C Language, Checking file sizes

Bert Ede
#1 / 5

Checking file sizes

Greetings...
I may have been looking at the source and K&R too long, but for some
reason, I can't find an easy way to retrieve the size of a file. I use
QuickC (IBM PC). Anything ANSI standard would be appreciated, but if it's
"tweakable", that would be great, too.

Thanks...
Bert

* Origin: Hillbilly Korner BBS - (501)751-3714 (1:391/1160)

Sat, 17 Sep 1994 03:18:00 GMT

Chris Webst
#2 / 5

Checking file sizes

fp = fopen(file, "r");
fseek(fp, 0L, 2);
size = ftell(fp);

or

struct stat buf;

stat(file, &buf);
size = buf.st_size;

--Chris

Sat, 17 Sep 1994 23:46:52 GMT

atmt..
#3 / 5

Checking file sizes

Quote:

> Greetings...
> I may have been looking at the source and K&R too long, but for some
> reason, I can't find an easy way to retrieve the size of a file. I use
> QuickC (IBM PC). Anything ANSI standard would be appreciated, but if it's
> "tweakable", that would be great, too.

> Thanks...
> Bert

> * Origin: Hillbilly Korner BBS - (501)751-3714 (1:391/1160)

I don't know how well this transports to Quick C: in Unix I have used

FILE *f;
long length;

f = fopen(....);
fseek(f, 0L, 2); /* position at 0 bytes (0L) from end of file (2) */
length = ftell(f); /* return where we are now */

and then re fseek() to go back to the beginning.
It doesn't seem to read the whole file in this process -
the file I'm checking is 66 MB long and it does it instantaneously.

Tim Kingsmill-Vellacott
Atmospheric, Oceanic and Planetary Physics
University of Oxford

Sun, 18 Sep 1994 00:26:57 GMT

David F. Sko
#4 / 5

Checking file sizes

Quote:

(Chris Webster) writes:
>fp = fopen(file, "r");
>fseek(fp, 0L, 2);
>size = ftell(fp);
>or
>struct stat buf;
>stat(file, &buf);
>size = buf.st_size;

Note that while both of these may very well work with QuickC, there is
no standard, portable way to determine the size of a file (other than
opening it and reading to EOF, I suppose. Even then, you have to
worry about MS-DOG's "ascii" and "binary" modes of reading. VMS
probably throws a few twists with the different file formats, too.)

Ftell is guaranteed only to return a "magic cookie" that will work with
fseek; it does not have to have any physical meaning. And stat is available
only on Unix systems and systems which emulate the Unix C library.

--
David F. Skoll

Sun, 18 Sep 1994 03:06:42 GMT

Kenneth Herr
#5 / 5

Checking file sizes

Quote:

>> I may have been looking at the source and K&R too long, but for some
>> reason, I can't find an easy way to retrieve the size of a file. I use
>> QuickC (IBM PC). Anything ANSI standard would be appreciated, but if it's
>> "tweakable", that would be great, too.
>[Uses this under unix}
>FILE *f;
>long length;
>f = fopen(....);
>fseek(f, 0L, 2); /* position at 0 bytes (0L) from end of file (2) */
>length = ftell(f); /* return where we are now */

Be aware this is not guaranteed to work. The return value of ftell and
the second argument to fseek are not required to byte-counts from any
particular point; it's allowed for these values to be magic cookies. The
only requirement is that fseek() will take the result of an ftell() and
return to that spot.
--

University of Kentucky +1 606 257 2975
Department of Mathematics
Flame early, flame often.

Sun, 18 Sep 1994 11:16:55 GMT