从文件读取数据并读入结构

Question

I'm trying to read in data from a file and store the data in a struct. The struct looks like this:

struct someData {
    int number;
    char *name;
};

The data in the file can be any format. Right now I'm trying to just read in CSV format. The data will always be a string followed by an integer.

some string data,100
another string,500

Here is the part of the code where I'm trying to read the data and place it in the struct.

FILE *ifp;
char *mode = "r";
char *name;
int number;

ifp = fopen("myDataFile.txt", mode);

if (ifp == NULL) {
    fprintf(stderr, "Can't open input file in.list!\n");
    exit(1);
}

// read up to 100 characters up to a comma, then a decimal
while(fscanf(ifp, "%100[^,],%d\n", name, &number) != EOF){ 

    // print out the data we got 
    printf("Data from file:  %s  %d", name, number);


    struct someData *newData = (struct someData *) malloc(sizeof(struct someData));
    newData->number = number;
    newData->name = name;
    printf("Name: %s  Number: %d\n\n",newData->name, newData->number);
    } 

The print statements give me the following

Data from file: some string d 100
Name: some string d  Number: 100

Data from file: another stri  Number: 500
Name: another stri  Number 500

The second name gets cut off and actually ends up printing a couple of weird characters. I think something is wrong with my fscanf in the while loop. I've tried a few other ways to get the data like using %s instead of %100 but nothing is working.

Answer 1

You need to change the second char *name; to char name[101]; (not the one in the struct ).

And it would be better if you changed:

    while(fscanf(ifp, "%100[^,],%d\n", name, &number) != EOF){

to

    while(fscanf(ifp, " %100[^,],%d", name, &number) == 2){

This:

• Adds skipover of initial white space
• Removes trailing \\n , which can sometime cause problems
• Verifies that two valid arguments have been read.

Also newData->name = name; won't work: you'll need something like newData->name = strdup(name); .

Also, as a matter of style, I would suggest changing:

     struct someData *newData = (struct someData *) malloc(sizeof(struct someData));

to:

     struct someData *newData = malloc(sizeof *newData);

which will avoid some redundancy ie "DRY".

And you never save newData ; I presume you are planning to add it to a linked-list or some other such container.

Also, you'll eventually need to add error-checking, but that is beyond the scope of this question.

Answer 2

You are using not-initialised pointer node. The function fscanf requires for strings some buffer, and you do not provide any.