SetFileSize function

Namespace: Windows::Storage

Header: fileapi.h

Syntax

BOOL SetFileSize(
    HANDLE hFile,
    LARGE_INTEGER liSize
);

Parameters

Parameter	Type	Description
hFile	HANDLE	Handle to the file. The handle must have `GENERIC_WRITE` access.
liSize	LARGE_INTEGER	New size for the file, in bytes.

Return value

Returns nonzero if successful; otherwise, 0. Use GetLastError for extended error information.

Remarks

The function changes the physical size of the file. If the new size is smaller, the file is truncated. If larger, the file is extended and the contents of the new area are undefined.

This function is a wrapper around SetEndOfFile and SetFilePointerEx. When possible, prefer the newer API calls for better compatibility.

Example

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

int main()
{
    HANDLE h = CreateFileW(L"example.txt",
                            GENERIC_WRITE,
                            0,
                            NULL,
                            OPEN_EXISTING,
                            FILE_ATTRIBUTE_NORMAL,
                            NULL);
    if (h == INVALID_HANDLE_VALUE) {
        wprintf(L"CreateFile failed: %lu\\n", GetLastError());
        return 1;
    }

    LARGE_INTEGER newSize;
    newSize.QuadPart = 1024 * 1024; // 1 MB

    if (!SetFileSize(h, newSize)) {
        wprintf(L"SetFileSize failed: %lu\\n", GetLastError());
        CloseHandle(h);
        return 1;
    }

    wprintf(L"File size set to 1 MB.\\n");
    CloseHandle(h);
    return 0;
}