STAT(2) BSD System Calls Manual STAT(2)

     fstat, fstat64, lstat, lstat64, stat, stat64 -- get file status

     int fstat(int fildes, struct stat *buf); 
     int lstat(const char *restrict path, struct stat *restrict buf); 
     int  stat(const char *restrict path, struct stat *restrict buf); 
transitiional synopsis (now deprecated) Not shown here.
     int fstat64(int fildes, struct stat64 *buf); 
     int lstat64(const char *restrict path, struct stat64 *restrict buf); int
     stat64(const char *restrict path, struct stat64 *restrict buf);
The stat() function obtains information about the file pointed to by path. Permission to file is not required, directories in the path leading to the file must be searchable (x mode).

Symbolic links do not have an owner, group, access mode, times, etc., these attributes may be taken from the directory that contains the link. the attributes returned from an lstat() that refer to the symbolic link itself are the file type (S_IFLNK), size, blocks, and link count (always 1). stat() returns information about the file the link references. lstat() returns information about the link where the named file is a symbolic link;

fstat() obtains information about an open file fields

buf is a pointer to a stat structure as defined by <sys/stat.h> where information is placed.

     struct stat {
         dev_t           st_dev;           /* ID of device containing file */
         mode_t          st_mode;          /* Mode of file */
         nlink_t         st_nlink;         /* Number of hard links */
         ino_t           st_ino;           /* File serial number                64 bits */
         uid_t           st_uid;           /* User ID of the file */
         gid_t           st_gid;           /* Group ID of the file */
         dev_t           st_rdev;          /* Device ID */
         struct timespec st_atimespec;     /* time of last access */
         struct timespec st_mtimespec;     /* time of last data modification */
         struct timespec st_ctimespec;     /* time of last status change */
         struct timespec st_birthtimespec; /* time of file creation(birth)         added   */
         off_t           st_size;          /* file size, in bytes */
         blkcnt_t        st_blocks;        /* blocks allocated for file */
         blksize_t       st_blksize;       /* optimal blocksize for I/O */
         uint32_t        st_flags;         /* user defined flags for file */  //UF_COMPRESSED 
         uint32_t        st_gen;           /* file generation number */

     The time-related fields of struct stat are as follows:

     st_atime         data last accessed.  Changed by the mknod, utimes and read (if file system has atime on)
     st_mtime         file data last modified.  Changed by the mknod, utimes and write
     st_ctime         status was last changed (inode data modification).  chmod, chown, link, mknod, rename, unlink, utimes and write
     st_birthtime     file creation.  
     st_blksize     optimal I/O block size for the file.  
     st_blocks      number of blocks allocated for the file in 512-byte units. May be zero for symblolic links.

     st_mode : 
     #define S_IFMT   0170000 /* type of file */
     #define S_IFIFO  0010000  /* named pipe (fifo) */
     #define S_IFCHR  0020000  /* character special */
     #define S_IFDIR  0040000  /* directory */
     #define S_IFBLK  0060000  /* block special */
     #define S_IFREG  0100000  /* regular */
     #define S_IFLNK  0120000  /* symbolic link */
     #define S_IFSOCK 0140000  /* socket */
     #define S_IFWHT  0160000  /* whiteout */

     #define S_ISUID  0004000  /* set user id on execution */
     #define S_ISGID  0002000  /* set group id on execution */
     #define S_ISVTX  0001000  /* save swapped text even after use (sticky) */
     #define S_IRUSR  0000400  /* read permission, user(owner) */
     #define S_IWUSR  0000200  /* write permission, user(owner) */
     #define S_IXUSR  0000100  /* execute/search permission, user(owner) */

     For a list of access modes, see <sys/stat.h> access and chmod.  
     For a list of the file flags in the st_flags field, see <sys/stat.h> and chflags.


Upon successful completion a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.


    fstat() system call will fail if: 
     [EBADF]            fildes is not a valid open file descriptor.  
     [EFAULT]           Sb points to an invalid address.  
     [EIO]              An I/O error occurs while reading from or writing to the file system.  

    lstat() and stat() system calls will fail if: 
     [EACCES]           Search permission is denied for a component of the path prefix.  
     [EFAULT]           Sb or name points to an invalid address.  
     [EIO]              An I/O error occurs while reading from or writing to the file system.  
     [ELOOP]            Too many symbolic links are encountered in translating the pathname,  indicative of a looping symbolic link.  
     [ENAMETOOLONG]     A component of a pathname exceeds {NAME_MAX} characters, or an entire path name exceeds {PATH_MAX} characters.  
     [ENOENT]           The named file does not exist.  
     [ENOTDIR]          A component of the path prefix is not a directory.

    fstat(), lstat(), and stat() system calls will fail if: 
     [EOVERFLOW]        The file size in bytes, the number of blocks allocated to the file or the file serial number cannot
                        be represented correctly in the structure pointed to by buf.


Generation number, st_gen, is only available to the super-user. The stat64 structure used by these deprecated routines is the same as the stat structure when 64-bit inodes are in effect SEE ALSO chflags(2), chmod(2), chown(2), utimes(2), compat(5), statfs(2), symlink(7) BUGS Applying fstat to a socket (and thus to a pipe) returns a zero'd buffer, except for the blocksize field, and a unique device and inode number.