在 while 读取循环内读取密钥失败

Question

这是我检测按键按下的脚本：

#!/bin/bash
echo "Reading keys."
while [ "x$keypress" = "x" ]; do
  read -n 1 -t 1 -s keypress
  printf "."
done
printf "\n"
echo "Pressed key: "$keypress

这似乎工作正常（例如在一段时间后按“q”键）：

$ ./InputKey.sh
Reading keys.
.............................................
Pressed key: q

但是，如果我将它放在一个循环中，该循环会读取我的File.txt 并等待每一行的键：

#!/bin/bash
MyList=File.txt
while IFS=, read -ra ListLine
do
    echo "Processing line: "$ListLine
    echo "Press [S] to count as Secret or [P] to count as Public."
  while [ "x$keypress" = "x" ]; do
        read -n 1 -t 1 -s keypress
    printf "."
    done
    printf "\n"
    echo "Pressed key: "$keypress
done < "$MyList"

程序根本不等待按键，这是奇怪的结果：

$ ./prueba07.sh
Processing line: d:\Temp
Press [S] to count as Secret or [P] to count as Public.
.
Pressed key: c
Processing line: :\Temp
Press [S] to count as Secret or [P] to count as Public.

Pressed key: c
Processing line: e:\Temp
Press [S] to count as Secret or [P] to count as Public.

Pressed key: c
Processing line:
Press [S] to count as Secret or [P] to count as Public.

Pressed key: c

这是File.txt的内容：

d:\Temp
c:\Temp
e:\Temp 

我在某处读到问题来自 <"$MyList" 重定向器，它消耗了所有 stdin。

所以，我找到了this thread 并添加了&3 重定向器：

#!/bin/bash
MyList=File.txt
while IFS=, read -ra ListLine <&3
do
    echo "Processing line: "$ListLine
    echo "Press [S] to count as Secret or [P] to count as Public."
  while [ "x$keypress" = "x" ]; do
        read -n 1 -t 1 -s keypress
    printf "."
    done
    printf "\n"
    echo "Pressed key: "$keypress
done 3< "$MyList"

现在程序等待一键按下。但其余部分会自动重复（例如仅按一次 p 时）：

$ ./prueba07.sh
Processing line: d:\Temp
Press [S] to count as Secret or [P] to count as Public.
..
Pressed key: p
Processing line: c:\Temp
Press [S] to count as Secret or [P] to count as Public.

Pressed key: p
Processing line: e:\Temp
Press [S] to count as Secret or [P] to count as Public.

Pressed key: p
Processing line:
Press [S] to count as Secret or [P] to count as Public.

Pressed key: p

这样的问题怎么解决？ 谢谢你。

EDIT-01：针对读取关键行测试了此更改，但没有结果：

read -n 1 -t 1 -s keypress </dev/tty

从this other 线程中提取。

EDIT-02：在 Ubuntu Desktop v12 和 CygWin (Windows 7) 上测试。

EDIT-03：下面的答案是正确的。我为脚本选择的最后一个更改是（最后只有一行）：

#!/bin/bash
MyList=File.txt
while IFS=, read -ra ListLine <&3
do
    echo "Processing line: "$ListLine
    echo "Press [S] to count as Secret or [P] to count as Public."
  while [ "x$keypress" = "x" ]; do
        read -n 1 -t 1 -s keypress
    printf "."
    done
    printf "\n"
    echo "Pressed key: "$keypress
    unset keypress
done 3< "$MyList"

Answer 1

您可以从不同的文件描述符中读取，并重构内部循环

while IFS=, read -r -u 3 -a ListLine
do
  echo 'Processing line:' "$ListLine"
  echo 'Press [S] to count as Secret or [P] to count as Public.'
  until read -n 1 -t 1 -s keypress
  do
    printf .
  done
  echo
  echo 'Pressed key:' $keypress
done 3< File.txt

Does bash support doing a read nested within a read loop?

Answer 2

它在第一个循环之后工作，因为 keypress 是空的，但在随后的调用中，keypress 仍然设置为第一次通过循环时设置的值。 您只需要将 keypress 变量设置为空字符串。