C++ variant of Figure 3.8

forking.cpp

#include <cstdlib>
#include <iostream>

#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

using std::cout;
using std::cerr;
using std::endl;

int main(int argc, char *argv[])
{
    if (argc != 2) {
        cerr << "Usage: " << argv[0] << " PATHNAME" << endl;
        return EXIT_FAILURE;
    }
    auto pathname = argv[1];

    auto child_pid = fork();
    if (child_pid < 0) {
        perror("fork");
        return EXIT_FAILURE;
    }

    if (child_pid == 0) {
        cout << "CHILD: child_pid = " << child_pid << "." << endl;

        auto pid = getpid();
        cout << "CHILD: pid = " << pid << "." << endl;

        cout << "CHILD: executing " << pathname << endl;
        auto ok = execl(pathname, pathname, NULL);
        if (ok < 0) {
            perror(pathname);
            return EXIT_FAILURE;
        }
    } else { // child_pid > 0
        cout << "PARENT: child_pid = " << child_pid << "." << endl;

        int status;
        auto ok = wait(&status);
        if (ok < 0) {
            perror("wait");
            return EXIT_FAILURE;
        }

        cout << "PARENT: child exited with status " << WEXITSTATUS(status) << "." << endl;
    }

    return EXIT_SUCCESS;
}