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.\"     @(#)stat.2	8.3 (Berkeley) 4/19/94
.\"
.Dd April 19, 1994
.Dt STAT 2
.Os BSD 4
.Sh NAME
.Nm fstat ,
.Nm fstat64 ,
.Nm lstat ,
.Nm lstat64 ,
.Nm stat ,
.Nm stat64
.Nd get file status
.Sh SYNOPSIS
.Fd #include <sys/stat.h>
.Ft int
.Fo fstat
.Fa "int fildes"
.Fa "struct stat *buf"
.Fc
.Ft int
.Fo fstat64
.Fa "int fildes"
.Fa "struct stat64 *buf"
.Fc
.Ft int
.Fo lstat
.Fa "const char *restrict path"
.Fa "struct stat *restrict buf"
.Fc
.Ft int
.Fo lstat64
.Fa "const char *restrict path"
.Fa "struct stat64 *restrict buf"
.Fc
.Ft int
.Fo stat
.Fa "const char *restrict path"
.Fa "struct stat *restrict buf"
.Fc
.Ft int
.Fo stat64
.Fa "const char *restrict path"
.Fa "struct stat64 *restrict buf"
.Fc
.Sh DESCRIPTION
The
.Fn stat
family of functions and their 64 bit variants obtain information about a file. The 
.Fn stat 
function obtains information about the file pointed to by
.Fa path .
Read, write or execute
permission of the named file is not required, but all directories
listed in the path name leading to the file must be searchable.
.Pp
.Fn Lstat
is like
.Fn stat
except in the case where the named file is a symbolic link,
in which case
.Fn lstat
returns information about the link,
while
.Fn stat
returns information about the file the link references.
Unlike other filesystem objects,
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
.Fn lstat
that refer to the symbolic link itself are the file type (S_IFLNK),
size, blocks, and link count (always 1).
.Pp
The
.Fn fstat
obtains the same information about an open file
known by the file descriptor
.Fa fildes .
.Pp
The
.Fa buf
argument is a pointer to a
.Fa stat
or
.Fa stat64
structure 
as defined by
.Aq Pa sys/stat.h
(both shown below)
and into which information is placed concerning the file.
.Bd -literal
struct stat {
    dev_t    st_dev;    /* device inode resides on */
    ino_t    st_ino;    /* inode's number */
    mode_t   st_mode;   /* inode protection mode */
    nlink_t  st_nlink;  /* number or 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 */
    quad_t   st_blocks; /* blocks allocated for file */
    u_long   st_blksize;/* optimal file sys I/O ops blocksize */
    u_long   st_flags;  /* user defined flags for file */
    u_long   st_gen;    /* file generation number */
};


struct stat64 {
    dev_t           st_dev;           /* ID of device containing file */
    mode_t          st_mode;          /* Mode of file (see below) */
    nlink_t         st_nlink;         /* Number of hard links */
    ino64_t 	    st_ino;          /* File serial number */
    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) */
    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 */
    uint32_t        st_gen;           /* file generation number */
    int32_t         st_lspare;        /* RESERVED: DO NOT USE! */
    int64_t         st_qspare[2];     /* RESERVED: DO NOT USE! */
};


.Ed
.Pp
The time-related fields of
.Fa struct stat
and
.Fa struct stat64
are as follows:
.Bl -tag -width XXXst_birthtime
.It st_atime
Time when file data last accessed.
Changed by the
.Xr mknod 2 ,
.Xr utimes 2
and
.Xr read 2
system calls.
.It st_mtime
Time when file data last modified.
Changed by the
.Xr mknod 2 ,
.Xr utimes 2
and
.Xr write 2
system calls.
.It st_ctime
Time when file status was last changed (inode data modification).
Changed by the
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr link 2 ,
.Xr mknod 2 ,
.Xr rename 2 ,
.Xr unlink 2 ,
.Xr utimes 2
and
.Xr write 2
system calls.
