libc/sys/stat.2

.\" Copyright (c) 1980, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)stat.2	8.1 (Berkeley) 06/04/93
.\"
.Dd
.Dt STAT 2
.Os BSD 4
.Sh NAME
.Nm stat ,
.Nm lstat ,
.Nm fstat
.Nd get file status
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/stat.h>
.Ft int
.Fn stat "const char *path" "struct stat *buf"
.Ft int
.Fn lstat "const char *path" "struct stat *buf"
.Ft int
.Fn fstat "int fd" "struct stat *buf"
.Sh DESCRIPTION
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 seachable.
.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 fd ,
such as would
be obtained by an
.Xr open
call.
.Pp
.Fa Buf
is a pointer to a
.Fn stat
structure
as defined by
.Aq Pa sys/stat.h
(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 */
    off_t    st_size;   /* file size, in bytes */
    time_t   st_atime;  /* time of last access */
    long     st_spare1;
    time_t   st_mtime;  /* time of last data modification */
    long     st_spare2;
    time_t   st_ctime;  /* time of last file status change */
    long     st_spare3;
    long     st_blksize;/* optimal file sys I/O ops blocksize */
    long     st_blocks; /* blocks allocated for file */
    u_long   st_flags;  /* user defined flags for file */
    u_long   st_gen;    /* file generation number */
};
.Ed
.Pp
The time-related fields of
.Fa struct stat
are as follows:
.Bl -tag -width st_blocks
.It st_atime
Time when file data last accessed.  Changed by the following system
calls:
.Xr mknod 2 ,
.Xr utimes 2 ,
and
.Xr read 2 .
.It st_mtime
Time when file data last modified.
Changed by the following system calls:
.Xr mknod 2 ,
.Xr utimes 2 ,
.Xr write 2 .
.It st_ctime
Time when file status was last changed (inode data modification).
Changed by the following system calls:
.Xr chmod 2
.Xr chown 2 ,
.Xr link 2 ,
.Xr mknod 2 ,
.Xr rename 2 ,
.Xr unlink 2 ,
.Xr utimes 2 ,
.Xr write 2 .
.It st_blocks
The actual number of blocks allocated for the file in 512-byte units.
.El
.Pp
The status information word
.Fa st_mode
has 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_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 .
.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 ERRORS
.Fn Stat
and
.Fn lstat
will fail if:
.Bl -tag -width ENAMETOOLONGAA
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er EINVAL
The pathname contains a character with the high-order bit set.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 255 characters,
or an entire path name exceeded 1023 characters.
.It Bq Er ENOENT
The named file does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EFAULT
.Fa Buf
or
.Em name
points to an invalid address.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Pp
.Bl -tag -width [EFAULT]
.Fn Fstat
will fail if:
.It Bq Er EBADF
.Fa fd
is not a valid open file descriptor.
.It Bq Er EFAULT
.Fa Buf
points to an invalid address.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Sh CAVEAT
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 SEE ALSO
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr utimes 2
.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 IEEE Std 1003.1-1988
.Pq Dq Tn POSIX .
.Sh HISTORY
A
.Nm lstat
function call appeared in
.Bx 4.2 .