MirOS Manual: fstat(2), lstat(2), stat(2)

STAT(2)                    BSD Programmer's Manual                     STAT(2)

NAME

     stat, lstat, fstat - get file status

SYNOPSIS

     #include <sys/types.h>
     #include <sys/stat.h>

     int
     stat(const char *path, struct stat *sb);

     int
     lstat(const char *path, struct stat *sb);

     int
     fstat(int fd, struct stat *sb);

DESCRIPTION

     The stat() function obtains information about the file pointed to by
     path. Read, write, or execute permission of the named file is not re-
     quired, but all directories listed in the path name leading to the file
     must be searchable.

     The lstat() function is identical to stat() except when the named file is
     a symbolic link, in which case lstat() returns information about the link
     itself, not the file the link references. Unlike other file system ob-
     jects, symbolic links do not have an owner, group, access mode, times,
     etc. Instead, these attributes are taken from the directory that contains
     the link. The only 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).

     The fstat() function obtains the same information about an open file
     known by the file descriptor fd.

     The sb argument is a pointer to a stat() structure as defined by
     <sys/stat.h> (shown below) and into which information is placed concern-
     ing the file.

     struct stat {
         dev_t      st_dev;    /* device inode resides on */
         ino_t      st_ino;    /* inode's number */
         mode_t     st_mode;   /* inode's mode */
         nlink_t    st_nlink;  /* number of hard links to the file */
         uid_t      st_uid;    /* user ID of owner */
         gid_t      st_gid;    /* group ID of owner */
         dev_t      st_rdev;   /* device type, for special file inode */
         struct timespec st_atimespec;  /* time of last access */
         struct timespec st_mtimespec;  /* time of last data modification */
         struct timespec st_ctimespec;  /* time of last file status change */
         off_t      st_size;   /* file size, in bytes */
         int64_t    st_blocks; /* blocks allocated for file */
         u_int32_t  st_blksize;/* optimal file sys I/O ops blocksize */
         u_int32_t  st_flags;  /* user defined flags for file */
         u_int32_t  st_gen;    /* file generation number */
     };

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

     st_atime     Time when file data was last accessed. Changed by the
                  mknod(2), utimes(2), and read(2) system calls.

     st_mtime     Time when file data was last modified. Changed by the
                  mknod(2), utimes(2), and write(2) system calls.

     st_ctime     Time when file status was last changed (inode data modifica-
                  tion). Changed by the chmod(2), chown(2), link(2), mknod(2),
                  rename(2), unlink(2), utimes(2), and write(2) system calls.

     The size-related fields of the struct stat are as follows:

     st_blksize     The optimal I/O block size for the file.

     st_blocks      The actual number of blocks allocated for the file in
                    512-byte units. As short symbolic links are stored in the
                    inode, this number may be zero.

     The status information word st_mode has the following bits:

     #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_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 */
     #define S_IRUSR  0000400  /* read permission, owner */
     #define S_IWUSR  0000200  /* write permission, owner */
     #define S_IXUSR  0000100  /* execute/search permission, owner */

     For a list of access modes, see <sys/stat.h>, access(2), and chmod(2).

RETURN VALUES

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

ERRORS

     stat() and lstat() will fail if:

     [ENOTDIR]     A component of the path prefix is not a directory.

     [ENAMETOOLONG]
                   A component of a pathname exceeded NAME_MAX characters, or
                   an entire path name exceeded PATH_MAX characters.

     [ENOENT]      The named file does not exist.

     [EACCES]      Search permission is denied for a component of the path
                   prefix.

     [ELOOP]       Too many symbolic links were encountered in translating the
                   pathname.

     [EFAULT]      sb or name points to an invalid address.

     [EIO]         An I/O error occurred while reading from or writing to the
                   file system.

     fstat() will fail if:

     [EBADF]       fd is not a valid open file descriptor.

     [EFAULT]      sb points to an invalid address.

     [EIO]         An I/O error occurred while reading from or writing to the
                   file system.

SEE ALSO

     chmod(2), chown(2), utimes(2), symlink(7)

STANDARDS

     Previous versions of the system used different types for the st_dev,
     st_uid, st_gid, st_rdev, st_size, st_blksize, and st_blocks fields.

     The stat() and fstat() function calls are expected to conform to IEEE Std
     1003.1-1988 ("POSIX").

HISTORY

     A stat() function appeared in Version 2 AT&T UNIX. An lstat() function
     call appeared in 4.2BSD.

CAVEATS

     The file generation number, st_gen, is only available to the superuser.

     The fields in the stat structure currently marked st_spare1, st_spare2,
     and st_spare3 are present in preparation for inode time stamps expanding
     to 64 bits. This, however, can break certain programs that depend on the
     time stamps being contiguous (in calls to utimes(2)).

BUGS

     Applying fstat() to a socket (and thus to a pipe) returns a zeroed
     buffer, except for the blocksize field, and a unique device and inode
     number.

MirOS BSD #10-current           April 19, 1994                               2

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