Hello I'm writing a short program to implement a shell and I'm running into an unusual problem. For some reason I can't clear to the std::cout buffer. The program wont print out messages. I understand a simple solution is to switch to std::cerr, but is there a way to get messages to print with cout? Things I've tryed:
std::cout.flush()
std::endl
after anything is written to standard out. std::flush
into the output stream std::cout.setf(std::ios::unitbuf);
which was something I found that should unbuffer output.Any help is much appreciated here is my code:
int main()
{
//Tryed this to unbuffer cout, no luck.
std::cout.setf(std::ios::unitbuf);
std::string input;
//Print out shell prompt and read in input from keyboard.
std::cout << "myshell> ";
std::getline(std::cin, input);
//**********************************************************************
//Step 1) Read in string and parse into tokens.
//**********************************************************************
char * buf = new char[input.length() + 1];
strcpy(buf, input.c_str());
int index = 0;
char * command[256];
command[index] = std::strtok(buf, " "); //Get first token.
std::cout << command[index] << std::endl;
while (command[index] != NULL)
{
++index;
command[index] = std::strtok(NULL," "); //Get remaining tokens.
std::cout << command[index] << std::endl;
}
std::cout.flush(); //No luck here either
//HERE IS WHERE MY PROBLEM IS.
std::cout << index << " items were added to the command array" << std::endl;
delete[] buf;
return 0;
}
The problem is that you're sending NULL
to cout
on the last iteration of the while
loop, which leads to UB, and in your case is jamming cout
. Check for NULL
before you send anything to cout
and you're fine:
if (command[index] != NULL) {
std::cout << command[index] << std::endl;
}