Nicle wrote:
> Hi all,
>
> 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.
> Here is the sample code:
>
> #define _LARGEFILE64_SOURCE
> #include ...
>
> int main()
> {
> int fd = -1;
> long long pos = (long long) 2*1024*1024*1024 + 10; // over 2G
>
> 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".
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>
>
I changed the below a little, but when I seeked to 2.1GB,
it worked fine. I am not writing like you, but reading.
#define _LARGEFILE64_SOURCE
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
int main()
{
int fd, ret;
size_t count = 200;
long long pos = (long long) 2*1024*1024*1024 + 10; // over 2G
char buf[count];
fd = open("/tmp/fish", O_RDONLY|O_LARGEFILE);
if (fd < 0){
fprintf(stderr, "%s\n", strerror(errno));
exit(1);
}
if (lseek64(fd, pos, SEEK_SET) < 0) {
fprintf(stderr, "Failed seeking to %lld, %s\n", pos, strerror(errno));
exit(1);
}
if ((ret = read(fd, buf, count)) < 0) {
fprintf(stderr, "Failed reading: %s\n", strerror(errno));
exit(1);
}
buf[ret] = 0x00;
printf("%s\n", buf);
close(fd);
return 0;
}
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