File system stats

Question

I use the following code to find the disk usage of my /

int main()
{
    struct statfs *stat;
    statfs64("/tmp",stat);
    perror("");
    printf("%lu \n",stat->f_bfree*stat->f_bsize);
    return 0;
}

The perror keeps on printing "Bad Address" and a random number for size.

Bad address

3264987920

PS:I tried sudo ./a.out,statfs("a.out",stat)

What may be the issue?

score 4 · Accepted Answer · answered Apr 17 '13 at 01:44

4

You've declared a pointer to a statfs struct but don't actually have space allocated for such a struct. The pointer points off into nowhereland. It's uninitialized, it doesn't point anywhere legal.

struct statfs stat;

if (statfs64("/tmp", &stat) == -1) {
    perror("statfs64");
}
else {
    printf("%lu\n", stat.f_bfree * stat.f_bsize);
}

answered Apr 17 '13 at 01:44

John Kugelman

349,597
67
533
578

Thanks:) that worked :)I would like to add that `statfs64` may trigger a segmentation fault,which can be removed by using `statfs` instead – rjv Apr 17 '13 at 01:52
@RajeevS Right. `statfs()` and `struct statfs` should be used together, and `statfs64()` and `struct statfs64` as well. The use of the latter is deprecated; they are used instead of `statfs()` if the correct symbols are defined. – glglgl Apr 17 '13 at 10:03

score 0 · Answer 2 · answered Apr 17 '13 at 09:15

0

You have used statfs *stat with no memory allocation hence wild pointer usage it may point to anywhere ( illegal memory address) Either Initialise it with valid memory or use variable and pass its reference.

answered Apr 17 '13 at 09:15

anshul garg

473
3
7

You are saying the same as [John said 7 1/2 hours before you...](http://stackoverflow.com/a/16050052/296974) – glglgl Apr 17 '13 at 10:03

File system stats

2 Answers2