我需要将文件“Mus​​icLibrary.txt”中的数据复制到结构。 但是当我使用我的代码时，它不会返回任何内容

Question

Here's my code for copying the file.

song_t *ReadFile(song_t *head){
FILE *input;
input = fopen("MusicLibrary.txt", "r");
song_t *temp = head;
string title;
string artist;
string album;
string genre;
string store;
string buffer;

while(fgets(buffer, MAXSIZE, input) != NULL){
    temp = (song_t *)malloc(sizeof(song_t));
    fgets(temp->title, MAXSIZE, input);
    fgets(temp->artist, MAXSIZE, input);
    fgets(temp->album, MAXSIZE, input);
    fgets(temp->genre, MAXSIZE, input);
    fgets(store, MAXSIZE, input);
    temp->rating = atof(store);
    temp->next == NULL;
    temp = temp->next;
}

fclose(input);
return head;
}

and here is the code for my structre:

typedef struct song{
string title;
string artist;
string album;
string genre;
float rating;
struct song *next;
}song_t;

also, typedef char string[30];

i can't seem to copy the data from files to the structure in main. Can anyone help me with this?

Answer 1

while(fgets(buffer, MAXSIZE, input) != NULL){
    temp = (song_t *)malloc(sizeof(song_t));
    fgets(temp->title, MAXSIZE, input);
    fgets(temp->artist, MAXSIZE, input);
    fgets(temp->album, MAXSIZE, input);
    fgets(temp->genre, MAXSIZE, input);
    fgets(store, MAXSIZE, input);
    temp->rating = atof(store);
    temp->next == NULL;
    temp = temp->next;
}

There are a few problems with the above code that may not be problems depending on you input file format, but here goes:

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First, you control the while loop with a fgets that throws a line away. Are you certain that's what you wanted.

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Secondly, you should always check the return value from malloc in case it fails.

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Thirdly, you're assuming that each field is on its own line. You should confirm that.

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Fourth, you're not really inserting correctly into a linked list. If your intent is to insert new items at the start of the list, change:

temp->next == NULL;
temp = temp->next;

into:

temp->next == head;
head = temp;

and ensure you call it as:

actualHead = ReadFile (actualHead);

to update the head pointer correctly.

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