linux C++ shell example using fork()

shellforkex1.cpp

#include <iostream>
#include <string>
#include <cstring>
#include <sstream>
#include <vector>
#include <algorithm>
#include <unistd.h>
#include <sys/wait.h>
#include <signal.h>

using namespace std;

int main()
{
	signal(SIGINT, SIG_IGN);
	while (true)
	{
		string ln, str;
		pid_t pid;

		cout << ">";
		getline(cin, ln);
		istringstream is(ln);
		vector<string> vc;
		while (is >> str)
			vc.push_back(str);

		if (vc.empty()) continue;
		if (vc[0] == "quit") break;
		if (vc[0] == "cd")
		{
			const char *path;
			if (vc.size() > 1)
				path = vc[1].c_str();
			else
				path = getenv("HOME");
			if (chdir(path) < 0)
				perror("chdir()");
			continue;
		}

		pid = fork();
		if (pid < 0)
		{
			cerr << "fork() error" << endl;
			continue;
		}

		if (pid > 0)
		{
			int status;
			waitpid(-1, &status, 0);
		}
		else
		{
			signal(SIGINT, SIG_DFL);
			char **argv;
			argv = new char*[vc.size() + 1];
			for (int i = 0; i < vc.size(); i++)
			{
				argv[i] = new char[vc[i].length() + 1];
				strcpy(argv[i], vc[i].c_str());
			}

			argv[vc.size()] = NULL;
			execvp(vc[0].c_str(), argv);
			perror("execvp()");
			for (int i = 0; i < vc.size(); i++)
				delete[] argv[i];
			delete[] argv;
			exit(0);
		}
	}

	return 0;
}