Print a GUID variable

Question

I have a GUID variable and I want to write inside a text file its value. GUID definition is:

typedef struct _GUID {          // size is 16
    DWORD Data1;
             


        

Answer 1

In case when your code uses ATL/MFC you also could use CComBSTR::CComBSTR(REFGUID guid) from atlbase.h:

GUID guid = ...;
const CComBSTR guidBstr(guid);  // Converts from binary GUID to BSTR
const CString guidStr(guidBstr); // Converts from BSTR to appropriate string, ANSI or Wide

It will make conversion & memory cleanup automatically.

Answer 2

Use the StringFromCLSID function to convert it to a string

e.g.:

GUID guid;
CoCreateGuid(&guid);

OLECHAR* guidString;
StringFromCLSID(guid, &guidString);

// use guidString...

// ensure memory is freed
::CoTaskMemFree(guidString);

Also see the MSDN definition of a GUID for a description of data4, which is an array containing the last 8 bytes of the GUID

Answer 3

Use UuidToString function to convert GUID to string. The function accepts UUID type which is typedef of GUID.

Answer 4

You can eliminate the need for special string allocations/deallocations by using StringFromGUID2()

GUID guid = <some-guid>;
// note that OLECHAR is a typedef'd wchar_t
wchar_t szGUID[64] = {0};
StringFromGUID2(&guid, szGUID, 64);

Answer 5

Sometimes its useful to roll your own. I liked fdioff's answer but its not quite right. There are 11 elements of different sizes.

printf("Guid = {%08lX-%04hX-%04hX-%02hhX%02hhX-%02hhX%02hhX%02hhX%02hhX%02hhX%02hhX}", 
  guid.Data1, guid.Data2, guid.Data3, 
  guid.Data4[0], guid.Data4[1], guid.Data4[2], guid.Data4[3],
  guid.Data4[4], guid.Data4[5], guid.Data4[6], guid.Data4[7]);

Output: "Guid = {44332211-1234-ABCD-EFEF-001122334455}"

Refer to Guiddef.h for the GUID layout.

Same, as a method:

void printf_guid(GUID guid) {
    printf("Guid = {%08lX-%04hX-%04hX-%02hhX%02hhX-%02hhX%02hhX%02hhX%02hhX%02hhX%02hhX}", 
      guid.Data1, guid.Data2, guid.Data3, 
      guid.Data4[0], guid.Data4[1], guid.Data4[2], guid.Data4[3],
      guid.Data4[4], guid.Data4[5], guid.Data4[6], guid.Data4[7]);
}

you can also pass a CLSID to this method.

Answer 6

Courtesy of google's breakpad project:

std::string ToString(GUID *guid) {
    char guid_string[37]; // 32 hex chars + 4 hyphens + null terminator
    snprintf(
          guid_string, sizeof(guid_string),
          "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
          guid->Data1, guid->Data2, guid->Data3,
          guid->Data4[0], guid->Data4[1], guid->Data4[2],
          guid->Data4[3], guid->Data4[4], guid->Data4[5],
          guid->Data4[6], guid->Data4[7]);
    return guid_string;
}

UUID guid = {0};
UuidCreate(&guid);
std::cout << GUIDToString(&guid);