Qt determines whether the folder path and file exist or not and creates them

Chapter1 Qt determines whether the folder path and file exist or not and creates them
- Qt determines whether a folder/directory exists
- Qt determines whether a file exists
Chapter2 Qt determines whether a file or folder exists and creates a folder
- 1. Determine whether the folder exists
- 2. Determine whether the file exists
- 3. Determine whether the file or folder exists (that is, it is not sure whether the string is a file or folder path)
- 4. Determine whether the folder exists, create it if it does not exist
- 5. The following is an excerpt of other network test codes

Chapter1 Qt determines whether the folder path and file exist or not and creates them

Original link: https://blog.csdn.net/yao_hou/article/details/121389476

Qt determines whether the folder/directory exists

Qt determines whether a folder/directory exists. You can use the exists method of the QDir class to determine. When using it, you need to include the header file #include , such as the following code:

#include <QCoreApplication>
#include <QDir>
#include <QDebug>

///
/// \brief determines whether the folder exists, and creates it if it does not exist.
/// \param fullPath
/// \return
///
bool DirExist(QString fullPath)
{<!-- -->
    QDir dir(fullPath);
    if(dir.exists())
    {<!-- -->
        //The current folder exists
        return true;
    }
    else
    {<!-- -->
        //Create if it does not exist
        bool ok = dir.mkdir(fullPath); //Only create a first-level subdirectory, that is, the upper-level directory must exist
        return ok;
    }
}

///
/// \brief determines whether the folder exists. If it does not exist, create it. Multi-level directories can be created.
/// \param fullPath
/// \return
///
bool DirExistEx(QString fullPath)
{<!-- -->
    QDir dir(fullPath);
    if(dir.exists())
    {<!-- -->
        return true;
    }
    else
    {<!-- -->
        //The current directory does not exist, create it, you can create multi-level directories
        bool ok = dir.mkpath(fullPath);
        return ok;
    }
}


int main(int argc, char *argv[])
{<!-- -->
    QCoreApplication a(argc, argv);

    bool isOk = DirExist("D:/1234");
    qDebug() << isOk;

    isOk = DirExistEx("D:/1/2/3");
    qDebug() << isOk;

    return a.exec();
}

DirExist function, determines whether the folder exists, and creates it if it does not exist.
DirExistEx function, determines whether the folder exists, creates it if it does not exist, and can create multi-level directories

The difference between the two is the method of creating a folder

QDir mkdir: Create a directory (folder/path)
QDir mkpath: Create multi-level directories

Qt determines whether the file exists

code show as below:

#include <QCoreApplication>
#include <QFile>
#include <QDebug>

///
/// \brief determines whether the file exists. If it does not exist, create the file.
/// \param fullFileName
/// \return
///
bool FileExist(QString fullFileName)
{<!-- -->
    QFile file(fullFileName);

    if(file.exists())
    {<!-- -->
        return true;
    }
    else
    {<!-- -->
        qDebug() << u8"The file does not exist, then create a new file";
        file.open( QIODevice::ReadWrite | QIODevice::Text );
\t\t
//Pay attention to closing the file
        file.close();
    }

    return false;
}


int main(int argc, char *argv[])
{<!-- -->
    QCoreApplication a(argc, argv);

    bool isOk = FileExist("D:/1234567.ini"); //Text type can create txt, ini, json, xml, etc.
    qDebug() << isOk;

    return a.exec();
}

When the file does not exist, calling the open method of QFile is equivalent to creating a file.

Chapter2 Qt determines whether a file or folder exists and creates a folder

Original link: https://blog.csdn.net/lusirking/article/details/51644782

1. Determine whether the folder exists

Parameter Description:

QString fullPath;//Full path of folder
/*method 1*/
bool isDirExist(QString fullPath)
{<!-- -->
    QDir dir(fullPath);
    if(dir.exists())
    {<!-- -->
      return true;
    }
    return false;
}
/*Method 2*/
bool isDirExist(QString fullPath)
{<!-- -->
    QFileInfo fileInfo(fullPath);
    if(fileInfo.isDir())
    {<!-- -->
      return true;
    }
    return false;
}

2. Determine whether the file exists

Parameter Description:

QString fullFileName;//Full path of the file (including file name)
/*method 1*/
bool isFileExist(QString fullFileName)
{<!-- -->
    QFileInfo fileInfo(fileFullName);
    if(fileInfo.isFile())
    {<!-- -->
        return true;
    }
    return false;
}

