C++: Check if a file is running - c++

Question

very noob here.
Basically what I wanna do is that as soon as I run my program, it opens a txt file.
Then starts a while loop that only ends whenever I close the file.
I know this is definitely more complex to do, if possible, than what I wrote down here, but I hope to learn something new :)
#include <iostream>
#include <windows.h>
using namespace std;
main()
{
system("test.txt"); //open my file
while(ProcessIsRunning()) //???
{
cout << "Process is currently running...";
Sleep(1000);
}
cout << "Process has stopped running"; //when I close my file, exits while and outputs this
}

Answer 1

The following code is for Windows only.
bool EditFileExternallyBlocking(const TCHAR *FilePathName)
{
SHELLEXECUTEINFO ShellExecuteInfo;
ShellExecuteInfo.cbSize = sizeof(ShellExecuteInfo);
ShellExecuteInfo.fMask = SEE_MASK_NOCLOSEPROCESS;
ShellExecuteInfo.hwnd = NULL;
ShellExecuteInfo.lpVerb = _T("edit");
ShellExecuteInfo.lpFile = FilePathName;
ShellExecuteInfo.lpParameters = NULL;
ShellExecuteInfo.lpDirectory = NULL;
ShellExecuteInfo.nShow = SW_SHOWDEFAULT;
if (!ShellExecuteEx(&ShellExecuteInfo)) {
return false;
}
if (ShellExecuteInfo.hProcess == NULL) {
return false;
}
WaitForSingleObject(ShellExecuteInfo.hProcess, INFINITE);
CloseHandle(ShellExecuteInfo.hProcess);
return true;
}
bool EditFileExternallyPolling(const TCHAR *FilePathName, const std::function<void()> &Callback)
{
SHELLEXECUTEINFO ShellExecuteInfo;
ShellExecuteInfo.cbSize = sizeof(ShellExecuteInfo);
ShellExecuteInfo.fMask = SEE_MASK_NOCLOSEPROCESS;
ShellExecuteInfo.hwnd = NULL;
ShellExecuteInfo.lpVerb = _T("edit");
ShellExecuteInfo.lpFile = FilePathName;
ShellExecuteInfo.lpParameters = NULL;
ShellExecuteInfo.lpDirectory = NULL;
ShellExecuteInfo.nShow = SW_SHOWDEFAULT;
if (!ShellExecuteEx(&ShellExecuteInfo)) {
return false;
}
if (ShellExecuteInfo.hProcess == NULL) {
return false;
}
while (WaitForSingleObject(ShellExecuteInfo.hProcess, 0) == WAIT_TIMEOUT) {
Callback();
}
CloseHandle(ShellExecuteInfo.hProcess);
return true;
}
int main()
{
std::cout << "Blocking way: \n";
std::cout << std::boolalpha << EditFileExternallyBlocking(_T("G:\\test_text_file.txt")) << '\n';
std::cout << "Process has stopped running\n\n";
std::cout << "Polling way: \n";
std::cout << std::boolalpha << EditFileExternallyPolling(_T("G:\\test_text_file.txt"),
[]() {
std::cout << "Process is currently running...\n";
Sleep(1000);
}
) << '\n';
std::cout << "Process has stopped running\n\n";
return 0;
}
Output
Blocking way:
true
Process has stopped running
Polling way:
Process is currently running...
Process is currently running...
Process is currently running...
Process is currently running...
Process is currently running...
Process is currently running...
Process is currently running...
true
Process has stopped running
Other possible return values for WaitForSingleObject should be handled at release time.
References
ShellExecuteExA API
SHELLEXECUTEINFOA structure
WaitForSingleObject API