Good code to limit logins of users on FreeBSD ( http://forums.freebsd.org/showthread.php?t=23683 )

gistfile1.c

#include <iostream>
#include <string>

using namespace std;

string Exec(const char *cmd);
void ReplaceAll(string& str, const string& from, const string& to);

int main(int argc, char **argv, char **envp) {
        string whoami, users;
        size_t found;
        size_t pos1, pos2;

        whoami = Exec("whoami");
        users = Exec("who");

        ReplaceAll(whoami, "\n", "");

        pos1 = users.find(whoami.c_str());
        pos2 = users.rfind(whoami.c_str());

        if (pos1 != pos2) {
                cout << endl
                        << "  * Too many logins for " + whoami
                        << endl
                        << "  * Forcing logout..."
                        << endl
                        << endl
                        << endl;

                char command[100];
                sprintf(command, "pkill -9 -U %d '.*'", getuid());
                system(command);
        }

        return 0;
}

string Exec(const char *cmd) {
        FILE *pipe = popen(cmd, "r");
        if (!pipe)
                return "3rr0r";

        char buffer[128];
        string result = "";
        while (!feof(pipe)) {
                if (fgets(buffer, 128, pipe) != NULL)
                        result += buffer;
        }

        pclose(pipe);
        return result;
}

void ReplaceAll(string& str, const string& from, const string& to) {
    size_t start_pos = 0;
    while((start_pos = str.find(from, start_pos)) != string::npos) {
        size_t end_pos = start_pos + from.length();
        str.replace(start_pos, end_pos, to);
        start_pos += to.length();
    }
}