Structures and Arrays

[w274v]

Hey,

I've read the tutorials on structs and arrays, and my program needs to be much like this piece below...

struct Person {
  char *name;
  int age;
  float height;
} people[] = {
  {"Prelude", 25, 5.9f},
  {"Generic person", 20, 6.0f}
};

...except my program scans in the name/age/height from a file instead of typing it in. How can I scan this in?

[Richie T]

http://www.cprogramming.com/tutorial/cfileio.html

this should get you started

[Dave_Sinkula]

First, I'd make name and people into arrays (unless you also want to deal with dynamic allocation). Then I'd take a look at the file format, but likely use some form of fgets/sscanf to read the data.

[filker0]

Write a function that reads the name/age/height into a structure pointed to by one of its paramaters. You'll have to come up with some way to store the name, as the struct you list uses a pointer to char, and each copy of the struct will have its own name. You can do something like:

/* assume the local variables:
 *   int newAge;  // contains the age read from the file
 *   float newHeight; // contains the height read from the file
 *   char newName[MAXLEN]; // contains the name read from the file
 *   struct Person *newPerson; // contains a pointer to the array element to be filled in
 */
char *nBuff = malloc(strlen(newName)+1);
if (nBuff == NULL)
{
    /* Can't allocate a name, abort or handle the error some other way */
}
else
{
    strcpy(nBuff, newName);
    newPerson->name = nBuff;
    newPerson->age = newAge;
    newPerson->height = newHeight;
}

Call the function with a pointer to each successive element until you reach the end of your file. When you're done, you should remember to call free() on the name member of each array entry you read in, otherwise you'll have a memory leak.

Note: I know that this can be coded in fewer steps/more efficiently, but I'm trying to be as clear as possible here.

[w274v]

So is there no way to do something like this:

struct Person {
  char *name;
  int age;
  float height;
} people[] = {
  {"fscanf(inp, "%s", &people[1])", fscanf(inp, "%s", &people[2]), fscanf(inp, "%s", &people[3])},
};

[Dave_Sinkula]

There are ways, but certainly not some nice, easy one-liner.