读取用户输入标准输入时，文件已经重定向到标准输入 [英] Read stdin for user input when a file is already redirected to stdin

问题描述

所以我试图做类似如下：

So I'm trying to do something like the following:

while read line; do
    read userInput
    echo "$line $userInput"
done < file.txt

所以说，file.txt的有：

So say file.txt has:

Hello?
Goodbye!

运行程序会创建：

Running the program would create:

Hello?
James
Hello? James
Goodbye!
Farewell
Goodbye! Farewell

问题（自然）变成了userinput从标准输入读取这对我们来说是file.txt的读取。有没有办法改变它的暂时从阅读到终端为了抢夺用户输入？

The issue (naturally) becomes that the userinput read reads from stdin which in our case is file.txt. Is there a way to change where it's reading from temporarily to the terminal in order to grab user input?

请注意：我一起工作的文件，20万行代码。每行约500个字符长。如果需要，所以记住这一点。

Note: The file I am working with is 200,000 lines long. and each line is about 500 chars long. So keep that in mind if needed

推荐答案

而不是使用重定向，可以打开 file.txt的来文件描述符（例如3）并使用阅读-u 3 从文件而不是从读标准输入：

Instead of using redirection, you can open file.txt to a file descriptor (for example 3) and use read -u 3 to read from the file instead of from stdin:

exec 3<file.txt
while read -u 3 line; do
    echo $line
    read userInput
    echo "$line $userInput"
done

另外，通过Jaypal辛格的建议，这可以写为：

Alternatively, as suggested by Jaypal Singh, this can be written as:

while read line <&3; do
    echo $line
    read userInput
    echo "$line $userInput"
done 3<file.txt

这个版本的优点是，它也适用于 SH 为<$ C（即 -u 选项$ C>读不工作 SH ）。

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