Time Functions

The following functions are used with system time.

Function	Description
GetSystemTime	Retrieves the current system date and time in UTC format.
GetSystemTimeAdjustment	Determines whether the system is applying periodic time adjustments to its time-of-day clock.
GetTimeFormat	Formats a system time as a time string for a specified locale.
NtQuerySystemTime	Returns the system time.
RtlLocalTimeToSystemTime	Converts the specified local time to system time.
RtlTimeToSecondsSince1970	Converts the specified system time to the number of seconds since the first second of January 1, 1970.
SetSystemTime	Sets the current system time and date.
SetSystemTimeAdjustment	Enables or disables periodic time adjustments to the system’s time-of-day clock.
SystemTimeToFileTime	Converts a system time to a file time.
SystemTimeToTzSpecificLocalTime	Converts a UTC time to a specified time zone’s corresponding local time.
TzSpecificLocalTimeToSystemTime	Converts a local time to a UTC time.

The following functions are used with local time.

Function	Description
EnumDynamicTimeZoneInformation	Enumerates dynamic daylight saving time information entries stored in the registry.
FileTimeToLocalFileTime	Converts a UTC file time to a local file time.
GetDynamicTimeZoneInformation	Retrieves the current time zone and dynamic daylight saving time settings.
GetDynamicTimeZoneInformationEffectiveYears	Retrieves a range, expressed in years, for which a DYNAMIC_TIME_ZONE_INFORMATION has valid entries.
GetLocalTime	Retrieves the current local date and time.
GetTimeZoneInformation	Retrieves the current time zone settings.
GetTimeZoneInformationForYear	Retrieves the time zone settings for the specified year and time zone.
RtlLocalTimeToSystemTime	Converts the specified local time to system time.
SetDynamicTimeZoneInformation	Sets the current time zone and dynamic daylight saving time settings.
SetLocalTime	Sets the current local time and date.
SetTimeZoneInformation	Sets the current time zone settings.
SystemTimeToTzSpecificLocalTime	Converts a UTC time to a specified time zone’s corresponding local time.
SystemTimeToTzSpecificLocalTimeEx	Converts a UTC time with dynamic daylight saving time settings to a specified time zone’s corresponding local time.
TzSpecificLocalTimeToSystemTime	Converts a local time to a UTC time.
TzSpecificLocalTimeToSystemTimeEx	Converts a local time with dynamic daylight saving time settings to UTC time.

The following functions are used with file time.

Function	Description
CompareFileTime	Compares two file times.
FileTimeToLocalFileTime	Converts a UTC file time to a local file time.
FileTimeToSystemTime	Converts a file time to system time format.
GetFileTime	Retrieves the date and time that the specified file or directory was created, last accessed, and last modified.
GetSystemTimeAsFileTime	Retrieves the current system date and time in UTC format.
LocalFileTimeToFileTime	Converts a local file time to a file time based on UTC.
SetFileTime	Sets the date and time that the specified file or directory was created, last accessed, or last modified.
SystemTimeToFileTime	Converts a system time to a file time.

The following functions are used with MS-DOS date and time.

Function	Description
DosDateTimeToFileTime	Converts MS-DOS date and time values to a file time.
FileTimeToDosDateTime	Converts a file time to MS-DOS date and time values.

The following functions are used with Windows time.

Function	Description
GetSystemTimes	Retrieves system timing information.
GetTickCount	Retrieves the number of milliseconds that have elapsed since the system was started, up to 49.7 days.
GetTickCount64	Retrieves the number of milliseconds that have elapsed since the system was started.

The following functions are used with high-resolution performance counters.

Function	Description
QueryPerformanceCounter	Retrieves the current value of the high-resolution performance counter.
QueryPerformanceFrequency	Retrieves the frequency of the high-resolution performance counter.

The following functions are used with the auxiliary performance counter.

Function	Description
QueryAuxiliaryCounterFrequency	Queries the auxiliary counter frequency.
ConvertAuxiliaryCounterToPerformanceCounter	Converts the specified auxiliary counter value to the corresponding performance counter value; optionally provides the estimated conversion error in nanoseconds due to latencies and maximum possible drift.
ConvertPerformanceCounterToAuxiliaryCounter	Converts the specified performance counter value to the corresponding auxiliary counter value; optionally provides the estimated conversion error in nanoseconds due to latencies and maximum possible drift.

The following function is used with interrupt time.

tamy0612 / cpu_time.c

# include windows.h >

int main () <

int i= 0 ;

HANDLE hProcess = GetCurrentProcess ();

FILETIME ftCreation, ftExit, ftKernel, ftUser;

SYSTEMTIME stKernel;

SYSTEMTIME stUser;

GetProcessTimes (hProcess, &ftCreation, &ftExit, &ftKernel, &ftUser);

FileTimeToSystemTime (&ftKernel, &stKernel);

FileTimeToSystemTime (&ftUser, &stUser);

printf ( » \n Time in kernel mode = %u h %u m %u s %u ms » , stKernel. wHour ,stKernel. wMinute , stKernel. wSecond , stKernel. wMilliseconds );

printf ( » \n Time in user mode = %u h %u m %u s %u ms \n » , stUser. wHour ,stUser. wMinute , stUser. wSecond , stUser. wMilliseconds );

system ( » dir » );

GetProcessTimes (hProcess, &ftCreation, &ftExit, &ftKernel, &ftUser);

FileTimeToSystemTime (&ftKernel, &stKernel);

FileTimeToSystemTime (&ftUser, &stUser);

printf ( » \n Time in kernel mode = %u h %u m %u s %u ms » , stKernel. wHour ,stKernel. wMinute , stKernel. wSecond , stKernel. wMilliseconds );

printf ( » \n Time in user mode = %u h %u m %u s %u ms \n » , stUser. wHour ,stUser. wMinute , stUser. wSecond , stUser. wMilliseconds );

system ( » PAUSE » );

return 0 ;

>

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Computing CPU time in C++ on Windows

Is there any way in C++ to calculate how long does it take to run a given program or routine in CPU time?

