Re: How to lseek the larger file > 2GB under linux

Hi Michal,

The "LL" does make my prog work :)

Thanks for your help!!

Best Regard
Nicle Yang


>
>
> 2009/5/18 Michal Nazarewicz <[email protected]>
>>
>> Nicle <[email protected]> writes:
>> > I have a file > 2GB, and my job is seeking the file to pos: 2.1G.
>> > But, it seems that the lseek64 doesn't work.
>>
>> > #define _LARGEFILE64_SOURCE
>> > #include ...
>> >
>> > int main() {
>> >  int fd = -1;
>> >  long long pos = (long long) 2*1024*1024*1024 + 10; // over 2G
>>
>> A long shot, but try (2LL << 30) (the "LL" is important).  I don't
>> expect that will make it work but if you're out of ideas... ;)
>>
>> >  fd = open(FILENAME, O_WRONLY|O_LARGEFILE);
>> >  if (fd < 0) { /* ... */ }
>> >
>> >  if (lseek64(fd, pos, SEEK_SET) < 0)
>> >      fprintf(stderr, "Failed seeking to %lld, %s\n", pos, strerror(errno));
>> >
>> >  return 0;
>> > }
>>
>> >  Then the building cmd:   gcc -o test test.c -D_FILE_OFFSET_BITS=64
>> >  Output:            >     Failed seeking to 2147483658, Success.
>> >
>> > The return val of lseek64  was "<0", but the strerror told me "Success".
>>
>> BTW. The following works fine for me:
>>
>> #v+
>> #define _LARGEFILE64_SOURCE
>>
>> #include <errno.h>
>> #include <fcntl.h>
>> #include <stdio.h>
>> #include <string.h>
>> #include <sys/stat.h>
>> #include <sys/types.h>
>> #include <unistd.h>
>>
>> #define RUN(expr) if ((expr) < 0) { perror(#expr); return 1; } else (void)0
>>
>> int main(void) {
>>        const long long pos = (2LL << 30) + 10;
>>        int fd;
>>
>>        RUN(fd = open("deleteme", O_WRONLY | O_LARGEFILE | O_CREAT, 0600));
>>        RUN(lseek64(fd, pos, SEEK_SET));
>>        RUN(write(fd, "a", 1));
>>        return 0;
>> }
>> #v-
>>
>> --
>> Best regards,                                         _     _
>>  .o. | Liege of Serenly Enlightened Majesty of      o' \,=./ `o
>>  ..o | Computer Science,  Michal "mina86" Nazarewicz   (o o)
>>  ooo +--<mina86*tlen.pl>--<jid:mina86*jabber.org>--ooO--(_)--Ooo--
>
--
To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html