- c - 在位数组中找到第一个零
- linux - Unix 显示有关匹配两种模式之一的文件的信息
- 正则表达式替换多个文件
- linux - 隐藏来自 xtrace 的命令
在 fusexmp.c 中 http://www.gtoal.com/fusestuff/fuse-2.7.0/example/fusexmp.c.html
有一行<<12
st.st_mode = de->d_type << 12;
请指点一下为什么左移12位
d_type 文件的类型,即:DT_UNKNOWN我没有在 /usr/include/bits/dirent.h
谢谢
最佳答案
移位从目录条目d_type
转换而来位域到使用的值 int struct stat.st_mode
:
# define IFTODT(mode) (((mode) & 0170000) >> 12)
# define DTTOIF(dirtype) ((dirtype) << 12)
文档可以简单地在 man stat
中找到,因为值被分配给 st_mode
的 stat
结构:
The following flags are defined for the st_mode field:
S_IFMT 0170000 bit mask for the file type bit fields
S_IFSOCK 0140000 socket
S_IFLNK 0120000 symbolic link
S_IFREG 0100000 regular file
S_IFBLK 0060000 block device
S_IFDIR 0040000 directory
S_IFCHR 0020000 character device
S_IFIFO 0010000 FIFO
S_ISUID 0004000 set UID bit
S_ISGID 0002000 set-group-ID bit (see below)
S_ISVTX 0001000 sticky bit (see below)
S_IRWXU 00700 mask for file owner permissions
S_IRUSR 00400 owner has read permission
S_IWUSR 00200 owner has write permission
S_IXUSR 00100 owner has execute permission
S_IRWXG 00070 mask for group permissions
S_IRGRP 00040 group has read permission
S_IWGRP 00020 group has write permission
S_IXGRP 00010 group has execute permission
S_IRWXO 00007 mask for permissions for others (not in group)
S_IROTH 00004 others have read permission
S_IWOTH 00002 others have write permission
S_IXOTH 00001 others have execute permission
显然,de->d_type
相当于st_mode
的高位当左移 12 位时(信息,1<<12 == 0x1000
)。 man readdir
救援:
现在完整的转换和位掩码在 sys/dirent.h 中:
/* File types for `d_type'. */
enum
{
DT_UNKNOWN = 0, // The file type is unknown
DT_FIFO = 1, // This is a named pipe (FIFO).
DT_CHR = 2, // This is a character device.
DT_DIR = 4, // This is directory.
DT_BLK = 6, // This is a block device.
DT_REG = 8, // This is a regular file.
DT_LNK = 10, // This is a symbolic link.
DT_SOCK = 12, // This is a Unix domain socket.
DT_WHT = 14 // DT_CHR | DT_DIR | DT_REG
};
/* Convert between stat structure types and directory types. */
# define IFTODT(mode) (((mode) & 0170000) >> 12)
# define DTTOIF(dirtype) ((dirtype) << 12)
#endif
关于linux - 为什么在 fusexmp 中为 d_type 移动 12 位,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/8420234/
如果读取的文件类型是目录,我正在尝试做一个简单的比较,以便能够做一些事情。 示例代码: int main() { DIR *dir = opendir("."); struct dirent
我正在制作一个在 Linux shell 中运行的程序,它接受一个参数(一个目录),并显示目录中的所有文件及其类型。 输出应该是这样的: #include #include int main(
在 fusexmp.c 中 http://www.gtoal.com/fusestuff/fuse-2.7.0/example/fusexmp.c.html 有一行d_type > 12) # def
我有以下模仿 ls 的代码: #include #include char* dirent_type_to_str(unsigned char dirent_type) { switch (d
我是一名优秀的程序员,十分优秀!