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计时器的 bash 脚本

tag-icon • tag-icon command-line bash scripts time
计时器的 bash 脚本

我想编写一个 bash 脚本来运行一个 30 秒的计时器，30 秒后，它会在接下来的 30 秒内保持，然后该计时器会在接下来的 30 秒内启动并继续执行。

for ((i=30; i>0; i--)); do
   sleep 1 &
   print "$i \r"
   wait
done

使用上面的代码，我可以让计时器运行 30 秒，但我需要保持接下来的 30 秒，然后再次运行接下来的 30 秒的计时器。

我怎样才能做到这一点？

我可以用这个代码在 java 中做同样的事情

import java.util.Timer;
import java.util.TimerTask;
public class TestClass {
    static int count = 0;
    public static void main(String[] args)  {
        final TestClass test = new TestClass();
                Timer timer = new Timer();
                timer.schedule(new TimerTask() {
                    @Override
                    public void run() {
                        test.doStuff();
                      }
                }, 0, 1000);
    }
    public void doStuff() {
        if (count == 30) {
            try {
                Thread.sleep(30000);
                count = 0;
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println(++count);
    }
}

答案1

将循环包装成无限循环（IE一个while无条件的循环），并sleep 30在这个外层循环中添加一个。

while :
do
    ###  < your
    ###   timer
    ###   here >
    sleep 30
done

我建议您也删除该wait指令和&来自“ sleep 1 &”的。另外，print这不是写入终端的正确程序，请改用echo。

while :
do
    for ((i=30; i>0; i--))
    do
       sleep 1 
       echo -n "$i "
    done
    sleep 30
    echo ""
done

请注意，此计时器并不准确，因为评估循环指令需要花费（少量但不为零）时间。使用以下解决方案date会更好：例如，参见此处的倒计时函数：https://superuser.com/a/611582。

答案2

我认为你正在寻找这样的东西：

#!/bin/bash

## Infinite loop
while :; do
        ## Run a sleep command for 30 seconds in the background
        sleep 30 &
        ## $! is the PID of the last backgrounded process, so of the sleep.
        ## Wait for it to finish.
        c=30
        while [[ -e /proc/$! ]]; do
                printf '%s\r' "$(( --c ))"
                ## For more precision, comment the line below. This causes the
                ## script to wait for a second so it doesn't spam your CPU.
                ## If you need accuracy, comment the line out. Although, if you
                ## really need accuracy, don't use the shell for this.
                sleep 1
        done
done

或者，使用date：

#!/bin/bash
waitTime=30;
## Infinite loop
while :; do
        startTime=$(date +%s)
        currentTime=$(date +%s)
        c=$waitTime;
        while [[ $((currentTime - startTime)) -lt $waitTime ]]; do
                printf '%s\r' "$(( --c ))"  
                ## For more precision, comment the line below. This causes the
                ## script to wait for a second so it doesn't spam your CPU.
                ## If you need accuracy, comment the line out. Although, if you
                ## really need accuracy, don't use the shell for this.
                sleep 1
                currentTime=$(date +%s)
        done
        c=0
        echo "";
done

为了获得更高的精度，不要将日期存储在变量中：

#!/bin/bash
waitTime=4;
while :; do
        startTime=$(date +%s)
        c=$waitTime;
        while [[ $(($(date +%s) - startTime))  -lt $waitTime ]]; do
                printf '%s\r' "$(( --c ))"  
                sleep 1
        done
        c=0
done

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