更新历史记录：

• 答案的第一部分实现了可暂停的倒计时（打印很多行）
• 在第二部分中实现了一个不那么冗长的Pausable命令行（在按键时打印一个静态行+额外的消息）
• 第三个代码片段中有一个更复杂的可暂停的倒计时，它会不断更新同一行。
  可暂停倒计时

结合一些类似问题here的提示和一些关于如何读取单个字符(e.g. here, otherwise everywhere on the internet)的外部资源，并添加一个额外的循环用于恢复，这就是我的想法：

#!/bin/bash

# Starts a pausable/resumable countdown.
# 
# Starts the countdown that runs for the
# specified number of seconds. The 
# countdown can be paused and resumed by pressing the
# spacebar. 
#
# The countdown can be sped up by holding down any button
# that is no the space bar.
#
# Expects the number of seconds as single
# argument.
#
# @param $1 number of seconds for the countdown
function resumableCountdown() {
  local totalSeconds=$1
  while (( $totalSeconds > 0 ))
  do
    IFS= read -n1 -t 1 -p "Countdown $totalSeconds seconds (press <Space> to pause)" userKey
    echo ""
    if [ "$userKey" == " " ]
    then
      userKey=not_space
      while [ "$userKey" != " " ]
      do
        IFS= read -n1 -p "Paused, $totalSeconds seconds left (press <Space> to resume)" userKey
    echo ""
      done
    elif  [ -n "$userKey" ]
    then
      echo "You pressed '$userKey', press <Space> to pause!"
    fi
    totalSeconds=$((totalSeconds - 1))
  done
}

# little test
resumableCountdown 60

这可以保存并作为独立脚本运行。该功能可以在其他地方重复使用。它用SPACE暂停/恢复，因为这对我来说似乎更直观，因为它是如何工作的。嵌入在浏览器中的视频播放器。
倒计时也可以通过按空格键以外的键来加速（这是一个功能）。

发出警告消息并等待可暂停超时

以下变体实现了一个 pausable timeout，它只打印初始警告消息，除非用户通过按空格键暂停或恢复（内部）倒计时：

# Prints a warning and then waits for a
# timeout. The timeout is pausable.
#
# If the user presses the spacebar, the 
# internal countdown for the timeout is 
# paused. It can be resumed by pressing
# spacebar once again.
#
# @param $1 timeout in seconds
# @param $2 warning message
warningWithPausableTimeout() {
  local remainingSeconds="$1"
  local warningMessage="$2"
  echo -n "$warningMessage $remainingSeconds seconds (Press <SPACE> to pause)"
  while (( "$remainingSeconds" > 0 ))
  do
    readStartSeconds="$SECONDS"
    pressedKey=""
    IFS= read -n1 -t "$remainingSeconds" pressedKey
    nowSeconds="$SECONDS"
    readSeconds=$(( nowSeconds - readStartSeconds ))
    remainingSeconds=$(( remainingSeconds - readSeconds ))
    if [ "$pressedKey" == " " ]
    then
      echo ""
      echo -n "Paused ($remainingSeconds seconds remaining, press <SPACE> to resume)"
      pressedKey=""
      while [ "$pressedKey" != " " ]
      do
        IFS= read -n1 pressedKey
      done
      echo ""
      echo "Resumed"
    fi
  done
  echo ""
}

warningWithPausableTimeout 10 "Program will end in"
echo "end."

可暂停倒计时，更新同一行

这是一个类似于第一个倒计时，但它只需要一行。依靠echo -e擦除和覆盖以前打印的消息。

# A pausable countdown that repeatedly updates the same line.
#
# Repeatedly prints the message, the remaining time, and the state of
# the countdown, overriding the previously printed messages.
#
# @param $1 number of seconds for the countdown
# @param $2 message
singleLinePausableCountdown() {
  local remainingSeconds="$1"
  local message="$2"
  local state="run"
  local stateMessage=""
  local pressedKey=""
  while (( $remainingSeconds > 0 ))
  do
    if [ "$state" == "run" ]
    then
      stateMessage="[$remainingSeconds sec] Running, press <SPACE> to pause"
    else
      stateMessage="[$remainingSeconds sec] Paused, press <SPACE> to continue"
    fi
    echo -n "$message $stateMessage"
    pressedKey=""
    if [ "$state" == "run" ]
    then 
      IFS= read -n1 -t 1 pressedKey
      if [ "$pressedKey" == " " ]
      then
        state="pause"
      else 
        remainingSeconds=$(( remainingSeconds - 1 ))
      fi
    else
      IFS= read -n1 pressedKey
      if [ "$pressedKey" == " " ]
      then
        state="run"
      fi
    fi
    echo -ne "\033[1K\r"
  done
  echo "$message [Done]"
}

如果线条比控制台宽度长，这个命令可能会表现得很奇怪（它不会完全擦除线条）。
未分类的收集提示的任何人谁试图使某事。相似：

• IFS= read -n1读取单个字符
• read -t <seconds>为read设置超时。一旦超时过期，read将以非零值退出，并将变量设置为空。
• Magic bash内置变量$SECONDS以秒为单位测量从脚本开始的时间。
• 如果一条线已经用echo -n打印，那么它可以用echo -ne "\033[1K\r"擦除和重置。