Set LastModified date of file

mrjj

Hi
QFileInfo seems only to allow reading it
http://doc.qt.io/qt-5/qfileinfo.html#lastModified

so utime could be used on win/linux
https://msdn.microsoft.com/en-us/library/4wacf567(v=vs.140).aspx
https://linux.die.net/man/2/utime

or if only win
https://msdn.microsoft.com/en-us/library/ms724933(VS.85).aspx

? Offline

Hi!
I think the following behaves pretty much like touch (changes the last modified date, creates the file if it didn't exist before):

bool touch(const QString& filePath)
{
    QFile file(filePath);
    if (!file.open(QIODevice::ReadWrite)) {
        return false;
    }
    const quint64 size = file.size();
    file.seek(size);
    file.write( QByteArray(1, '0') );
    file.resize(size);
    return true;
}

samdol

@mrjj
I tried as following,

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/utime.h>
#include <time.h>

struct tm tma = {0}, tmm = {0};
struct _utimbuf ut;
tmm.tm_year = 102;
tmm.tm_mon = 1;
tmm.tm_mday = 15;
tmm.tm_hour = 10;
tmm.tm_min = 0;
tmm.tm_sec = 0;
ut.modtime = mktime(&tmm);


// Show file time before and after
if( _utime( "D:/kde/crt_utime.c", &ut ) == -1 )
   perror( "_utime failed\n" );
else
   printf( "File time modified\n" );
system( "dir D:\kde" );

The result is
Volume in drive D has no label.
Volume Serial Number is EA68-9A51

Directory of D:\kde

10/08/2016 02:51 PM <DIR> .
10/08/2016 02:51 PM <DIR> ..
02/15/2002 10:00 AM 0 crt_utime.c
1 File(s) 0 bytes
2 Dir(s) 151,142,400 bytes free

I can see the correctly chanaged time 10:00 AM. But when I check on my windows explorer, I can see the Date Modified is 9:00 AM. The time checked by system and explorer shows always 1 hour different result. I changed tmm.tm_isdst to positive, negative and zero, but still system and explorer show different time. Is my system infected by virus?

mrjj

Hi
I dont think you have a virus :)

You are right its related to the isdst / daylight savings.

http://stackoverflow.com/questions/12122084/confusing-behaviour-of-mktime-function-increasing-tm-hour-count-by-one

http://stackoverflow.com/questions/3660983/c-time-t-problem

But it seems you tried all values for it and it still have the 1 hour diff so you should try some of the suggestion from the links.
Some seems to do
setenv("TZ", "", 1);
tzset();
before mktime to correct it.

benlau

@samdol In fact, you may just pass a null pointer to the second argument of utime. Then it will be set to current time.

That is how I implement touch():

https://github.com/benlau/qtshell/blob/master/qtshell.cpp#L178

? Offline

@benlau QtShell looks nice, thanks for sharing!

Jeronimo

@benlau why you do this change? path.toLocal8Bit().constData()

benlau

@Jeronimo Convert QString to const char*.

p.s Just updated the source to use toUtf8() instead of toLocal8Bit().

samdol

@mrjj

In fact my computer adjust clock for Daylight saving time.
So I did,
Control Panel --> Time Zone Settings
--> Uncheck Automatically adjust clock for Daylight Saving Time.

Now the lastmodified time on system and explorer are the same.
Thank you.

samdol

@benlau
Hi Benla,
I tested the touch function in qtshell.cpp.

bool QtShell::touch(const QString &path)
{
...
QByteArray bytes = path.toUtf8();

    if (utime(bytes.constData(), 0) == -1) {
        qWarning() << "utimes failed:" << path;

res = false;
...
}

It works fine for english filename. But if the filename contains some chinese
charactors then it gives an error and I could not modified time stamp of file.
I am using Windows 7. Thank you.

benlau

@samdol Hi, I just setup a Windows 10 to test. Both of VC and Mingw works. Could you send me the failed file name?

samdol

@benlau
Here is a zip file containing two files. link text

The following is the code, I tested on my Windows7 English version.

bool res = true;
QFileInfo info(path);

if (!info.exists()) {

    QFile file(path);
    if (!file.open(QIODevice::WriteOnly)) {
        qWarning() << "Failed to create file:" << path;
        res = false;
    }
    file.close();

} else {
    QByteArray bytes = path.toUtf8();

    if (utime(bytes.constData(), 0) == -1) {
        qWarning() << "utimes failed:" << path;
        res = false;
    }
}

Guigas

Thank you for this, very simple, quick and it worked for me (tested only on windows so far)

dantti

Since Qt5.10 there is QFileDevice::setFileTime() https://doc.qt.io/qt-6/qfiledevice.html#setFileTime

SimonSchroeder

@samdol said in Set LastModified date of file:

It works fine for english filename. But if the filename contains some chinese
charactors then it gives an error

For future reference: By default char* on Windows uses the local 8 bit encoding (which means path.toLocal8Bit().constData() was correct and the local encoding on Linux is already UTF-8). In order to use toUtf8() on Windows you need to call setlocale(LC_ALL, ".UTF8") (preferrably once at the beginning of main). (If you also want to print UTF-8 characters to the console, you'll also need to set the UTF-8 codepage.)