CODEWITHSUNDEEP
cfileprintf
shiran bar
shiran bar

Reputation: 29

problem using fprintf

I'm trying to print to a text file numerous variables yet it doesn't work. I checked and verified that i write it in the correct syntax. I also checked the return value and it's positive therefore i know it did write to the file, however when i open the file it's empty.

I would be happy for some help. This is the code:

I initiate DynsaleDayPtr in the main: 

FILE* DynsaleDayPtr = CreateTextFiles("sale_day.txt");

Create function: 

FILE* CreateTextFiles (char* fileName)  
{  
    FILE* saleFilePtr=NULL;  

    if((saleFilePtr=fopen(fileName,"a+"))==NULL)  
        printf("File couldn't be opened\n");  
    return saleFilePtr;  
}

The call to the function TextAddSale is done from a function that is called in the main:
TextAddSale(DynSaleDayPtr,dynNumOfRecords); 

Bool TextAddSale (FILE* DynsaleDayPtr, int* dynNumOfRecords)  
{  

    char id[6];  
    char name [50];  
    char priceChar[20];  
    char* tmp = NULL;  
    int price=-1;  
    DynamicRecord * newRec=NULL;  

    scanf("%s%s%s",id,name,priceChar);

    newRec = (DynamicRecord *)malloc(sizeof(DynamicRecord));  
    if (newRec == NULL)  
        return False;  
    tmp = (char*)malloc(strlen(name)+1);  
    if (tmp == NULL)  
    {  
        free (newRec);  
        return False;  
    }  
    strcpy(tmp,name);  
    newRec->productName = tmp;  
    strcpy(newRec->productId, id);  
    newRec->productPrice=atoi (priceChar);  

    if (fprintf(DynsaleDayPtr,"%d %s %s %d", strlen(newRec->productName),  
    newRec->productId, newRec->productName, newRec->productPrice)>0)  
    {  
        *dynNumOfRecords=(*dynNumOfRecords)+1;  
        return True;  
    }  
}

thanks!

Upvotes: 0

Views: 3403

Answers (4)

Philip
Philip

Reputation: 5917

fprintf() most likely uses buffered output. Therefore, you should either fflush() the DynSaleDayPtr stream or, better yet, print a newline to the file. The latter has the added benefit of making the file contents actually readable...

Also, don't forget to close() the stream when you're finished with writing. This will also render fflush() unnecessary.

Upvotes: 0

Prince John Wesley
Prince John Wesley

Reputation: 63688

You need to flush the stream.

fflush(FILE*);

Of course, you have to close the stream if you have done with it.

fclose(FILE*);

Upvotes: 1

AndersK
AndersK

Reputation: 36082

A thought:

scanf("%s%s%s",id,name,priceChar);

the above statement is a bit dodgy since you haven't said how many bytes should go in each string.

better to use fgets() then parse the string retrieving the individual values or create a better format specifier.

If the above statement causes a memory overwrite the rest of your program could malfunction causing things like what you describe.

Upvotes: 0

Jeff
Jeff

Reputation: 2009

Agree with @pmg - try something like this:

FILE *pFile = fopen("foo.txt","w");
if (pFile==NULL)
   bad();
fprintf(pfile,"Hello world\n");
fclose(pfile);

make that work first - then fix whatever's wrong in the big app -

Upvotes: 0

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