path: root/lib/libc/sys/stat.2

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.\"     @(#)stat.2	8.4 (Berkeley) 5/1/95
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.Dd February 15, 2002
.Dt STAT 2
.Os
.Sh NAME
.Nm stat ,
.Nm lstat ,
.Nm fstat
.Nd get file status
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/types.h
.In sys/stat.h
.Ft int
.Fn stat "const char *path" "struct stat *sb"
.Ft int
.Fn lstat "const char *path" "struct stat *sb"
.Ft int
.Fn fstat "int fd" "struct stat *sb"
.Sh DESCRIPTION
The
.Fn stat
system call 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
The
.Fn lstat
system call 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.
.Pp
The
.Fn fstat
system call obtains the same information about an open file
known by the file descriptor
.Fa fd .
.Pp
The
.Fa sb
argument is a pointer to a
.Vt 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;               /* inode's device */
    ino_t     st_ino;               /* inode's number */
    mode_t    st_mode;              /* inode protection mode */
    nlink_t   st_nlink;             /* number of hard links */
    uid_t     st_uid;               /* user ID of the file's owner */
    gid_t     st_gid;               /* group ID of the file's group */
    dev_t     st_rdev;              /* device type */
#ifndef _POSIX_SOURCE
    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 */
#else
    time_t    st_atime;             /* time of last access */
    long      st_atimensec;         /* nsec of last access */
    time_t    st_mtime;             /* time of last data modification */
    long      st_mtimensec;         /* nsec of last data modification */
    time_t    st_ctime;             /* time of last file status change */
    long      st_ctimensec;         /* nsec of last file status change */
#endif
    off_t     st_size;              /* file size, in bytes */
    int64_t   st_blocks;            /* blocks allocated for file */
    u_int32_t st_blksize;           /* optimal blocksize for I/O */
    fflags_t  st_flags;             /* user defined flags for file */
    u_int32_t st_gen;               /* file generation number */
};
.Ed
.Pp
The time-related fields of
.Fa struct stat
are as follows:
.Bl -tag -width XXXst_mtime
.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.
.El
.Pp
If
.Dv _POSIX_SOURCE
is not defined, the time-related fields are defined as:
.Bd -literal
#ifndef _POSIX_SOURCE
#define st_atime st_atimespec.tv_sec
#define st_mtime st_mtimespec.tv_sec
#define st_ctime st_ctimespec.tv_sec
#endif
.Ed
.Pp
The size-related fields of the
.Vt "struct stat"
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 .
.Sh RETURN VALUES
.Rv -std
.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
The
.Fn stat
and
.Fn lstat
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
The
.Fa sb
or
.Fa path
argument
points to an invalid address.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.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 ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er EOVERFLOW
The file size in bytes cannot be
represented correctly in the structure pointed to by
.Fa sb .
.El
.Pp
.Bl -tag -width Er
The
.Fn fstat
system call will fail if:
.It Bq Er EBADF
The
.Fa fd
argument
is not a valid open file descriptor.
.It Bq Er EFAULT
The
.Fa sb
argument
points to an invalid address.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.It Bq Er EOVERFLOW
The file size in bytes cannot be
represented correctly in the structure pointed to by
.Fa sb .
.El
.Sh SEE ALSO
.Xr access 2 ,
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr utimes 2 ,
.Xr symlink 7
.Sh BUGS
Applying
.Fn 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.
.Sh STANDARDS
The
.Fn stat
and
.Fn fstat
system calls are expected to conform to
.St -p1003.1-90 .
.Sh HISTORY
The
.Fn stat
and
.Fn fstat
system calls appeared in
.At v7 .
The
.Fn lstat
system call appeared in
.Bx 4.2 .