CloseHandle Function

Syntax

BOOL CloseHandle(
  HANDLE hObject
);
                

Parameters

Return Value

If the function succeeds, the return value is nonzero. If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

The CloseHandle function closes an open object handle. Closing an object handle does not close the object itself. The system closes the object when the last handle to it is closed.

It is important to close handles when they are no longer needed to free up system resources. Failing to close handles can lead to resource leaks and performance degradation.

This function is used to close handles to various types of objects, including:

• Files (CreateFile)
• Events (CreateEvent)
• Mutexes (CreateMutex)
• Semaphores (CreateSemaphore)
• Threads (CreateThread)
• Processes (CreateProcess)
• Sockets (socket)

Example

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

int main() {
    HANDLE hFile = CreateFile(
        L"my_document.txt",       // File name
        GENERIC_READ | GENERIC_WRITE, // Read and write access
        0,                        // Do not share
        NULL,                     // Default security attributes
        CREATE_ALWAYS,            // Overwrite if exists
        FILE_ATTRIBUTE_NORMAL,    // Normal file
        NULL                      // No template file
    );

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

    printf("File handle created successfully.\n");

    // ... perform operations on the file ...

    // Close the file handle when done
    if (CloseHandle(hFile)) {
        printf("File handle closed successfully.\n");
    } else {
        printf("Error closing file handle: %lu\n", GetLastError());
    }

    return 0;
}