CODEWITHSUNDEEP
c
Intelwalk
Intelwalk

Reputation: 671

C Read until end of file

I currently have code that reads 4 lines and I want to be able to change that until EOF or my MAX const int value. I can not get the !EOF to work right and was wondering how would I change my code to accomplish this?

Thanks in advance

#include <stdio.h>

struct record{
    char name[2];
    int arrival_time;
    int job_length;
    int job_priority;
};

const int MAX = 40;

int main(void)
{
    struct record jobs[MAX];
    int i = 0;
    int j;
    FILE *f = fopen("data.dat","rb");

    while (fscanf(f, "%s %d %d %d", &jobs[i].name, &jobs[i].arrival_time,
                  &jobs[i].job_length, &jobs[i].job_priority) == 4 && i < MAX)
      i++;

    for (j = 0; j < i; j++)
        printf("%s %d %d %d\n", jobs[j].name, jobs[j].arrival_time,
               jobs[j].job_length, jobs[j].job_priority);

    fclose(f);

    return(0);
}

Upvotes: 5

Views: 84681

Answers (4)

Riccardo Scorretti
Riccardo Scorretti

Reputation: 13

Personnaly, I would code like this:

for(i=0 ; i<MAX ; ++i) {
    fscanf(f, "%s %d %d %d", &jobs[i].name, &jobs[i].arrival_time,
           &jobs[i].job_length, &jobs[i].job_priority);
    if(ferror(f)  ||  feof(f)) break;
}

The key point is that, at the best of my knowledge, you cannot know that a file is come to end without trying to read it. That is the reason why I check feof() and ferror() after having read data. At the end of the loop, the variable i contains the number of read data

Upvotes: 1

Martin Beckett
Martin Beckett

Reputation: 96109

Something like

while (fscanf(f, "   %s   ", &etc) != EOF) {

}

Then use feof(f) to check if it was a fscanf error or actually EOF.

Upvotes: 8

caf
caf

Reputation: 239041

You need to change the order of the tests in your while() loop - you must test i < MAX before calling fscanf(), or else you'll potentially call it one too many times (you should also be passing jobs[i].name without the & to fscanf):

while (i < MAX && fscanf(f, "%s %d %d %d", jobs[i].name, &jobs[i].arrival_time,
              &jobs[i].job_length, &jobs[i].job_priority) == 4)

Upvotes: 1

Piotr Praszmo
Piotr Praszmo

Reputation: 18320

Your code seems to do what you want, except:

char name[2];

Names will probably be longer than 1 character.

FILE *f = fopen("data.dat","rb");

You seem to be reading text ("r") file, not binary ("rb").

&jobs[i].name should be jobs[i].name

Upvotes: 2

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