Thread: Reading Data From File to Linked List

The data from the text file looks like:
40T Trapp, Dave; 3.9
pin# Last_Name, First_Name; gpa

I am trying to read them into a linked list composed of the structure:

Code:

typedef struct
{
    char pin[4];
    char *name;
    double gpa;
}   STU;

So far the function I used to read the data from the file worked successfully for my test file which was only contained integers and placed them into a sorted linked list.
My only concern now is modifying it to accommodate the data I need.
I was told that I should use fgets and sscanf but I am not too certain of how to go about doing this, especially since we only covered sscanf very briefly so I am still not very sure of what it does and I can't find very clear examples online.
Here's the original function:

Code:

int getData (FILE* fpData, STU* pData)
{
    int ioResult;

    ioResult = fscanf (fpData, "%d ", pData->test);
    if (ioResult == 1)
       return 1;
    else
       return 0;
}    // getData

I am calling it inside of a larger function which builds the sorted list.

Any and all feedback is appreciated

sscanf() works just like scanf(), except you add one parameter, which is the name of the char array you are scanning, first:

fgets() is a lovely way to get a row of text:

Code:

sscanf(filePointerName, "%YourFormatSpecifierHere",&AddressOfYourVariableReceivingTheValue); //&number (or arrayName with no &)
fgets(charArrayName, sizeof(charArrayName), filePointerName);

The trick is to always keep a larger than you ever will need array size, (waste a tiny bit of memory to keep everything running well), and you will have a newline ('\n') and an end of string char, added to your char array[].

So here's how I've implemented it thus far:

Code:

int getData (FILE* fpData, STU* pData)
{
//    Local Definitions
    int ioResult;
    char temp[MAX_SIZE];

//    Statements
    fgets(temp, sizeof(temp), fpData);
    sscanf(temp, "%4s", pData->pin);
    sscanf(temp + sizeof(pData->pin), "%[^;]", pData->name);
    sscanf(temp + sizeof(pData->name), "%lf", pData->gpa);
    printf("%s pin :%s name :%s gpa:%4.2lf\n", temp, pData->pin, pData->name, pData->gpa);
    ioResult = 1;
    system("pause");
    if (ioResult == 1)
       return 1;
    else
       return 0;
}    // getData

It successfully scans in the pin and the name, albeit it without the semi-colon at the end. It seems that doing this screws up the data that comes afterward because when I try to print the gpa it gives me a bunch of garbage.

How big is MAX_SIZE ... your input data is probably being clipped, make the buffer bigger...

The usual technique is to make your buffer bigger than you'll ever need for a single line... If your file has lines that are (for example) 80 char max... make your buffer 128 bytes.

MAX_SIZE is initialized to 1000..

I know I need to make some more changes because I also need to dynamically allocate memory for the names before I initialize them

K so I managed to successfully get all the data I wanted into the structure

Code:

int getData (FILE* fpData, STU* pData)
{
//    Local Definitions
    int ioResult;
    char temp[MAX_SIZE];
    char *pGpa, *pEnd, *pName;

//    Statements
    fgets(temp, sizeof(temp), fpData);

    sscanf(temp, "%4s", pData->pin);

    pGpa = strrchr(temp, ';') + 1;
    pData->gpa = strtod(pGpa, &pEnd);

    *pGpa = '\0';
    pName = temp + sizeof(pData->pin);
    pData->name = (char *)calloc (strlen(pName) + 1, sizeof(char));
    if(!pData->name)
        printf("Error! Out of memory\n");
    strcpy(pData->name, pName);

    printf("%s %s %.2lf\n", pData->pin, pData->name, pData->gpa);
    ioResult = 1;
    system("pause");
    if (ioResult == 1)
       return 1;
    else
       return 0;
}    // getData

Don't know if there is an easier way to do this...