Programming

	//save in/out
	int tmpin = dup(0);
	int tmpout = dup(1);
	
	//set initial input
	int fdin;
	if(_inputFile)
	{
	   fdin = open(_inputFile, O_RDONLY | O_CREAT, S_IREAD | S_IWRITE);
	}
	else
	{
	   //use default input
	   fdin = dup(tmpin);
	}

	int ret;
	int fdout;
	for(int i = 0; i < _numberOfSimpleCommands; i++)
	{
	   //redirect input
	   dup2(fdin, 0);
	   close(fdin);
	   //setup output
	   if(i == _numberOfSimpleCommands-1) 
	   {// last command must be set so output redirection is set

	      if(_outFile)
	      {
	         fdout = open(_outFile, O_WRONLY | O_CREAT, S_IREAD | S_IWRITE);
	      }
	      else
	      {  
	         fdout = dup(tmpout);
	      }
	   }
	   else
	   {
                   //simple command
	      //create pipe
	      int fdpipe[2];
	      pipe(fdpipe);
                  fdout = fdpipe[0];
                  fdin = fdpipe[1];
	    }

	    //redirect output
	    dup2(fdout, 1);
	    close(fdout);

	    //create child process
	    ret = fork();
	    if(ret == 0)
	    {
	       execvp((*_simpleCommands)[i]._arguments[0],(*_simpleCommands)[i]._arguments);
	       perror("execvp");
	       exit(1);
	     }//if ret
	}//for

	//restore in/out defaults
	dup2(tmpin, 0);
	dup2(tmpout, 1);
	close(tmpin);
	close(tmpout);
	
	if(!_background)
	{
		//wait for last command
		waitpid(ret, 0, 0);
	}

.....
ret=fork();
fprintf(stderr,"pid=%d,ppid=%d,tmpin=%d,tmpout=%d\n",
getpid(),getppid(),tmpin,tmpout);
fflush(stderr);
if (ret==0)
...