Writing and printing strings from an array in a file in C

Question

I have an array being written to the file, but then I need a way to print that same information out from the file when I call the function. The first part of the code is in the main function, and the second is a second function that prints out the values that are supposed to be from the file (fp).

fp = fopen("Grue.txt", "wb");
for(i = 0; i < 5; i++)
{
    char newLine[3] = {"\n"};
    char space[2] = {" "};
    fwrite(array[i].name, strlen(array[i].name), sizeof(char), fp);
    fwrite(space, strlen(space), sizeof(char), fp);
    fwrite(array[i].height, strlen(array[i].height), sizeof(char), fp);
    fwrite(space, strlen(space), sizeof(char), fp);
    fwrite(array[i].weight, strlen(array[i].weight), sizeof(char), fp);
    fwrite(space, strlen(space), sizeof(char), fp);
    fwrite(array[i].items, strlen(array[i].items), sizeof(char), fp);
    fwrite(newLine, strlen(newLine), sizeof(char), fp);
}
fclose(fp);
fp = fopen("Grue.txt", "rb");
PrintAGrue(fp);


void PrintAGrue(FILE *a)
{
 // create End of file character onto the array being saved,
int i;
char n;
char h;
char w;
char m;

for (i=0; i<5; i++)
{
     n = fread(a[i].name,  strlen(array[i].name, sizeof(char), a);
     h = fread(array[i].height,  strlen(array[i].height, sizeof(char), a);
     w = fread(array[i].weight,  strlen(array[i].weight, sizeof(char), a);
     m = fread(array[i].items,  strlen(array[i].items, sizeof(char), a);

     printf("This grue is called %s and is %s feet tall, and weighs %s pounds, and has eaten %s things.", n, h, w, m);
}

}

So what does it do when you try this?

Charlie Martin
– Charlie Martin

2012-04-19 21:47:03 +00:00
Commented Apr 19, 2012 at 21:47 — Charlie Martin
– Charlie Martin, Commented Apr 19, 2012 at 21:47

Jim Lewis · Accepted Answer · 2012-04-19 21:53:14Z

1

In PrintAGrue, it looks like you're using strlen() calls to decide how much data to read -- but how can you know the size of the string before you've read it? (Also, the parentheses don't look balanced...)

Perhaps your file format should explicitly include a length field for each string -- then you can do one fread to find the string size, and another to actually read the string.

answered Apr 19, 2012 at 21:53

Jim Lewis

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