Thread: Random access files and structures

Right now I'm trying to read in a buncho f data from the text file "Top_Movies.txt" and putting the data into a structure. This is what I have so far. Now I know it isn't goign to work so I'm not even going to bother trying to compile it...but am I even close? I think I am but what do I know? I've also included the text file, which I do not know how to include in the actual program:

Code:

#include <stdio.h>


struct Movies {
	int rank;
	float rating;
	char title[25];
	char director[25];
};

int main()
{
	struct Movies list[50];
	int ranking;
	float rate;
	char movie[25];
	char bywhom[25];
	int i;
	
	
	FILE *myFile;

	myFile = fopen("Top_Movies.txt", "r");
		if (myFile == NULL) {
			printf("Unable to open Top_Movies.txt.\n");
		
		else
		{ for (i=0;i<50;i++)
			{
				fscanf( myFile, "%d%.1f%c%c", &ranking, &rate, movie, bywhom);
				
				list[i].rank = ranking;
				list[i].rating = rate;
				list[i].title = movie;
				list[i].director = bywhom;
		}
		} 
		
		fclose(myFile);
		return 0;


		}

here's the txt file:

1, 9.1, The_Godfather, 1972, Francis_Ford_Coppola
2, 9, The_Shawshank_Redemption, 1994, Frank_Darabont
3, 8.9, The_Godfather:_Part_II, 1974, Francis_Ford_Coppola
4, 8.8, The_Lord_of_the_Rings:_The_Return_of_the_King_, 2003, Peter_Jackson
5, 8.8, Shichinin_no_samurai, 1954, Akira_Kurosawa
6, 8.8, Schindler's_List, 1993, Steven_Spielberg
7, 8.7, Casablanca, 1942, Michael_Curtiz
8, 8.7, Star_Wars:_Episode_V_-_The_Empire_Strikes_Back, 1980, Irvin_Kershner
9, 8.7, Pulp_Fiction, 1994, Quentin_Tarantino
10, 8.7, Star_Wars, 1977, George_Lucas
11, 8.7, Il_Buono_il_brutto_il_cattivo, 1966, Sergio_Leone
12, 8.7, One_Flew_Over_the_Cuckoo's_Nest, 1975, Milos_Forman
13, 8.7, The_Lord_of_the_Rings:_The_Fellowship_of_the_Ring, 2001, Peter_Jackson
14, 8.7, Rear_Window, 1954, Alfred_Hitchcock
15, 8.6, Cidade_de_Deus, 2002, Fernando_Meirelles
16, 8.6, The_Usual_Suspects, 1995, Bryan_Singer
17, 8.6, The_Lord_of_the_Rings:_The_Two_Towers, 2002, Peter_Jackson
18, 8.6, Raiders_of_the_Lost_Ark, 1981, Steven_Spielberg
19, 8.6, 12_Angry_Men, 1957, Sidney_Lumet
20, 8.6, Dr._Strangelove_or:_How_I_Learned_to_Stop_Worrying _and_Love_the_Bomb, 1964, Stanley_Kubrick
21, 8.6, Citizen_Kane, 1941, Orson_Welles
22, 8.6, Memento, 2000, Christopher_Nolan
23, 8.6, Psycho, 1960, Alfred_Hitchcock
24, 8.6, Goodfellas, 1990, Martin_Scorsese
25, 8.6, C'era_una_volta_il_West, 1968, Sergio_Leone
26, 8.5, North_by_Northwest, 1959, Alfred_Hitchcock
27, 8.5, The_Silence_of_the_Lambs, 1991, Jonathan_Demme
28, 8.5, Lawrence_of_Arabia, 1962, David_Lean
29, 8.5, Le_Fabuleux_destin_d'Amelie_Poulain, 2001, Jean-Pierre_Jeunet
30, 8.5, It's_a_Wonderful_Life, 1946, Frank_Capra
31, 8.5, Sunset_Blvd., 1950, Billy_Wilder
32, 8.5, Fight_Club, 1999, David_Fincher
33, 8.5, American_Beauty, 1999, Sam_Mendes
34, 8.4, The_Matrix, 1999, Andy_Wachowski/Larry_Wachowski
35, 8.4, Vertigo, 1958, Alfred_Hitchcock
36, 8.4, Eternal_Sunshine_of_the_Spotless_Mind, 2004, Michel_Gondry
37, 8.4, Taxi_Driver, 1976, Martin_Scorsese
38, 8.4, Apocalypse_Now, 1979, Francis_Ford_Coppola
39, 8.4, Paths_of_Glory, 1957, Stanley_Kubrick
40, 8.4, To_Kill_a_Mockingbird, 1962, Robert_Mulligan
41, 8.4, Der_Untergang, 2004, Oliver_Hirschbiegel
42, 8.4, Se7en, 1995, David_Fincher
43, 8.4, The_Pianist, 2002, Roman_Polanski
44, 8.4, Chinatown, 1974, Roman_Polanski
45, 8.4, Leon, 1994, Luc_Besson
46, 8.4, Sen_to_Chihiro_no_kamikakushi, 2001, Hayao_Miyazaki
47, 8.4, Hotel_Rwanda, 2004, Terry_George
48, 8.4, American_History_X, 1998, Tony_Kaye
49, 8.3, The_Third_Man, 1949, Carol_Reed
50, 8.3, Monty_Python_and_the_Holy_Grail, 1975, Terry_Gilliam/Terry_Jones

