C write struct to file - c

Question

I am trying to save struct data to file. I saved the data this way.
node_trx * trx_list;
trx_list = calloc(1, sizeof(node_trx *));
trx_list->amount = "123123123";
trx_list->currency = 123;
trx_list->next_node = NULL;
if (1 != fwrite(trx_list, length, 1, f)) {
//error
}
free(trx_list);
Here is my struct:
typedef struct {
char amount;
int currency;
struct node_trx * next_node; } node_trx;
Main problem is after i saved struct to file and then after read, when print values, it is printing wrong values. For example: i stored currency as 123, then printed 6788576 this kind of numbers.
here is my reading code:
int read_last_trx_from_file (const char * file_name, node_trx * * trx, unsigned * trx_len)
{
FILE * f;
*trx = NULL;
if (NULL == (f = fopen(tools_get_full_filename_const(file_name), "rb")))
{
return 2; //error
}
size_t fsize;
fseek(f, 0, SEEK_END);
fsize = ftell(f);
fprintf(stdout, "file size: %zd\n", fsize);
if (!fsize)
{
fclose(f);
return 3; //no data
} else {
if (fsize == 1) {
return 3; // no data
}
}
rewind(f);
if (NULL != (*trx = (node_trx *) calloc(1, fsize)))
{
if (1 != fread(*trx, fsize, 1, f))
{
fclose(f);
free(*trx);
return 2; //error
}
}
fclose(f);
*trx_len = fsize;
return 0; //OK }
Main function that calls read function:
int display_trx() {
node_trx * card_data;
if (3 != read_last_trx_from_file(LAST_TRX_OBJECT, &card_data, &data_set_len)) {
if (card_data != NULL) {
printf("%s AMOUNT \n", card_data->amount);
printf("%d CURRENCY \n", &card_data->currency);
}
}
}
After i read this way , when i print amount data, segmentation fault error occurs. so why segment error occured?
And when i print currency, it printing 734364636 this kinda numbers. So why it prints wrong numbers.
Or i only wrote pointer of struct to file?
Please help me guys.

Answer 1

There are two obvious errors in your code.
In struct declaration, the type of amount is char, but when you initialize it in trx_list->amount = "123123123";, you assigned a string, or char[10] array (there is an extra one for NULL terminator).
In function display_trx, second printf, the result of &card_data->currency is int *, not int. If you want to print out currency, why don't follow the first print, use card_data->currency (without &)? You get that large number because you are printing pointer value implicitly converted into int, or the address of currency in card_data.
And there is one error which compiler will not warn you (because it is not syntactically wrong.). As BLUEPIXY said in the comments, when allocating and initializing trx_list, you should really use calloc(1, sizeof(node_trx)). You are allocating space for what pointer trx_list points to, not the pointer itself, so there should not be an asterisk in sizeof.
My suggestion is using a "smart" compiler, such as gcc, and enable warnings. This is a good practice (at least for me). Thank you!