c言語のいくつかのファイル操作関数について

HANDLE CreateFile( LPCTSTR lpFileName, DWORD dwDesiredAccess, DWORD dwShareMode, LPSECURITY_ATTRIBUTES lpSecurityAttributes, DWORD dwCreationDisposition, DWORD dwFlagsAndAttributes, HANDLE hTemplateFile
); 

 。。。。

 
BOOL WriteFile( HANDLE hFile, LPCVOID lpBuffer, DWORD nNumberOfBytesToWrite, LPDWORD lpNumberOfBytesWritten, LPOVERLAPPED lpOverlapped
); 
  
 。。
  
 
  
#include <windows.h>
#include <tchar.h>
#include <stdio.h>

void __cdecl _tmain(int argc, TCHAR *argv[])
{
    HANDLE hFile; 
    char DataBuffer[] = "This is a test string.";
    DWORD dwBytesToWrite = (DWORD)strlen(DataBuffer);
    DWORD dwBytesWritten = 0;

    printf("/n");
    if( argc != 2 )
    {
        printf("ERROR:/tIncorrect number of arguments/n/n");
        printf("%s <file_name>/n", argv[0]);
        return;
    }

    hFile = CreateFile(argv[1],                // name of the write
                       GENERIC_WRITE,          // open for writing
                       0,                      // do not share
                       NULL,                   // default security
                       CREATE_ALWAYS,          // overwrite existing
                       FILE_ATTRIBUTE_NORMAL,  // normal file
                       NULL);                  // no attr. template

    if (hFile == INVALID_HANDLE_VALUE) 
    { 
        printf("Could not open file (error %d)/n", GetLastError());
        return;
    }

    _tprintf(TEXT("Writing %d bytes to %s./n"), dwBytesToWrite, argv[1]);

    // This loop would most likely never repeat for this synchronous example.
    // However, during asynchronous writes the system buffer may become full,
    // requiring additional writes until the entire buffer is written.

    while (dwBytesWritten < dwBytesToWrite)
    {
        if( FALSE == WriteFile(hFile,           // open file handle
                               DataBuffer + dwBytesWritten,     // start of data to write
                               dwBytesToWrite - dwBytesWritten, // number of bytes to write
                               &dwBytesWritten, // number of bytes that were written
                               NULL)            // no overlapped structure
          )
        {
            printf("Could not write to file (error %d)/n", GetLastError());
            CloseHandle(hFile);
            return;
        }
    }

    _tprintf(TEXT("Wrote %d bytes to %s successfully./n"), dwBytesWritten, argv[1]);

    CloseHandle(hFile);
}

Example: Open a File for Reading
The following example uses CreateFile to open an existing file for reading and ReadFile to read up to 80 characters synchronously from the file.

In this case, CreateFile succeeds only if the specified file already exists in the current directory. A subsequent call to open this file with CreateFile will succeed if the call uses the same access and sharing modes.

Tip: You can use the file you created with the previous WriteFile example to test this example.


#include <windows.h>
#include <tchar.h>
#include <stdio.h>

#define BUFFER_SIZE 81

void __cdecl _tmain(int argc, TCHAR *argv[])
{
    HANDLE hFile; 
    DWORD dwBytesRead = 0;
    char ReadBuffer[BUFFER_SIZE] = {0};

    printf("/n");
    if( argc != 2 )
    {
        printf("ERROR:/tIncorrect number of arguments/n/n");
        printf("%s <text_file_name>/n", argv[0]);
        return;
    }

    hFile = CreateFile(argv[1],               // file to open
                       GENERIC_READ,          // open for reading
                       FILE_SHARE_READ,       // share for reading
                       NULL,                  // default security
                       OPEN_EXISTING,         // existing file only
                       FILE_ATTRIBUTE_NORMAL, // normal file
                       NULL);                 // no attr. template
 
    if (hFile == INVALID_HANDLE_VALUE) 
    { 
        printf("Could not open file (error %d)/n", GetLastError());
        return; 
    }

    // Read one character less than the buffer size to save room for
    // the terminating NULL character.

    if( FALSE == ReadFile(hFile, ReadBuffer, BUFFER_SIZE-1, &dwBytesRead, NULL) )
    {
        printf("Could not read from file (error %d)/n", GetLastError());
        CloseHandle(hFile);
        return;
    }

    if (dwBytesRead > 0)
    {
        ReadBuffer[dwBytesRead+1]='/0'; // NULL character

        _tprintf(TEXT("Text read from %s (%d bytes): /n"), argv[1], dwBytesRead);
        printf("%s/n", ReadBuffer);
    }
    else
    {
        _tprintf(TEXT("No data read from file %s/n"), argv[1]);
    }

    CloseHandle(hFile);
}