>> if (myFile == NULL)

if the file pointer is null, be sure not to fclose on it.

>> for (i=0;i,50;i++)

always inspect your code for typos and *do* try to compile it.

>> fscanf( myFile, "%d%.1f%c%c", &ranking, &rate, movie, bywhom);

%c is for single characters, you'll want %s to get a string. you'll also need to skip all that punctuation, fscanf has format specifiers for that too but unfortunately, I never use the function so I can't remember the exact format (maybe search the board).

>> list[i].title = movie;

you can't assign arrays like that in C - use strcpy, strncpy, or memcpy for that. better yet, pass the struct members directly to fscanf and save yourself some trouble.

also, you should always check the return value of fscanf.

1, 9.1, The_Godfather, 1972, Francis_Ford_Coppola

Code:

struct Movies {
	int rank;
	float rating;
	char title[25];
                char year[6];
	char director[25];
};

need to read the year as well from the file and store it in the structure/container

ssharish2005

Originally Posted by ssharish2005

need to read the year as well from the file and store it in the structure/container

ssharish2005

can't I use int year?
this is what I have so far. I have the printf statement at the bottom just to see if it works (which it doesn't). I can't figure out any way to fix it. I also get a warning "warning C4013: 'strncpy' undefined; assuming extern returning int
Linking..."

Code:

#include <stdio.h>


struct Movies {
	int rank;
	float rating;
	char title[25];
	int year;
	char director[25];
};

int main()
{
	struct Movies list[50];
	int ranking;
	float rate;
	int theyear;
	char movie[25];
	char bywhom[25];
	int i;
	
	
	FILE *myFile;

	myFile = fopen("Top_Movies.txt", "r");
		if (myFile == NULL) {
			printf("Unable to open Top_Movies.txt.\n");
			return (-1);
		}
		while (!feof(myFile)) {
			for (i=0;i<50;i++)
			{
				fscanf( myFile, "%d%.1f%d%s%s", &ranking, &rate, &theyear, movie, bywhom);
				
				list[i].rank = ranking;
				list[i].rating = rate;
				list[i].year = theyear;
				
				strcpy (list[i].title, movie);
				strcpy (list[i].director, bywhom);
				
				printf("%s", list[i].title);
		
		} 
		}
	
		return (0);


		}

Title never gets set because fscanf fails before it gets to that point.
Your format string does not match your input.

1, 9.1, The_Godfather, 1972, Francis_Ford_Coppola

For example you have to take into account the commas
(don't use %.1f for input just %f)

Code:

fscanf( myFile, "%d,%f,%d,%s,%s", &ranking, &rate, &theyear, movie, bywhom);  //Just an example.

Also, it looks like it should be

Code:

int, float, string, int, string

That's not what you have.


You should check that fscanf returned the number of elements you expected, and print an error if it didn't.

Code:

if(fscanf(...) != 5) {
  //failed to parse the line
}

Finally, because of the parse failure you are getting into an infinite loop. You never get to the end of the file.
The FAQ has an entry on why it is bad to use feof to control a loop.
Better to use fgets then parse the line with sscanf.

example:

Code:

    char line[80];

    //loop through each line in the file
    while (fgets(line, sizeof(line), myFile)) {
        //Things to do...
        //-Make sure sscanf returned the correct count
        //-Fix the format string to match my input
        //-flose my file when done (outside of loop)
        //-Do I need these temporary variables? why not just read into list[i].rank etc.

        sscanf( line, "%d,%f%d%s%s", &ranking, &rate, &theyear, movie, bywhom);

        list[i].rank = ranking;
        list[i].rating = rate;
        list[i].year = theyear;

        strcpy (list[i].title, movie);
        strcpy (list[i].director, bywhom);
        i++;
    }

The FAQ has an entry on why it is bad to use feof to control a loop.

http://faq.cprogramming.com/cgi-bin/...&id=1043284351
http://faq.cprogramming.com/cgi-bin/...&id=1043284351