3. Determine whether the file or folder exists (that is, it is not sure whether the string is a file or folder path)

Parameter Description:

QString fullFilePath;//path name
/*method 1*/
bool isFileExist(QString fullFilePath)
{<!-- -->
    QFileInfo fileInfo(fullFilePath);
    if(fileInfo.exists())
    {<!-- -->
        return true;
    }
    return false;
}
/*Method 2*/
bool isFileExist(QString fullFilePath)
{<!-- -->
    QFile file(fullFilePath);
    if(file.exists())
    {<!-- -->
        return true;
    }
    return false;
}

4. Determine whether the folder exists, create it if it does not exist

/*Method 1*/
bool isDirExist(QString fullPath)
{<!-- -->
    QDir dir(fullPath);
    if(dir.exists())
    {<!-- -->
      return true;
    }
    else
    {<!-- -->
       bool ok = dir.mkdir(fullPath);//Only create a first-level subdirectory, that is, the upper-level directory must exist
       return ok;
    }
}
/*method 1*/
bool isDirExist(QString fullPath)
{<!-- -->
    QDir dir(fullPath);
    if(dir.exists())
    {<!-- -->
      return true;
    }
    else
    {<!-- -->
       bool ok = dir.mkpath(fullPath);//Create a multi-level directory
       return ok;
    }
}

5. The following is an excerpt of other network test codes

{<!-- -->
    QFileInfo fi("C:/123"); // Directory exists
    qDebug() << fi.isFile(); // false
    qDebug() << fi.isDir(); // true
    qDebug() << fi.exists(); // true
    qDebug() << fi.isRoot(); // false
    qDebug() << QFile::exists("C:/123"); // true
    qDebug() << QDir("C:/123").exists(); // true

    fi.setFile("C:/ABC"); // The directory does not exist
    qDebug() << fi.isFile(); // false
    qDebug() << fi.isDir(); // false
    qDebug() << fi.exists(); // false
    qDebug() << fi.isRoot(); // false
    qDebug() << QFile::exists("C:/ABC"); // false
    qDebug() << QDir("C:/ABC").exists(); // false

    fi.setFile("C:/"); // Existing drive
    qDebug() << fi.isFile(); // false
    qDebug() << fi.isDir(); // true
    qDebug() << fi.exists(); // true
    qDebug() << fi.isRoot(); // true
    qDebug() << QFile::exists("C:/"); // true
    qDebug() << QDir("C:/").exists(); // true

    fi.setFile("Z:/"); // Non-existent drive
    qDebug() << fi.isFile(); // false
    qDebug() << fi.isDir(); // false
    qDebug() << fi.exists(); // false
    qDebug() << fi.isRoot(); // false
    qDebug() << QFile::exists("Z:/"); // false
    qDebug() << QDir("Z:/").exists(); // false

    fi.setFile("C:/123.lnk"); // The shortcut exists and the file pointed to also exists
    qDebug() << fi.isFile(); // true
    qDebug() << fi.isDir(); // false
    qDebug() << fi.exists(); // true
    qDebug() << fi.isRoot(); // false
    qDebug() << QFile::exists("C:/123.lnk"); // true
    qDebug() << QDir("C:/123.lnk").exists(); // false

    fi.setFile("C:/456.lnk"); // The shortcut exists but the file pointed to does not exist
    qDebug() << fi.isFile(); // false
    qDebug() << fi.isDir(); // false
    qDebug() << fi.exists(); // false
    qDebug() << fi.isRoot(); // false
    qDebug() << QFile::exists("C:/456.lnk"); // false
    qDebug() << QDir("C:/456.lnk").exists(); // false
}

As you can see, what is easily confusing is the exists method. This method is a general judgment method and can be regarded as an expression like this
exists() == (isFile() || isDir())

That is to say, it is not rigorous to simply use the exists method to determine whether a file or folder exists
For example, your original intention is to determine whether the file exists, but the file does not exist, and there happens to be a folder with the same name, then exists will also return true. The same goes for folders

A summary based on the above code

Accurately determine whether the file exists

1. Use the QFileInfo::isFile() method

Accurately determine whether the folder exists

1. Use the QFileInfo::isDir() method
2. Use the QDir::exists() method

Not sure if the string is a file or folder path

1. Use the QFileInfo::exists() method
2. Use the QFile::exists() method