stat() -- 获取文件大小

#include
#include     //exit()
#include     //strerror()
#include      //errno
#include //stat()
#include

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

    if (argc != 2) {
        printf("Please input filename\n");
        exit(-1);
    }
    filename = argv[1];
    if (stat(filename, &buf) < 0) {
        printf("Mesg: %s\n", strerror(errno));
        exit(-1);
    }
    printf("%s's size      is %-4d bytes\n", filename, buf.st_size);
    printf("%s's t_blksize is %-4d bytes\n", filename, buf.st_blksize);
    printf("%s's blocks    is %-4d blocks\n", filename, buf.st_blocks);
}

----------------------------------------------------
$ gcc test.c
$ ./a.out zengxiaolong
zengxiaolong's size      is 13   bytes
zengxiaolong's t_blksize is 4096 bytes
zengxiaolong's blocks    is 8    blocks
注: 文件zengxiaolong的实际内容为13个字节，占用4KB大小的磁盘空间(1 blocks -- 一块为4KB)




stat, fstat, lstat - get file status
----------------------------------------------------
    #include
    #include
    #include

    int stat (const char *path, struct stat *buf);
    int fstat(int      filedes, struct stat *buf);
    int lstat(const char *path, struct stat *buf);

    lstat函数与stat类似，但是当文件是一个符号连接时，lstat返回该符号连接的有关信息，而不是由该符号连接引用的文件的信息。


struct--stat
----------------------------------------------------
struct stat {
    mode_t    st_mode;    // file type & mode(permissions)
    ino_t     st_ino;     // i-node number(serial number)
    dev_t     st_dev;     // device number(filesystem)
    dev_t     st_rdev;    // device number for specials files
    nlink_t   st_nlink;   // number of links
    uid_t     st_uid;     // user ID of owner
    gid_t     st_gid;     // group ID of owner
    off_t     st_size;    // size in bytes, for regular files
    time_t    st_atime;   // time of last access
    time_t    st_mtime;   // time of last modification
    time_t    st_ctime;   // time of last file status change
    long      st_blksize; // best I/O block size
    long      st_blocks; -// number of 512-byte blocks allocated
};



struct--inode
----------------------------------------------------
/usr/src/linux/include/linux/fs.h
struct inode {
    struct hlist_node    -----------i_hash;
    struct list_head    ------------i_list;
    struct list_head    ------------i_sb_list;
    struct list_head      ----------i_dentry;
    unsigned long         ----------i_ino;
    atomic_t              ----------i_count;
    umode_t           --------------i_mode;
    unsigned int                    i_nlink;
    uid_t             --------------i_uid;
    gid_t             --------------i_gid;
    dev_t            ------------ --i_rdev;
    loff_t           -------------- i_size;
    struct timespec                 i_atime;
    struct timespec       ----------i_mtime;
    struct timespec       ----------i_ctime;
    unsigned int          ----------i_blkbits;
    unsigned long       ------------i_version;
    blkcnt_t          --------------i_blocks;
    unsigned short    --------------i_bytes;
    spinlock_t            ----------i_lock;
    struct mutex                    i_mutex;
    struct rw_semaphore             i_alloc_sem;
    struct inode_operations         *i_op;
    const struct file_operations    *i_fop;
    struct super_block              *i_sb;
    struct file_lock                *i_flock;
    struct address_space            *i_mapping;
    struct address_space            i_data;
#ifdef CONFIG_QUOTA
    struct dquot                    *i_dquot[MAXQUOTAS];
#endif
    struct list_head                i_devices;
    union {
        struct pipe_inode_info      *i_pipe;
        struct block_device         *i_bdev;
        struct cdev                 *i_cdev;
    };
    int                             i_cindex;   
    __u32                           i_generation;   
#ifdef CONFIG_DNOTIFY
    unsigned long                   i_dnotify_mask;
    struct dnotify_struct           *i_dnotify;
#endif
   
#ifdef CONFIG_INOTIFY
    struct list_head                inotify_watches;
    struct mutex                    inotify_mutex;
#endif
    unsigned long                   i_state;
    unsigned long                   dirtied_when;
    unsigned int                    i_flags;
    atomic_t                        i_writecount;
#ifdef CONFIG_SECURITY
    void                            *i_security;
#endif
    void                            *i_private;
#ifdef __NEED_I_SIZE_ORDERED
    seqcount_t                      i_size_seqcount;
#endif
};



struct--stat
----------------------------------------------------
/usr/src/linux/include/asm-i386/stat.h
struct stat {
    unsigned long --st_dev;
    unsigned long --st_ino;
    unsigned short -st_mode;
    unsigned short -st_nlink;
    unsigned short -st_uid;
    unsigned short -st_gid;
    unsigned long --st_rdev;
    unsigned long --st_size;
    unsigned long --st_blksize;
    unsigned long --st_blocks;
    unsigned long --st_atime;
    unsigned long --st_atime_nsec;
    unsigned long --st_mtime;
    unsigned long --st_mtime_nsec;
    unsigned long --st_ctime;
    unsigned long --st_ctime_nsec;
    unsigned long --__unused4;
    unsigned long --__unused5;
};