Question

How to use the CreateFile function using the Win32 API in C

Answer 1

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

int main(void)
{
    HANDLE hFile = CreateFileA(
        "data.txt",            // File name
        GENERIC_READ | GENERIC_WRITE, // Desired access
        0,                        // Share mode (0 = exclusive)
        NULL,                     // Security attributes
        CREATE_ALWAYS,            // Creation disposition
        FILE_ATTRIBUTE_NORMAL,    // Flags and attributes
        NULL                      // Template file
    );

    if (hFile == INVALID_HANDLE_VALUE) {
        printf("CreateFile failed. Error: %lu\n", GetLastError());
        return 1;
    }

    const char* text = "CreateFile Function\n";
    DWORD bytesWritten = 0;

    BOOL ok = WriteFile(
        hFile,
        text,
        (DWORD)strlen(text),
        &bytesWritten,
        NULL
    );

    if (!ok) {
        printf("WriteFile failed. Error: %lu\n", GetLastError());
        CloseHandle(hFile);
        return 1;
    }

    printf("Wrote %lu bytes.\n", bytesWritten);

    CloseHandle(hFile);

    return 0;
}



/*
run:

Wrote 20 bytes.

*/

 

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