#include <unistd.h>
#include <fcntl.h>

#include <list>
#include <utility>

using std::list;
using std::pair;
using std::make_pair;

static list<pair<int,int> > redirs;

void Redirect(int fd, const char *fn, int mode)
{
    int d = dup(fd);
    int f = open(fn, mode, 0644);
    dup2(f, fd);
    
    redirs.push_front(make_pair(fd, d));
}

void RedirectOut(int fd, const char *fn)
{
    Redirect(fd, fn, O_WRONLY | O_CREAT | O_TRUNC);
}

void RedirectIn(int fd, const char *fn)
{
    Redirect(fd, fn, O_RDONLY);
}

void Redirect(int fd, const char *fn)
{
    Redirect(fd, fn, O_RDWR | O_CREAT | O_APPEND);
}

void Unredirect(int fd)
{
    list<pair<int, int> >::iterator i;
    for(i=redirs.begin(); i!=redirs.end(); ++i)
        if(i->first == fd)
        {
            dup2(i->second, fd);
            close(i->second);
            redirs.erase(i);
            return;
        }
}