一遍时，$a将包含box1并且$b将包含a1。
On the second pass, $awould contain box2and $bwould contain a2, etc.
在第二遍，$a将包含box2和$b将包含a2等。
An example of the code that I am using to try to achieve is this:
我用来尝试实现的代码示例如下：
for i in text.txt; do
while read line; do
echo $line | read a b;
done < text.txt;
echo $a $b;
done
This gives me the following results:
这给了我以下结果：
box1 a1 box2 a2
When I expected the following results:
当我预期以下结果时：
box1 a1
box2 a1
How can I fix this?
我怎样才能解决这个问题？
回答by chepner
Piping into a readcommand causes the variables to be set in a subshell, which makes them inaccessible (indeed, they are gone) to the rest of your code. In this case, though, you don't even need the forloop or the second readcommand:
管道到read命令会导致在子shell 中设置变量，这使得它们无法访问（实际上，它们已经消失）到您的其余代码中。但是，在这种情况下，您甚至不需要for循环或第二个read命令：
while read -r a b; do
echo "$a" "$b"
done < text.txt
