Understanding a self-deleting program in C++ - c++

Question

There is a self deleting program
#include <windows.h>
#include <stdio.h>
void main(int argc, char* argv[])
{
STARTUPINFO si = {0};
PROCESS_INFORMATION pi = {0};
si.cb = sizeof(si);
if (argc == 1)
{
SECURITY_ATTRIBUTES sa;
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = NULL;
sa.bInheritHandle = TRUE;
CopyFile(argv[0], "1.exe", FALSE);
MoveFile(argv[0], "2.exe");
CreateFile("1.exe", 0, FILE_SHARE_READ, &sa,
OPEN_EXISTING, FILE_FLAG_DELETE_ON_CLOSE, NULL);
CreateProcess(NULL, "1.exe x", NULL, NULL,
TRUE, 0, NULL, NULL, &si, &pi);
}
else if (argc == 2)
{
while(!DeleteFile("2.exe"));
CreateProcess(NULL, "net", NULL, NULL, TRUE,
DEBUG_ONLY_THIS_PROCESS, NULL, NULL, &si, &pi);
}
}
If I remove this :CreateProcess(NULL, "net", NULL, NULL, TRUE, DEBUG_ONLY_THIS_PROCESS, NULL, NULL, &si, &pi);
it can't work.
Could anyone explain to me how it works?

Answer 1

Here's an explanation (as I understand things)
void main(int argc, char* argv[])
{
STARTUPINFO si = {0};
PROCESS_INFORMATION pi = {0};
si.cb = sizeof(si);
if (argc == 1)
{
SECURITY_ATTRIBUTES sa;
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = NULL;
sa.bInheritHandle = TRUE;
// Make a copy of ourselves which we'll use to delete the version we were run from
CopyFile(argv[0], "1.exe", FALSE);
// Rename the running copy of ourself to another name
MoveFile(argv[0], "2.exe");
// Make sure we delete the copy of ourselves that's going to delete us when we die
CreateFile("1.exe", 0, FILE_SHARE_READ, &sa, OPEN_EXISTING, FILE_FLAG_DELETE_ON_CLOSE, NULL);
// Invoke the process that will delete us
// allowing it to inherit the handle we just created above.
CreateProcess(NULL, "1.exe x", NULL, NULL, TRUE, 0, NULL, NULL, &si, &pi);
}
else if (argc == 2)
{
// Wait for the original program to die (deleting us and closing a handle), then delete it
while(!DeleteFile("2.exe"));
// Launch a child process which will inherit our file handles
// -- This keeps the file handle with FILE_FLAG_DELETE_ON_CLOSE (which we inherited) alive beyond our lifetime
// this allowing us to be deleted after we've died and our own handle is closed.
CreateProcess(NULL, "notepad", NULL, NULL, TRUE, DEBUG_ONLY_THIS_PROCESS, NULL, NULL, &si, &pi);
}
}