Read File Problem

This is a discussion on Read File Problem within the C Programming forums, part of the General Programming Boards category; I am trying to get a list of numbers from a file and store each number in an array. I ...

  1. #1
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    Read File Problem

    I am trying to get a list of numbers from a file and store each number in an array.

    I think I have the structure right but I'm getting a memory referance error and the warning that comes up is:

    'l' : unrecognized character espace sequence

    what does that mean?

    here is my read_file function

    Code:
    // Read data file
    double read_file(int num_temps, double temps[])
    {
    	int i=0;
    	double temp;
    	FILE *filedata;
    
    	filedata = fopen(DATA,"r");
    	if(filedata == NULL)
    	{
    		printf("Error opening file.\n");
    	} else {
    		while (fscanf(filedata,"%lf",&temp) == 2)
    		{
    			temps[num_temps] = temp;
    			num_temps++;
    		}
    	}
    	fclose(filedata);
    	return num_temps;
    }

  2. #2
    Devil's Advocate SlyMaelstrom's Avatar
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    Is DATA declared globally?
    Sent from my iPadŽ

  3. #3
    cwr
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    What is a "memory reference error", and which line of code exactly do you get that warning on?

  4. #4
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    num_temps is probably the number of elements in the array. So using that as an index into the array will produce buffer overflow. you need a different counter that starts with 0 and goes up to, but not including, num_temps as the array index. For example
    Code:
    temps[i++] = temp;
    now change the loop to stop when i == num_temps as well as the existing condition.

    Finally, I think fscanf() will return 1, not 2, which is the nuumber of items converted.
    Last edited by Ancient Dragon; 11-29-2005 at 09:16 PM.

  5. #5
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    I made changes as suggested but still same error.

    Ok I made some changes. However no data is pulled from the text file.

    Code:
    double read_file(int num_temps, double temps[])
    {
    	int i=0;
    	double temp;
    	FILE *filedata;
    	filedata = fopen("c:\\labdata.txt","r");
    
    	if(filedata == NULL)
    	{
    		printf("Error opening file.\n");
    
    	} else {
    
    		while (fscanf(filedata,"%lf",&temp) == 1)
    		{
    			temps[i++] = temp;
    		}
    	}
    	fclose(filedata);
    	num_temps = i;
    
    	return num_temps;
    }
    Last edited by lonewolf367; 11-29-2005 at 10:51 PM. Reason: changes.

  6. #6
    Just Lurking Dave_Sinkula's Avatar
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    When would this ever be true...
    Code:
    while (fscanf(filedata,"%lf",&temp) == 2)
    ...scanning for one value and continuing only when you get two?
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

  7. #7
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    Ok, now it reads the first number in my file. But thats it...

  8. #8
    ATH0 quzah's Avatar
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    So let's see your latest code.


    Quzah.
    Hope is the first step on the road to disappointment.

  9. #9
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    Code:
    }
    
    // Read data file
    double read_file(int num_temps, double temps[])
    {
    	int i=0;
    	double temp;
    	FILE *filedata;
    	filedata = fopen("c:\\labdata.txt","r");
    
    	if(filedata == NULL)
    	{
    
    		printf("Error opening file.\n");
    
    	} else {
    
    		while ((fscanf(filedata,"%lf ",&temp)) == 1)
    		{
    			temps[i] = temp;
    			i++;
    		}
    
    	}
    
    	fclose(filedata);
    
    	num_temps = i;
    
    	return num_temps;
    
    }

  10. #10
    cwr
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    what is the complete type of the thing passed as the second parameter to the function?

    What error/warnings are you getting, and what line(s) do they refer to?

    How do you know the problem is with that function?

  11. #11
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    hmmm I copied your code and made it into a main function so I could run it, and its working fine. I added some printf's so i could see if it was working correctly, and it seemed to be. here's the code I have:

    Code:
    #include <stdio.h>
    
    int main()
    {
    	int i=0;
    	double temp;
    	FILE *filedata;
        int num_temps;
        double temps[100];
    	filedata = fopen("c:\\labdata.txt","r");
    
    	if(filedata == NULL)
    	{
    
    		printf("Error opening file.\n");
    
    	} else {
    
    		while ((fscanf(filedata,"%lf ",&temp)) == 1)
    		{
    			temps[i] = temp;
                printf("%g\n", temps[i]);
    			i++;
    		}
    
    	}
    
    	fclose(filedata);
    
    	num_temps = i;
    
    	printf("%d numbers in the file.\n", num_temps);
    
    	return 0;
    }

  12. #12
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    thanks. i got it working. just had to add a little pointer in there from my function

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