在 Linux 中使用 C++ 设置系统日期和时间

Question

我正在开发一个将系统日期和时间更改为指定值的跨平台应用程序。我已经完成 Windows 的部分。

如何从 Linux 中的 C++ 程序设置系统日期和时间？我正在寻找类似于 SetSystemTime(SYSTEMTIME &x).

的函数

据我了解 settimeofday() 对日期没有任何作用，我不确定函数 stime() 的用法。我希望mktime()与我的需求无关。

谁能帮帮我。

Answer 1

你理解错了。 settimeofday(2) is setting the Epoch time. which is both date and time. Read time(7)

因此，如果您从表示日期的字符串开始，请使用 strptime(3) to a struct tm then convert that to a Unix time with mktime(3) 转换该字符串，然后将其提供给 settimeofday（即 tv_sec 字段）。

然而，settimeofday 需要 root 权限，我相信你通常应该避免调用它（至少在平时，Internet-connected, computers). Better set some NTP client service on your Linux PC (e.g. run ntpd or chrony and more generally read the sysadmin chapter on keeping time...). See also adjtimex(2)

顺便说一句，在 multi-tasking system -like Linux or Windows- is a very dangerous operation (since it will upset and disturb a lot of system tasks depending or using the time). There are few good reasons to do that (it is a very bad idea in general). If you do that, do that with very few programs & services running (e.g. single user mode Linux 上突然更改系统时间）。你不应该在普通的应用程序代码中这样做。

Answer 2

我写这段代码是为了在Linux下设置日期和时间。

#include <time.h>

struct tm time = { 0 };

time.tm_year = Year - 1900;
time.tm_mon  = Month - 1;
time.tm_mday = Day;
time.tm_hour = Hour;
time.tm_min  = Minute;
time.tm_sec  = Second;

if (time.tm_year < 0)
{
    time.tm_year = 0;
}

time_t t = mktime(&time);

if (t != (time_t) -1)
{
    stime(&t);
}

请注意 stime 需要 root 权限。

Answer 3

使用 clock_settime 而不是 stime 的示例，因为 pointed out, stime is now deprecated. I like the reference code from Converting between timespec & std::chrono 为此：

#include <time.h>
#include <chrono>

using std::chrono; // for example brevity

constexpr timespec timepointToTimespec(
    time_point<system_clock, nanoseconds> tp)
{
    auto secs = time_point_cast<seconds>(tp);
    auto ns = time_point_cast<nanoseconds>(tp) -
             time_point_cast<nanoseconds>(secs);

    return timespec{secs.time_since_epoch().count(), ns.count()};
}

const char* timePointToChar(
    const time_point<system_clock, nanoseconds>& tp) {
    time_t ttp = system_clock::to_time_t(tp);
    return ctime(&ttp);
}

const time_point system_time = system_clock::now();
cout << "System time = " << timePointToChar(system_time) << endl;

const timespec ts = timepointToTimespec(system_time);
clock_settime(CLOCK_REALTIME, &ts);

在 Linux 中使用 C++ 设置系统日期和时间

Set System date and time using C++ in Linux

c++

linux

datetime