CODEWITHSUNDEEP
cfile-io
Milk
Milk

Reputation: 657

while(!feof(file)) reading extra line

Im having an issue reading in lines from a file. Basically my code is reading in one extra line than it should with all variables being '0'i.e.

If my file is:

0, 0, 3, 64, 0, 0, 0, 0
2, 0, 6, 64, 0, 0, 0, 0
4, 0, 4, 64, 0, 0, 0, 0
6, 0, 5, 64, 0, 0, 0, 0
8, 0, 2, 64, 0, 0, 0, 0

it will read in:

Object 1:  0, 0, 3, 64, 0, 0, 0, 0
Object 2:  2, 0, 6, 64, 0, 0, 0, 0
Object 3:  4, 0, 4, 64, 0, 0, 0, 0
Object 4:  6, 0, 5, 64, 0, 0, 0, 0
Object 5:  8, 0, 2, 64, 0, 0, 0, 0
Object 6:  0, 0, 0,  0, 0, 0, 0, 0

Here is my read algorithm:

while (!feof(pfile)) { 

        PcbPtr p = createnullPcb();
        fscanf(pfile, "%d,%d,%d,%d,%d,%d,%d,%d", &p->arrivaltime, &p->priority, &p->remainingcputime, 
        &p->memalloc, &p->pr,  &p->sc, &p->mo, &p->cd);
        char cwd[1024];
        char *tmp = getcwd(cwd, sizeof(cwd));
        strcat(tmp, "/process");
        p->args[0] = tmp;
        p->args[1] = NULL;

        if (!headi) {
            headi = p;
        } 
        else {
            enqPcb(&headi, p);
        }

    }

Why is this happening? Thanks for any help!

Upvotes: 3

Views: 1796

Answers (1)

K-ballo
K-ballo

Reputation: 81349

What's happening is that feof returns true when there was an attempt to read past the end. When you are at the end of your file, but haven't tried to read anything else yet, feof will return false.

In simple words: feof does not stand for is at the end of the file, but for has attempted to access past the end of the file.

Note that when you are at the end of the file and try to read that extra line, fscanf will fail. You could check its return value to see if it was able to read anything.

Upvotes: 4

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