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Please understand that I am asking here and it is NOT a Qt question.
My task is to start a new process - the parameters are "application" and its parameters.
The basic process builds a "Database" and I am not so sure about "bin/sh" - I guess it "runs" a shell...
It works and there is no need to get into why at this point.
The "problem" is - the "process" is running and I need to interact with it.
I can use "write" but I have no idea when and where and how.
In the enclosed snippet the "info\n" is "send" to the file ( shell?) before it is finished...
I do understand that Qt process can "wait for finished " and I can also get a SIGNAL when the file is actually done building. What I do not get - if the process is actually /physically building / writing a file - what does "wait for finished " waiting for ?
Again - I am not asking how to code Qt , I am asking how to code so I can "write" the additional stuff in right time.
I am assuming that your QP pointer is a reference to an object of QProcess Class | Qt Core 6.3.2[^]. As stated in the documentation the start method assumes the device mode as ReadWrite, which if it follows the normal rules, suggests you can write to and read from the started process. But writing will only work if the started process is waiting for input on its stdin stream. As far as I can see your started process is a simple shell pipeline to write some data to stdout and a couple of files. So it is not likely to be waiting for input from an external source.
After more research - I have two distinct usage of the "command" (QProcess) - one writes to the file and terminates and the other one is "interactive" - writes to the file and expects input.
As of now I can "monitor" the first one two ways - in code - wait for finished or using "finished" SIGNAL. Right now my SIGNAL is "readyWrite" which ( the name ) does not make much sense - BUT it works with non - interactive command. I am going to take a closer look at QProcess SIGNALs - at least make more sense with non interactive command.As of now I just start the QProcess , and I am not directly ( using SIGNALs) verifying it is actually running / started.
After I clean that up I'll take a look at interactive part. Not sure where to start.
The logical place is a tutorial on QProcess. You can only communicate with an independent process in this way, when the input and output streams are connected. The default option to the start method sets QIODeviceBase::OpenMode mode = ReadWrite. Does that mean that you can write to the process or not? Only a QT expert can advise on the answer.
I have verified that I can "write" to QProcess - the question remains when.
Until now the command I have been testing with - which is why I am reluctant to post in QT forum - has been one of the challenges. There is no definite pattern when the command is "single shot" or interactive - depends on how it has been used before.
1. Why putting #define in char "string" won't process the "command" to "start a new process" , however,
compiler is not giving an error ?
In debug mode I have literal BT_DATABASE_TEST in "command",
2. I need to make the primary text (*.txt) file a variable - how ?
#define BT_DATABASE_TEST "../../BT_DATABASE/BluetoothDatabase.txt"
constchar *command = "bluetoothctl show | tee ../../BT_DATABASE/BluetoothDatabase.txt | tee /tmp/temp";
//const char *command = "bluetoothctl show | tee BT_DATABASE_TEST | tee /tmp/temp"; won't work
QP->start("/bin/sh", QStringList() << "-c" << command);
#define BT_DATABASE_TEST "../../BT_DATABASE/BluetoothDatabase.txt"
constchar *command = "bluetoothctl show | tee " BT_DATABASE_TEXT " | tee /tmp/temp";
2. Maybe something like this:
std::string var = "blah_blah.txt";
std::string command = std::string("bluetoothctl show | tee ") + var + std::string("" | tee /tmp/temp");
QP->start("/bin/sh", QStringList() << "-c" << command.c_str());
Yes. If objects belong to different classes, the only way to store them in a container is to use pointers, because the container allocates the same amount of memory for each entry. If you also want the container to delete an entry when you erase it, declare it as, for example, vector<unique_ptr<T>>.
If you can handle raw pointers, then C++ smart pointers should be easy to understand. Google for C++ unique_pointer tutorial and read through a few of the returned hits. It's fairly straight forward, and in general new C++ development should use the smart pointers instead of using raw (e.g. new/delete).
The problem is I hate complicated syntax. Containers are already complicated syntax for me, combine that with another object (pointer) from a library and it becomes unintelligible mess. I will use a complicated feature when I really need to use it and there is no other way around it. Usually I need to use a feature a couple months before I can move on to something more complicated.