Issues using fstream

p8ntballsniper8 · #1 04-Nov-2009, 14:27

So I'm trying to write a program that will read in a character from another file, and then test to see if it's a number, letter, operator, etc etc.

The file I'm getting my input from is a short program that uses a random number generator to output a random character each time it's run. I'm having trouble getting my character variable input into my actual program.

Here's my RNG code: <character.cpp>

CPP / C++ / C Code:

#include <iostream>
#include <ctime>
using namespace std;

int main()
{
srandom(time(NULL));
char x;
x =(random()%128);
cout <<x<<endl;
}

and here's my test program code:

CPP / C++ / C Code:

#include <iostream>
#include <fstream>

using namespace std;

void ShowHeader(); //declaring show header function

int main()
{
ShowHeader(); //initializing header function

ifstream inputStream;

inputStream.open("character.cpp");

if(inputStream.is_open())
{
cout <<"The file is open"<<endl;
inputStream >> x;
cout<<x;
}

x is obviously the variable I'm trying to get from character.cpp, but the cout line for some reason won't output anything, the only output I get is my assignment header and 'The file is open'.

What is it I'm doing wrong? I've never used fstream before so...

Thank you

Howard_L · #2 04-Nov-2009, 23:32

character.cpp only writes one character to the screen (stdout) and NOT to a file, is that what you wanted ?
The second program opens the character.cpp and reads one char of that, not the output x.

Here is an example of setting up a loop to write "count" number of characters to the screen and at the bottom I show how you can redirect that output to a file.

CPP / C++ / C Code:

#include <iostream>  // character.cpp
#include <ctime>
using namespace std;

int main()
{
  srandom(time(NULL));
  char i, x, count = 15;

  for(i = 0; i < count; i++)
  {
    x =(random()%128);
    // cout << (int)x << " ";   // cast x to int to see the ascii code value
    cout << x << " ";           // otherwise this prints the ascii character
  }
  cout << endl;

  return 0;
}
/*
Use > to redirect this output to a file:
  character.exe > character.dat
*/

Next is an example of opening that file and reading one character at a time until EOF is reached.:

CPP / C++ / C Code:

 #include <iostream>
#include <fstream>

using namespace std;

void ShowHeader() { cout << "What the heck is showheader? \n\n"; }  //declaring show header function

int main()
{
  int x;  // must use int size instead of char to "fit" the EOF value.

  ShowHeader(); //initializing header function NOT... YOU'RE "CALLING" IT
 
  ifstream inputStream;

  inputStream.open("character.dat");

  if(inputStream.is_open())
  {
    cout <<"The file is open"<<endl;
    
    while ( (x = inputStream.get()) != EOF)
    {
      cout << (char)x;
    } 
    cout <<  endl;  

    inputStream.close();
  }
  else
  {
    cout << "Problem opening file... " << endl;
  }
  return 0;
}

And here's a sample run:

Code:

~>   character.exe  >  character.dat

~>  cat character.dat
u g  ( E l  B 6 v n . 5 . a 

~>  readchars.exe
What the heck is showheader? 

The file is open
u g  ( E l  B 6 v n . 5 . a

See if that will get you going.

p8ntballsniper8 · #3 09-Nov-2009, 09:28

Ah, thank you. That worked quite well.

And to answer your question, ShowHeader was a function that was required for me to put it, that was simply three cout commands that put my name, date, etc. at the top of the programs output.

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Issues using fstream

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Re: Issues using fstream