stat 的 st_blksize 是以位还是字节为单位测量的？

Question

我正在尝试使用这些行查找我机器上的块大小：

struct stat fi;
stat("/tmp", &fi);
BLOCK_SIZE = fi.st_blksize;

BLOCK_SIZE是代表bytes的数量还是bits单个块的数量？

文档说：

" blksize_t st_blksize; /* blocksize for file system I/O */ "

Answer 1

块大小通常以字节为单位给出，在 stat 的情况下就是这样。按位给出它没有多大意义。

Answer 2

如果你阅读 this POSIX <sys/stat.h> reference 你会发现

The unit for the st_blocks member of the stat structure is not defined within POSIX.1-2008. In some implementations it is 512 bytes. It may differ on a file system basis. There is no correlation between values of the st_blocks and st_blksize, and the f_bsize (from <sys/statvfs.h> structure members.

因此，虽然 st_blksize 没有标准化单位，但它不太可能以位为单位。要获得实际单位，您必须研究当前的操作系统，甚至可能使用的文件系统。

Linux stat manual page doesn't mention the unit explicitly, but in the example它说的单位是字节。

Answer 3

它在Bytes。请参阅 Linux 手册页示例代码 here:-

printf("Preferred I/O block size: %ld bytes\n", (long) sb.st_blksize);

  The following program calls stat() and displays selected fields in
   the returned stat structure.

   #include <sys/types.h>
   #include <sys/stat.h>
   #include <time.h>
   #include <stdio.h>
   #include <stdlib.h>
   #include <sys/sysmacros.h>

   int
   main(int argc, char *argv[])
   {
       struct stat sb;

       if (argc != 2) {
           fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
           exit(EXIT_FAILURE);
       }

       if (stat(argv[1], &sb) == -1) {
           perror("stat");
           exit(EXIT_FAILURE);
       }

       printf("ID of containing device:  [%lx,%lx]\n",
            (long) major(sb.st_dev), (long) minor(sb.st_dev));

       printf("File type: ");

       switch (sb.st_mode & S_IFMT) {
       case S_IFBLK:  printf("block device\n");            break;
       case S_IFCHR:  printf("character device\n");        break;
       case S_IFDIR:  printf("directory\n");               break;
       case S_IFIFO:  printf("FIFO/pipe\n");               break;
       case S_IFLNK:  printf("symlink\n");                 break;
       case S_IFREG:  printf("regular file\n");            break;
       case S_IFSOCK: printf("socket\n");                  break;
       default:       printf("unknown?\n");                break;
       }

       printf("I-node number:            %ld\n", (long) sb.st_ino);

       printf("Mode:                     %lo (octal)\n",
               (unsigned long) sb.st_mode);

       printf("Link count:               %ld\n", (long) sb.st_nlink);
       printf("Ownership:                UID=%ld   GID=%ld\n",
               (long) sb.st_uid, (long) sb.st_gid);

       printf("Preferred I/O block size: %ld bytes\n",
               (long) sb.st_blksize);
       printf("File size:                %lld bytes\n",
               (long long) sb.st_size);
       printf("Blocks allocated:         %lld\n",
               (long long) sb.st_blocks);

       printf("Last status change:       %s", ctime(&sb.st_ctime));
       printf("Last file access:         %s", ctime(&sb.st_atime));
       printf("Last file modification:   %s", ctime(&sb.st_mtime));

       exit(EXIT_SUCCESS);
   }

stat 的 st_blksize 是以位还是字节为单位测量的？

Is stat's st_blksize measured in bits or bytes?

c

posix

stat