<s>[INST] This problem is trying to demonstrate the use of pidfile on a Unix system. It is intended to be executed from the command line.
```
#include <iostream>
#include <string>
#include <fstream>
#include <sys/stat.h>
#include <unistd.h>

void createPidFile(const std::string& pidFilePath) {
    std::ofstream pidFile(pidFilePath);
    if (!pidFile.is_open()) {
        std::cout << "Error opening pid file for writing: " << pidFilePath << std::endl;
        exit(1);  // exit if cannot open pid file
    }
    pidFile << getpid() << std::endl;
    pidFile.close();
}

void deletePidFile(const std::string& pidFilePath) {
    if (remove(pidFilePath.c_str()) != 0) {
        std::cout << "Error removing pid file: " << pidFilePath << std::endl;
        exit(1);  // exit if cannot remove pid file
    }
}

int main(int argc, char** argv) {
    if (argc != 2) {
        std::cout << "Usage: " << argv[0] << " <pidfile>" << std::endl;
        return 1;
    }

    std::string pidFilePath = argv[1];

    // Check if pid file already exists
    struct stat buffer;
    if (stat(pidFilePath.c_str(), &buffer) != 0) {
        // pid file does not exist - create it
        createPidFile(pidFilePath);
    } else {
        // pid file already exists
        // read pid from file
        std::ifstream pidFile(pidFilePath);
        if (!pidFile.is_open()) {
            std::cout << "Error opening pid file for reading: " << pidFilePath << std::endl;
            exit(1);  // exit if cannot open pid file
        }
        int existingPid;
        pidFile >> existingPid;
        pidFile.close();

        // check if process with existing pid still exists
        char cmd[50];
        sprintf(cmd, "ps -p %d > /dev/null", existingPid);
        if (system(cmd) != 0) {
            // process do not exist - remove pid file
            deletePidFile(pidFilePath);
            createPidFile(pidFilePath);
        } else {
            // process still exists - exit
            std::cout << "Another instance of the process is already running with PID: " << existingPid << std::endl;
            return 1;
        }
    }

    // main loop
    while (true) {
        // do something
    }

    return 0;
}
```
This code will run indefinitely, holding the process ID in the pid file. What are the problems with this code?[/INST]