File Reading Errors

This is a discussion on File Reading Errors within the Game Programming forums, part of the General Programming Boards category; When I run this code: Code: #include <stdio.h> #include <stdlib.h> #include <fstream.h> #include <iostream.h> #include <time.h> #include <string.h> int main() ...

  1. #1
    . Driveway's Avatar
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    Question File Reading Errors

    When I run this code:


    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <fstream.h> 
    #include <iostream.h> 
    #include <time.h> 
    #include <string.h>
    
    
    int main()
    {
    	srand((unsigned)time(NULL));
    	int x=rand()%9;
    	ofstream value("xvalue.txt", ios::ate | ios::in, filebuf::sh_write );
    	if(!value.is_open())
    	{
    	   cout<<"Could not open file...  Error.... Quitting\n";
    	   system("PAUSE");
    	   return 0;
    	}
    	value<<x<<";";
    	value.close();
    	char yes;
    	cout<<"Would you like to view contents of file (up to 200 characters in)?\n y for yes, anything else for quit\n";
    	cin>>yes;
    	if (yes=='y' || yes== 'Y')
    	{
    		char text[200];
    		ifstream read_value("xvalue.txt", ios::out | ios::nocreate);
    		if (!read_value.is_open())
    		{
    			printf("Error opening file\n");
    			system("PAUSE");
    			return 0; 
    		}
            read_value>>text;
    		for (int i=0; i<=200; i++)
    		printf("%c", text[i]);
    		printf("\n\n");
    		read_value.close();
            system("PAUSE");	
    		printf("\n\nWould you like to delete the contents of the file?");
    		cin>>yes;
            if (yes== 'y' || yes=='Y')
           read_value.clear(0);
     	}
    	return 0;
    }
    I get what I want, but if I have any spaces in the file it stops reading there. Also, if I read a file it reads what's in it, and then adds some various characters. How can I fix both of these problems?
    Last edited by Driveway; 05-24-2002 at 03:40 PM.

  2. #2
    Registered User Invincible's Avatar
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    First of all...

    You are mixing C and C++ I/O. This is not good practice. The function printf from the stdio library is a C function. Use cout instead. The declaration of read_value(file, ios::in) to open a file is also a C type function. Use read_value.open(file, ios::in) instead.

    Secondly, your app quits reading at whitespaces because the >> operator treats them as a delimiter. To avoid this use either the file.getline() or file.get() function.

    Here is the reason you're getting garbage for output:
    Code:
    for (int i=0; i<=200; i++)
    printf("%c", text[i]);
    You're telling printf to output 199 chars when you have only 2 (or however many are stored in your file) stored in the array. The rest of the chars you're outputting are null characters.

    Lastly, fstream.clear() doesn't delete the contents of a file like you might think it would. The clear function is actually used to clear the filestream buffer.

    Take a close look at the code below. It's well commented.

    Code:
    //include our headers using the standard namespace
    #include <cstdlib>
    #include <fstream> 
    #include <iostream>//exclude <stdio.h> since we're using <iostream>
    #include <ctime> 
    using namespace std;
    //the std namespace also includes some basic 
    //string functions like stricmp() and stcmp()
    
    int main()
    {	
    	ofstream value;//declare our output stream
            ifstream read_value;//declare our input stream
    	char yes[1];//set aside an array for yes
    	int x;//for our random number
    
    	srand((unsigned)time(NULL));
                    x = rand()%9;
    
    	value.open("xvalue.txt", ios::out | ios::app );
            //use the open function, app is preferred to ate
    
    	if(!value.is_open())
    	{
    	   cout << "Could not open file...  Error.... Quitting\n";
    	   exit(0);//exit if our file doesn't open
    	}
    
    	value << x << ";";
    
    	value.close();
    
    	cout << "Would you like to view contents of file " 
    		 << "(up to 200 characters in)?\n\nY for yes, "
    		 << " anything else for quit: ";
    
    	cin >> yes;
    	cin.get();
            //cin leaves the \n character in the buffer, 
            //so we call cin.get to remove it
    	cout << "\n";
    
    	if (stricmp(yes, "Y") == NULL)
            //"stricmp()" compares two character strings. 
            //Case is ignored as opposed to "strcmp()," 
            //which is case sensitive. It returns 
            //NULL or 0 if the two strings are equal.
    	{	
    		char text[200];
    		read_value.open("xvalue.txt", ios::in );
    		if (!read_value.is_open())
    		{
    			cout << "Error opening file\n";
    			exit(0); 
    		}
            read_value.getline(text, 200);
            //here we pass our character array and its size to
            //read_value.getline(). This will read characters into
            //the array until it reaches the delimiter. The delimiter
            //is set to "\n" by default but can be changed by 
            //overloading the function.
    