I work with Visual Studio 2008 running on Windows 7.

5 Answers 5

If you want to know the total amount of CPU time used by a process, neither clock nor rdtsc (either directly or via a compiler intrinsic) is really the best choice, at least IMO. If you need the code to be portable, about the best you can do is use clock , test with the system as quiescent as possible, and hope for the best (but if you do, be aware that the resolution of clock is CLOCKS_PER_SEC , which may or may not be 1000, and even if it is, your actual timing resolution often won’t be that good — it may give you times in milliseconds, but at least normally advance tens of milliseconds at a time).

Since, however, you don’t seem to mind the code being specific to Windows, you can do quite a bit better. At least if my understanding of what you’re looking for is correctly, what you really want is probably GetProcessTimes , which will (separately) tell you both kernel-mode and user-mode CPU usage of the process (as well as the start time and exit time, from which you can compute wall time used, if you care). There’s also QueryProcessCycleTime , which will tell you the total number of CPU clock cycles used by the process (total of both user and kernel mode in all threads). Personally, I have a hard time imagining much use for the latter though — counting individual clock cycles can be useful for small sections of code subject to intensive optimization, but I’m less certain about how you’d apply it to a complete process. GetProcessTimes uses FILETIME structures, which support resolutions of 100 nanoseconds, but in reality most times you’ll see will be multiples of the scheduler’s time slice (which varies with the version of windows, but is on the order of milliseconds to tens of milliseconds).

How to get the system uptime in Windows? [closed]

Want to improve this question? Update the question so it’s on-topic for Stack Overflow.

Closed 8 years ago .

I am using windows 7 and xp. I want to know the uptime of the system.

What is the command / procedure for getting the uptime?

3 Answers 3

Following are eight ways to find the Uptime in Windows OS.

1: By using the Task Manager

In Windows Vista and Windows Server 2008, the Task Manager has been beefed up to show additional information about the system. One of these pieces of info is the server’s running time.

1. Right-click on the Taskbar, and click Task Manager. You can also click CTRL + SHIFT + ESC to get to the Task Manager.
2. In Task Manager, select the Performance tab.

The current system uptime is shown under System or Performance ⇒ CPU for Win 8/10.

2: By using the System Information Utility

The systeminfo command line utility checks and displays various system statistics such as installation date, installed hotfixes and more. Open a Command Prompt and type the following command:

You can also narrow down the results to just the line you need:

3: By using the Uptime Utility

Microsoft have published a tool called Uptime.exe. It is a simple command line tool that analyses the computer’s reliability and availability information. It can work locally or remotely. In its simple form, the tool will display the current system uptime. An advanced option allows you to access more detailed information such as shutdown, reboots, operating system crashes, and Service Pack installation.

Read the following KB for more info and for the download links:

To use it, follow these steps:

1. Download uptime.exe from the above link, and save it to a folder, preferably in one that’s in the system’s path (such as SYSTEM32).
2. Open an elevated Command Prompt window. To open an elevated Command Prompt, click Start, click All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator. You can also type CMD in the search box of the Start menu, and when you see the Command Prompt icon click on it to select it, hold CTRL + SHIFT and press ENTER .
3. Navigate to where you’ve placed the uptime.exe utility.
4. Run the uptime.exe utility. You can add a /? to the command in order to get more options.

It does not offer many command line parameters:

3.1: By using the old Uptime Utility

There is an older version of the «uptime.exe» utility. This has the advantage of NOT needing .NET. (It also has a lot more features beyond simple uptime.)

4: By using the NET STATISTICS Utility

Another easy method, if you can remember it, is to use the approximate information found in the statistics displayed by the NET STATISTICS command. Open a Command Prompt and type the following command:

The statistics should tell you how long it’s been running, although in some cases this information is not as accurate as other methods.

5: By Using the Event Viewer

Probably the most accurate of them all, but it does require some clicking. It does not display an exact day or hour count since the last reboot, but it will display important information regarding why the computer was rebooted and when it did so. We need to look at Event ID 6005, which is an event that tells us that the computer has just finished booting, but you should be aware of the fact that there are virtually hundreds if not thousands of other event types that you could potentially learn from.

Note: BTW, the 6006 Event ID is what tells us when the server has gone down, so if there’s much time difference between the 6006 and 6005 events, the server was down for a long time.

Note: You can also open the Event Viewer by typing eventvwr.msc in the Run command, and you might as well use the shortcut found in the Administrative tools folder.

1. Click on Event Viewer (Local) in the left navigation pane.
2. In the middle pane, click on the Information event type, and scroll down till you see Event ID 6005. Double-click the 6005 Event ID, or right-click it and select View All Instances of This Event.
3. A list of all instances of the 6005 Event ID will be displayed. You can examine this list, look at the dates and times of each reboot event, and so on.
4. Open Server Manager tool by right-clicking the Computer icon on the start menu (or on the Desktop if you have it enabled) and select Manage. Navigate to the Event Viewer.

5.1: Eventlog via PowerShell

6: Programmatically, by using GetTickCount64

GetTickCount64 retrieves the number of milliseconds that have elapsed since the system was started.

7: By using WMI

8: The new uptime.exe for Windows XP and up

Like the tool from Microsoft, but compatible with all operating systems up to and including Windows 10 and Windows Server 2016, this uptime utility does not require an elevated command prompt and offers an option to show the uptime in both DD:HH:MM:SS and in human-readable formats (when executed with the -h command-line parameter).