how to change the RTC date and time in c++?

Ramkumar Mohan

JonB

@Ramkumar-Mohan
This depends on the OS, regardless of C++ or Qt.

Ramkumar Mohan

@JonB ok, but how to set the RTC date and time in (Linux OS) programmatically?

mpergand

@Ramkumar-Mohan
You need to execute some commands with QProcess.
see: https://www.systutorials.com/docs/linux/man/8-clock/

candy76041820

@mpergand Or, if you prefer the hard way, call clock_settime(). Maybe you need to sudo.

mpergand

@candy76041820 said in how to change the RTC date and time in c++?:

Maybe you need to sudo.

I wouldn't be surprised if that was the case..

JonB

@candy76041820 said in how to change the RTC date and time in c++?:

@mpergand Or, if you prefer the hard way, call clock_settime(). Maybe you need to sudo.

closk_settime(): https://stackoverflow.com/a/66894317/489865

It is also possible that OP's " RTC date and time " might require using Linux hwclock, q.v..

OP will certainly need some kind of su privilege!

Ramkumar Mohan

@mpergand

QString string = ui->dateTime->date(). toString(""yyyy-MM-dd hh: mm");
QString dateTimeString ("date-s");
dateTimeString.append(string);
int systemDateTimeStatus = system(dateTimeString.toStdString().c_str());
if (systemDateTimeStatus ==-1)
{
qDebug() "Failed to change date time";
}
int systemHwClockStatus = system("sudo hwclock-w");
if (systemHwClockStatus == -1),
{
qDebug() "Failed to sync hardware clock";
}

I wrote this code but it doesn't work properly. It shows the error below,

ERROR ::

date: invalid date ‘2022-08-26 hh:mm’
256

Any ideas on how to solve it?

jsulm · date: invalid date ‘2022-08-26 hh:mm’ 256

@Ramkumar-Mohan said in how to change the RTC date and time in c++?:

QString string = ui->dateTime->date(). toString(""yyyy-MM-dd hh: mm");

Why do you call date() here? Date does not contain time.

QString string = ui->dateTime->toString(""yyyy-MM-dd hh: mm");

mchinand

@Ramkumar-Mohan said in how to change the RTC date and time in c++?:

QString string = ui->dateTime->date(). toString(""yyyy-MM-dd hh: mm");

You are extracting the date from your QDateTime before converting it to a string, so you no longer have the time. Use QDateTime::toString() instead

Ramkumar Mohan

@jsulm

https://developer.toradex.com/linux-bsp/how-to/linux-features/real-time-clock-rtc-linux/

To set system time, use the date command:

date -s "2013-11-19 15:11:40"

Setting the system time using the date command does not automatically synchronize the RTCs. Use the hwclock command after entering the date command to synchronize an RTC with the updated system time:

hwclock -w

I did as per above link.

I'm not sure if this is the correct way or not .

mchinand

@Ramkumar-Mohan said in how to change the RTC date and time in c++?:

date: invalid date ‘2022-08-26 hh:mm’

The error and @jsulm and my replies are telling you what is wrong, you formed the string you are using to set the time incorrectly. Your string has 'hh:mm' at the end because those have no special meaning when formatting a QDate, which you are doing.

Ramkumar Mohan

@Ramkumar-Mohan

QProcess Dateprocess (this);
Dateprocess.start("sh",QStringList()<<"-c"<<"sudo timedatectl set-timezone Asia/Kolkata");
if (!Dateprocess.waitForStarted())
{
qDebug() << "Error : " << Dateprocess.errorString();
}
Dateprocess.waitForFinished(-1);

QDate curdate=QDate::currentDate();
QString datetxt= curdate.toString("yyyy / MM / dd");
ui->SysDate_Lbl->setText(datetxt);

int systemHwClockStatus = system("sudo hwclock -w");
if (systemHwClockStatus == -1 )
{
   qDebug() << "Failed to sync hardware clock";

}

I have written another code. Check if this code works. How to do? I don't know

mchinand

Did you try fixing your dateTime string in your original code?

Ramkumar Mohan · date: invalid date ‘2022-08-26 hh:mm’

@mchinand

QProcess Dateprocess (this);
Dateprocess.start("sh",QStringList()<<"-c"<<"sudo timedatectl set-timezone Asia/Kolkata");
if (!Dateprocess.waitForStarted())
{
qDebug() << "Error : " << Dateprocess.errorString();
}
Dateprocess.waitForFinished(-1);

QDate curdate=QDate::currentDate();
QString datetxt= curdate.toString("yyyy / MM / dd");
ui->SysDate_Lbl->setText(datetxt);

int systemHwClockStatus = system("sudo hwclock -w");
if (systemHwClockStatus == -1 )
{
   qDebug() << "Failed to sync hardware clock";
}
system("sudo timedatectl set-local-rtc 1");

In this code, I have written using the shell command. and set the time to RTC using the last line in it.

system("sudo timedatectl set-local-rtc 1");

I checked with the timedatectl command in the Linux terminal, it shows a warning message.

tells to set UTC time to RTC. I want to reset the RTC time if it changes. Is this way correct?

If I do RTC reset, I want to set the Date and time in a label, if I do this I will get which time update. UTC time or local time . I don't know that. tell me if you know.

Thank you.

jsulm

@Ramkumar-Mohan Did you actually read what I wrote?! And also the error message you get?
Again: you're trying to set "2022-08-26 hh:mm" as datetime: do you think this is valid datetime?
I told you what to change: did you try?