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Ò».dd
dd if=/dev/zero of=1T.img bs=1G seek=1024 count=0
bs=1G±íʾÿһ´Î¶Áд1GÊý¾Ý£¬count=0±íʾ¶Áд0´Î£¬seek=1024±íʾÂÔ¹ý1024¸öBlock²»Ð´£¬Ç°Ãæblock sizeÊÇ1G£¬ËùÒÔ¹²ÂÔ¹ý1T£¡
ÕâÊÇ´´½¨´óÐÍsparseÎļþ×î¼òµ¥µÄ·½·¨¡£
 
¶þ.ftruncate64/ftruncate
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Îļþsparse.c:
 
//OPTION 1:ÊÇ·ñ¶¨ÒåÓë´óÎļþÏà¹ØµÄºê
#define _LARGEFILE_SOURCE
#define _LARGEFILE64_SOURCE
#define _FILE_OFFSET_BITS 64
 
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#define FILENAME "bigfile"
#define FILE_MODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
int main(int argc, char **argv)
{
  int fd, ret;
  off_t offset;
  int total = 0;
  if ( argc >= 2 )
  {
  total = atol(argv[1]);
  printf("total=%d\n", total);
  }
 
  //OPTION 2:ÊÇ·ñÓÐO_LARGEFILEÑ¡Ïî
  //fd = open(FILENAME, O_RDWR|O_CREAT|O_LARGEFILE, 0644);
  fd = open(FILENAME, O_RDWR|O_CREAT, 0644);
  if (fd < 0) {
  perror(FILENAME);
  return -1;
  }
  offset = (off_t)total *1024ll*1024ll*1024ll;
  printf("offset=%ld\n", offset);
 
  //OPTION 3£ºÊÇ·ñµ÷ÓÃ64λϵͳº¯Êý
  //if (ftruncate64(fd, offset) < 0)
  if (ftruncate(fd, offset) < 0)
  {
  printf("[%d]-ftruncate64 error: %s\n", errno, strerror(errno));
  close(fd);
  return 0;
  }
  close(fd);
  printf("OK\n");
  return 0;
}
 
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linux:/disk/test/big # gcc --version
gcc (GCC) 3.3.5 20050117 (prerelease) (SUSE Linux)
linux:/disk/test/big # uname -a
Linux linux 2.6.11.4-20a-default #1 Wed Mar 23 21:52:37 UTC 2005 i686 i686 i386 GNU/Linux
 
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