#!/bin/bash

#使用date精确延时的函数，参数是毫秒
function precise_sleep_ms() {
    local duration_ms=$1

    # 将毫秒转换为秒
    local duration_sec=$(echo "scale=9; $duration_ms / 1000" | bc)
	duration_sec=$(printf "%.3f" "$duration_sec")
    # 计算结束时间点
    local end_time=$(echo "$(date +%s.%N) + $duration_sec" | bc)

    while [[ $(date +%s.%N) < $end_time ]]; do
        sleep 0.000001  # 使用更短暂的sleep减少CPU占用
    done
}
#使用date来获取到毫秒级别
function get_millisecond() {
	date +%Y-%m-%d' '%H:%M:%S.%N | cut -b 1-23
}

#延时length毫秒
function mt_sleep_ms() {
	local length=$1
	#延时$length毫秒
	if ! date +%N | grep -q '[0-9]\{9\}'; then
		#有些系统上的date命令可能不支持%N（纳秒），则使用不精确的sleep函数
		echo "Error: Your system's 'date' command does not support nanoseconds, use sleep cmd."
		sleep $length/1000
    else
		precise_sleep_ms $length
	fi
}
echo "test 5ms"
get_millisecond
mt_sleep_ms 5
get_millisecond
echo -e "\n"

echo "test 10ms"
get_millisecond
mt_sleep_ms 10
get_millisecond
echo -e "\n"

echo "test 100ms"
get_millisecond
mt_sleep_ms 100
get_millisecond
echo -e "\n"

echo "test 1000ms"
get_millisecond
mt_sleep_ms 1000
get_millisecond
echo -e "\n"

echo "test 5000ms"
get_millisecond
mt_sleep_ms 5000
get_millisecond
echo -e "\n"

echo "test 10000ms"
get_millisecond
mt_sleep_ms 10000
get_millisecond

运行结果如下，可以看出，5ms和10ms都不是特别准确，100ms完后准确点