    	cout << text << "\n\n";
            //output the text to the screen and we are done.
            //Good work!
    
    	read_value.close();
    	}
    	
    	return 0;
    }
    Last edited by Invincible; 05-25-2002 at 04:14 AM.
    "The mind, like a parachute, only functions when open."

  3. #3
    . Driveway's Avatar
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    OK, that works...
    But there is still one problem...
    A runtime error....
    After it displays the file, I get:
    Run-Time Check Failure #2 - Stack around the variable 'yes' was corrupted.

    And then it freezes for a while and exits.

    [EDIT]
    I'm am using VC++ .NET. It's being run in debug mode. When I do it in release it works just fine...

    [/EDIT]
    Last edited by Driveway; 05-25-2002 at 07:42 AM.

  4. #4
    Registered User Invincible's Avatar
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    Hmm...

    It sounds like you're exceeding the bounds of your array. Tell me if I'm wrong, but and array of size[1] has two members [0] and [1] right? So the "Y" the user enters gets stored in [0] and [1] is reserved for the null char.

    Did you change the size of the "yes" array?

    Perhaps try increasing the variable size of "yes" to yes[2]. Or bigger, just in case the user tries to enter garbage. Say yes[20].

    Let me know if that doesn't work.
    "The mind, like a parachute, only functions when open."

  5. #5
    . Driveway's Avatar
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    It worked, but before I was just just typing y and I got that error. Oh well, it works now. Also how would I make a sub-directory?

    ex:

    the .exe is at C:\MyProgs\Prog00\

    and I want the text file at C:\MyProgs\Prog00\Saves

    How would I do that?
    Last edited by Driveway; 05-25-2002 at 05:09 PM.

  6. #6
    Registered User Invincible's Avatar
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    It's simple

    value.open("saves/xvalue.txt", ios::in | ios::app);

    That's all there is to it.
    "The mind, like a parachute, only functions when open."

  7. #7
    . Driveway's Avatar
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    Oh I was trying to use the backslash:
    value.open("saves\\xvalue.txt", ect)

    the two back-slashes is obvious, the escape character.
    Just wondering: Was the Dev C++ compiler created using assembly or C++? I'm asuming assembly.

  8. #8
    . Driveway's Avatar
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    Unhappy

    I tried your directory thing but it didn't work. I don't know why.

  9. #9
    Registered User Invincible's Avatar
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    To my knowledge, but don't quote me, compilers are created in assembly yes. The only langauges that are based on other langauges are called scripts. Again don't quote me.

    Are you using a double forward slash like you did in the your example above? Or were you just trying to escape to back-slash in that example? It is one forward-slash between the directory and the file surrounded in quotes. At least on my compiler and system. Using VS6 on XP.

    Either way, did you create a folder called "saves" and put your file in it?
    "The mind, like a parachute, only functions when open."

  10. #10
    . Driveway's Avatar
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    OK, it's working now, I didn't know you had to create the folder. I thought it would make it for you like it makes files for you if they don't exsist

  11. #11
    . Driveway's Avatar
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    Another question: How do you run .exe from a .exe with C++.

    http://cprogramming.com/boardfaq.html#execs

    It tells you how to run exes from a exe.
    I've tried both but neither work. Is there a way that works?

    BTW: Something else useful there is it tells you how to make a gotoxy() function, it's quite simple really

  12. #12
    Registered User Invincible's Avatar
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    The syntax for using the system command is different from opening a file, in this case you do use the escape character. You must also specify the directory where the exec is located. Unless it's in the same folder as the one you're running I think.

    system("C:\\Games\\StarWarsJK2\\JediOutcast.exe");
    "The mind, like a parachute, only functions when open."

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