load file content into structure only if file exists or use default values

Question

I have the following code:

typedef struct my_data {
 char* name;
}my_data;

my_data data[]={
    { .name = "Peter" },
    { .name = "James" },
    { .name = "John" },
    { .name = "Mike" }
};


void loaddata()
{
    FILE * in;
    if((in = fopen("data.txt","rt")) != NULL) {
        printf("start loading\n");
        int i = 0;
        while(!feof(in))
        {
            fscanf(in,"%s", &data[i].name);
            printf("%s\n",data[i].name);
            i++;
        };
    }
    else
        printf("loading not required\n");
    fclose(in);
}

And it gives me a "killed" error.

How can I load data from file data.txt into existing structure and in case file doesn't exist to use default values which were defined ?

Oleg Olivson · Accepted Answer · 2013-09-20T13:39:06.633

1

No need "&" in:

fscanf(in,"%s", &data[i].name);

and no need to close filestream if it's not opened.

void loaddata()
{
    FILE * in;
    if((in = fopen("data.txt","rt")) != NULL) {
        printf("start loading\n");
        int i = 0;
        while(!feof(in))
        {
            fscanf(in,"%s", data[i].name);
            printf("%s\n",data[i].name);
            i++;
        };
        fclose(in); /* need closing */
    }
    else
        printf("loading not required\n");
    /* no need closing */
}

UPD: create structure with allocated memory, not pointer. Pointer accesses part of program, not memory, so you cannot save data there.

typedef struct my_data {
    char name[10];
}my_data;

edited Sep 20 '13 at 13:39

answered Sep 20 '13 at 12:41

Oleg Olivson

489
2
5

w\o & I get Segmentation fault – Sam Reina Sep 20 '13 at 12:49
move close(in); into if{ } – Oleg Olivson Sep 20 '13 at 12:51
I'm using an older version of gcc, but the program must compatible with any, right? – Sam Reina Sep 20 '13 at 13:04
Sorry, "killed" error was caused misplaced close(). fscanf(in,"%s", &data[i].name); use is correct. Also, use temporary vaiable between reading from file and saving to structure. – Oleg Olivson Sep 20 '13 at 13:13
I still get that killed error if file exists, otherwise it's working – Sam Reina Sep 20 '13 at 13:21
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/37738/discussion-between-oleg-olivson-and-sam-reina) – Oleg Olivson Sep 20 '13 at 13:24
yes, you're right, I forgot to modify that. now it's working. glad you noticed that :) – Sam Reina Sep 20 '13 at 14:41
I have another issue now, with the array size. If the number of lines in file is less than those in the defined array list I get a lot of empty elements. – Sam Reina Sep 20 '13 at 15:32
[count lines of a file](http://stackoverflow.com/questions/4278845/count-the-lines-of-a-file-in-c) – Oleg Olivson Sep 23 '13 at 06:12

load file content into structure only if file exists or use default values

1 Answers1