QT -- qfileinfo file information reading

QFileInfo File information read

QFileInfo Class can read important file information

1、 Returns the suffix of the file

2、 Return the file name , Exclude path

3、 Return file path , Do not include filename

4、 Return the filename , Including paths （ It can be an absolute path or a relative path ）

Use QFileInfo Class needs to contain header files #include <QFileInfo>

The code is as follows ：

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>
#include <QDebug>
#include <QFileInfo>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    
    ui->setupUi(this);
    // Hit the new button , A file dialog box pops up 
    connect(ui->pushButton,&QPushButton::released,[=](){
    
        // File dialog  --  Return the file path of the selected file 
        QString path = QFileDialog::getOpenFileName(this," Select file ","/home/chantui/work/resourceFile","Images (*.png *.xpm *.jpg);;Text files (*.txt);;XML files (*.xml)");

        // Use file information class QFileInfo
        // Incoming file path 
        QFileInfo fileinfo(path);
        //1、 The suffix of the output file 
        qDebug()<<" The suffix of the file ："<<fileinfo.suffix();
        //2、 Return the file name , Exclude path 
        qDebug()<<" File name , Exclude path ："<<fileinfo.fileName();
        //3、 Return file path , Do not include filename 
        qDebug()<<" File path , Do not include filename ："<<fileinfo.path();
        //4、 Return the filename , Including paths （ It can be an absolute path or a relative path ）
        qDebug()<<" file name , Including paths （ It can be an absolute path or a relative path ）："<<fileinfo.filePath();
    });
}

MainWindow::~MainWindow()
{
    
    delete ui;
}

The operation results are as follows ：

5、 Return file size

6、 Returns the file creation time 、 Last modified time .

File creation time ：birthTime() （Windows Available under the system ,Linux Not available under the system ）

Last modified time of file ：lastModified()

We need to pay attention to , When you need to return the relevant time information of the file , You need to pay attention to the return value . You also need to include the header file #include <QDateTime>

When used directly qDebug() To output ,

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>
#include <QDebug>
#include <QFileInfo>
#include <QDateTime>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    
    ui->setupUi(this);
    // Hit the new button , A file dialog box pops up 
    connect(ui->pushButton,&QPushButton::released,[=](){
    
        // File dialog  --  Return the file path of the selected file 
        QString path = QFileDialog::getOpenFileName(this," Select file ","/home/chantui/work/resourceFile","Images (*.png *.xpm *.jpg);;Text files (*.txt);;XML files (*.xml)");

        // Use file information class QFileInfo
        // Incoming file path 
        QFileInfo fileinfo(path);
        //1、 Size of output file 
        qDebug()<<" Size of output file ："<<fileinfo.size();
        //2、 Return the creation date of the file 
        qDebug()<<" Date the file was created ："<<fileinfo.birthTime();
        //3、 Returns the last modified date of the file 
        qDebug()<<" Date of last modification of the document ："<<fileinfo.lastModified();
    });
}

MainWindow::~MainWindow()
{
    
    delete ui;
}

The output is as follows ：

I don't know why , The printed creation date is invalid .

If I want to output in the date format I specify , So how do you do that ？ View help documents , We can use toString() This function .

How to set the format ？ Look below


The code is as follows ,

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>
#include <QDebug>
#include <QFileInfo>
#include <QDateTime>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    
    ui->setupUi(this);
    // Hit the new button , A file dialog box pops up 
    connect(ui->pushButton,&QPushButton::released,[=](){
    
        // File dialog  --  Return the file path of the selected file 
        QString path = QFileDialog::getOpenFileName(this," Select file ","/home/chantui/work/resourceFile","Images (*.png *.xpm *.jpg);;Text files (*.txt);;XML files (*.xml)");

        // Use file information class QFileInfo
        // Incoming file path 
        QFileInfo fileinfo(path);
        //1、 Size of output file , Unit is byte 
        qDebug()<<" Size of output file , Unit is byte ："<<fileinfo.size();
        //2、 Return the creation date of the file 
        qDebug()<<" Date the file was created ："<<fileinfo.birthTime().toString("yyyy/MM/dd hh:mm:ss");
        //3、 Returns the last modified date of the file 
        qDebug()<<" Date of last modification of the document ："<<fileinfo.lastModified().toString("yyyy/MM/dd hh:mm:ss");
    });
}

MainWindow::~MainWindow()
{
    
    delete ui;
}

The operation results are as follows ：

stay ubuntu In the system , Using functions birthTime() To get the creation time of the file always returns invalid .

stay ubuntu In the system , Click on the file -> attribute , Nor can we find the creation time , You can only view the modification and access time .

Conclusion ：birthTime() stay Windows You can use , stay Linux In the system , The file has no information about the creation time ,（ Generally, there are only the latest modification time and the latest access time , Corresponding function respectively lastModified and lastRead ）

And it was said before ,created The function has been discarded , Don't use it in code . In future projects , When we're in Linux When you want to view information about file time in the system , Don't check its creation time , Only check its latest modification time and latest access time .