Read file into typedef struct that includes an enum in C?

I am having trouble reading in a file into a typedef struct that includes an enum. I am a beginner in C, so I don't really know how to read in the file with the enum.

I am able to read the file and print out the contents in simple code, but I need to read the file in and assign each string in the line into the type from the typedef struct.

The input file ooks like this:

random.num year model category
Example:
54 2012 model1 type1

These are the relevant parts of my code:

typedef enum { type1, type2, type3, type4} category;

typedef struct {
        int num;
        int year;
        char make[MAX_MAKE_CHARS];
        category category;  //enum from above
}item; 

//reading in the file I have this:

int create_db(char *f){

char file_contents[100];                                                                                                               // read the file --> ("r")                                                                                                             FILE *f = fopen(f, "r");
                                                                                                                                               // check if file can be used
if(f == NULL){ 
      printf("File not found");
      exit(1);
}
                                                                                                                                               int i = 0;                                                                                                                             item item_array[100];
while(fscanf(f, "%d %d %s %s", &item[i].num, &item[i].year, item[i].make, item[i].category) != EOF){ 
         // can't get past the while look where it says "item[i].category

I get the error:

format ‘%s’ expects argument of type ‘char *’, but argument 6 has type ‘category * {aka enum *}’

Since I am completely new to C, I am confused on how to read in the file into a struct. What do I do for the item[i].category?

Solution

Unfortunately an enum is a symbol that is valid only in the code, and there's no way to access this symbol at runtime as a string. Any enum variable is actually stored as an integer

But there is something you can do:

Define an array of char * containing the symbols of the enum as strings
Store the enum symbol contained in the input file within a temporary string
Check the return value of scanf
Call an utility function searching the temporary string within the constant array of strings and returning the corresponding enum value
If the string is not found raise an error
If the string is found, store the enum value within your output struct

In the following example code I omit your while for clarity (you will be able to add it back according to your requirements not described in the question):

int tmp_num;
int tmp_year;
char tmp_make[100];
char tmp_category_str[10]; // <-- define the size according to the max enum symbol length

if(fscanf(f, "%d %d %99s %9s", &tmp_num, &tmp_year, tmp_make, tmp_category_str) == 4)
{
    int tmp_category;
    if( ( tmp_category = check_enum( tmp_category_str ) ) != -1 )
    {
        Item.num  = tmp_num;
        Item.year = tmp_year;
        strcpy( make, tmp_make );
        Item.category = ( category )tmp_category; // The numeric value is stored in the struct
    }
    else
    {
        printf( "Invalid 'category' value!\n" );
    }
}

Note that:

I expect the return value of fscanf to be 4
I changed make size to 100. The purpose is showing in a simple way that the format specifier %s should contain the limit to arr_size-1 characters, for safety
The check_enum() will return -1 if a strange string value, not matching any enum symbol, is provided

Now, only check_enum() implementation is missing. Just loop on enumSymbols[] elements searching for the input string.

char* enumSymbols[] = { "type1", "type2", "type3", "type4" };

int check_enum(char * str)
{
    int ret = -1;
    
    if( str )
    {
        for( int i=0; i<(sizeof(enumSymbols)/sizeof(enumSymbols[0])); i++ )
        {
          if( strcmp(enumSymbols[i], str) == 0 )
          {
              ret = i;
              break;
          }
        }
    }

    return ret;
}

Note: this works but you'll have to keep the array and the enum aligned. In order to prevent human alignment mistakes, a solution like this one can be implemented. In this answer I explain how to create an aligned enum/struct pair, but in the same way and using the preprocessor stringifier operator # also an aligned enum/string array pair can be generated.