.It st_birthtime
Time of file creation. Only set once when the file is created. This field is 
only available in the 64 bit variants. On filesystems where birthtime is 
not available, this field holds the
.Fa ctime
instead.
.El
.Pp
The size-related fields of the structures are as follows:
.Bl -tag -width XXXst_blksize
.It st_blksize
The optimal I/O block size for the file.
.It 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.
.El
.Pp
The status information word
.Fa st_mode
has the following bits:
.Bd -literal
#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 */
#define S_IRUSR 0000400  /* read permission, owner */
#define S_IWUSR 0000200  /* write permission, owner */
#define S_IXUSR 0000100  /* execute/search permission, owner */
.Ed
.Pp
For a list of access modes, see
.Aq Pa sys/stat.h ,
.Xr access 2
and
.Xr chmod 2 .
.Pp
For a list of the file flags in the
.Fa st_flags
field, see
.Aq Pa sys/stat.h
and
.Xr chflags 2 .
.Sh RETURN VALUES
Upon successful completion a value of 0 is returned.
Otherwise, a value of -1 is returned and
.Va errno
is set to indicate the error.
.Sh COMPATIBILITY
Previous versions of the system used different types for the
.Li st_dev ,
.Li st_uid ,
.Li st_gid ,
.Li st_rdev ,
.Li st_size ,
.Li st_blksize
and
.Li st_blocks
fields.
.Sh ERRORS
.Bl -tag -width Er
The
.Fn fstat
system call will fail if:
.\" ===========
.It Bq Er EBADF
.Fa fildes
is not a valid open file descriptor.
.\" ===========
.It Bq Er EFAULT
.Fa Sb
points to an invalid address.
.\" ===========
.It Bq Er EIO
An I/O error occurs while reading from or writing to the file system.
.El
.Pp
The
.Fn lstat
and
.Fn stat
system calls will fail if:
.Bl -tag -width Er
.\" ===========
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.\" ===========
.It Bq Er EFAULT
.Fa Sb
or
.Em name
points to an invalid address.
.\" ===========
.It Bq Er EIO
An I/O error occurs while reading from or writing to the file system.
.\" ===========
.It Bq Er ELOOP
Too many symbolic links are encountered in translating the pathname.
This is taken to be indicative of a looping symbolic link.
.\" ===========
.It Bq Er ENAMETOOLONG
A component of a pathname exceeds
.Dv {NAME_MAX}
characters, or an entire path name exceeds
.Dv {PATH_MAX}
characters.
.\" ===========
.It Bq Er ENOENT
The named file does not exist.
.\" ===========
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.El
.Pp
The
.Fn fstat ,
.Fn lstat ,
and
.Fn stat
system calls will fail if:
.Bl -tag -width Er
.\" ===========
.It Bq Er EOVERFLOW
The file size in bytes 
or the number of blocks allocated to the file
or the file serial number cannot be represented correctly
in the structure pointed to by
.Fa buf .
.El
.Sh CAVEATS
The file generation number,
.Fa st_gen ,
is only available to the super-user.
.br
The fields in the stat structure currently marked
.Fa st_spare1 ,
.Fa st_spare2 ,
and
.Fa 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
.Xr utimes 2 ) .
.Sh LEGACY SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/stat.h>
.Pp
The include file
.In sys/types.h
is necessary.
.Sh SEE ALSO
.Xr chflags 2 ,
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr utimes 2 ,
.Xr compat 5 ,
.Xr symlink 7
.Sh BUGS
Applying
.Xr 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.
.Sh STANDARDS
The
.Fn stat
and
.Fn fstat
function calls are expected to conform to 
.St -p1003.1-88 .
.Sh HISTORY
An
.Fn lstat
function call appeared in
.Bx 4.2 .
The 
.Fn stat64 ,
.Fn fstat64 ,
and
.Fn lstat64
system calls first appeared in Mac OS X 10.5 (Leopard).