Loading a text file into a struct using C - c

Question

I try to load the contents of a text file into a structure.
My idea looks like this:
I have two files, struct.h , main.c and a list.txt file .
in file struct.h :
struct analg {
char word[6];
char signature[6];
};
struct analg h[106];
FILE *fp;
In file main.c :
#include<stdio.h>
#include "struct.h"
void load() {
fp = fopen("list.txt", "r");
if(fp == NULL) {
printf("fail");
return 1;
}
else {
printf("file loaded!\n");
}
fclose(fp);
return;
}
void print() {
int i;
for(i=0; i<1000; i++) {
while(fgets(h[i].word, 6, fp)) {
printf("%s", h[i].word);
}
}
return;
}
int main () {
int choice;
do {
printf("choose L or P: ");
scanf("%s", &choice);
switch(choice) {
case 'l':
load();
printf("\n[l]oad - [p]rint\n");
break;
case 'p':
print();
printf("\n[l]oad - [p]rint\n");
break;
default:
break;
}
} while(choice!='q');
return;
}
In file list.txt :
throw
timer
tones
tower
trace
trade
tread
So I try to load the text file by pressing the "L" to the structure, and then when I press the 'p' will be displayed, but it is not!

Answer 1

In your code, I see there are 2 potential issues. The choice has to be a character to be switched based on l or p. You may have to add cases to handle the upper case also.
Another issue is that in load function, you are closing the file pointer. Hence, when you enter the print function fgets may not work as the fp is already closed.
To load your file into structure, the load has to be modified as
void load() {
fp = fopen("list.txt", "r");
if(fp == NULL) {
printf("fail");
return; // There was an error in original code as this was returning 1
}
do{
fgets(h[count++].word, 6, fp); // Count is a global variable - no. of elements read
}while(!feof(fp));
printf("file loaded!\n");
fclose(fp);
return;
}
The corresponding print function would become
void print(){
int i;
printf("Inside print\n");
for(i=0; i < count; i++) {
printf("%s", h[i].word);
}
return;
}
the main function would be,
int main (){
char choice;
do{
printf("choose L or P: ");
scanf("%c", &choice); //Only character is read and hence, %s is not required
switch(choice){
case 'l':
load();
printf("\n[l]oad - [p]rint\n");
break;
case 'p':
print();
printf("\n[l]oad - [p]rint\n");
break;
default:
case 'q':
break;
}
} while(choice !='q');
return 0;
}
One last point. In the scanf statement if scanf("%s", &choice); is employed, then a runtime check error is generated when main exits, with a message that stack is corrupted around the variable choice.

Answer 2

I'll comment up what your code is doing:
void load() {
fp = fopen("list.txt", "r"); // opens the file for reading
if(fp == NULL) {
printf("fail"); // if the file couldn't be opened, return an error
return 1; // (aside: a void function can't return an int)
}
else {
printf("file loaded!\n"); // tell the user that the file was opened
}
fclose(fp); // close the file, having read nothing from it
return;
}
At no point do you read anything from the file. What you have in memory will therefore have no relation to whatever you have on disk.
C has no built-in means for serialising and deserialising structs so what you need to do is define a formal grammar for your file on disk and write code that can parse that grammar into your structs.