CODEWITHSUNDEEP
ciofread
user1889966
user1889966

Reputation: 165

Reading from file to array

I am trying to read from a file. I am using fread(), but I'm unsure whether I'm going about this correctly. I want to create an array of structs and continue "f-reading" from the file into the array like so:

//Get size of file
struct stat st;
stat(document, &st);
int size = st.st_size;

//Create appropriate array size of structs

struct Person person[size];

for(j = 0; j < size; j++) {
    fread(person[j].name, 1, 16, fp); //each name is truncated to 15 bytes on the file
    fread(person[j].text, 1, 24, fp);  //text is truncated to 24 on the file
}

struct Person look like so:

struct Person {
    char name[16];
    char text[24];
};

Am I using fread() correctly? Thank you.

Upvotes: 1

Views: 145

Answers (3)

Deepu
Deepu

Reputation: 7610

The code given below is sufficient inside the for loop

fread(person[j], sizeof(struct Person), 1, fp);

Upvotes: 1

JRK
JRK

Reputation: 182

Increment j by sizeof(struct Person) to avoid fread issue Alternatively you can use feof to check end of file

Upvotes: 0

Shantanu
Shantanu

Reputation: 383

You should check if the fread function call succeeded in reading the expected number of bytes from the data stream:

//Get size of file
struct stat st;
int name_bytes_read, text_bytes_read; // If using C11, use size_t instead
stat(document, &st);
int size = st.st_size;


//Create appropriate array size of structs

struct Person person[size];

for(j = 0; j < size; j++) {
    name_bytes_read = fread(person[j].name, 1, 16, fp); //each name is truncated to 15 bytes on the file
    if (name_bytes_read != 16) { 
      fputs ("Error reading name record", stderr); 
      exit(-1);
    }
    text_bytes_read = fread(person[j].text, 1, 24, fp);  //text is truncated to 24 on the file
    if (text_bytes_read != 24) {
      fputs ("Error reading text record", stderr);
      exit(-1); }
}

Further reading: http://www.thegeekstuff.com/2012/07/c-file-handling

Upvotes: 0

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