libc/sys/stat.2

.\" Copyright (c) 1980, 1991, 1993, 1994
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)stat.2	8.4 (Berkeley) 5/1/95
.\" $FreeBSD: src/lib/libc/sys/stat.2,v 1.16.2.7 2001/12/14 18:34:01 ru Exp $
.\"
.Dd September 13, 2019
.Dt STAT 2
.Os
.Sh NAME
.Nm stat ,
.Nm lstat ,
.Nm fstat ,
.Nm fstatat
.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"
.Ft int
.Fn fstatat "int fd" "const char *path" "struct stat *buf" "int flag"
.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
.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.
.Pp
The
.Fn fstat
system call obtains the same information about an open file
known by the file descriptor
.Fa fd .
.Pp
The
.Fn fstatat
system call is equivalent to
.Fn stat
and
.Fn lstat
except in the case where the
.Fa path
specifies a relative path.
In this case the status is retrieved from a file relative to
the directory associated with the file descriptor
.Fa fd
instead of the current working directory.
.Pp
The values for the
.Fa flag
are constructed by a bitwise-inclusive OR of flags from the following list,
defined in
.In fcntl.h :
.Bl -tag -width indent
.It Dv AT_SYMLINK_NOFOLLOW
If
.Fa path
names a symbolic link, the status of the symbolic link is returned.
.El
.Pp
If
.Fn fstatat
is passed the special value
.Dv AT_FDCWD
in the
.Fa fd
parameter, the current working directory is used and the behavior is
identical to a call to
.Fn stat
or
.Fn lstat
respectively, depending on whether or not the
.Dv AT_SYMLINK_NOFOLLOW
bit is set in
.Fa flag .
.Pp
The
.Fa sb
argument is a pointer to a
.Vt stat
structure
as defined by
.In sys/stat.h
(shown below)
and into which information is placed concerning the file.
.Bd -literal
struct stat {
    ino_t     st_ino;               /* inode's number */
    nlink_t   st_nlink;             /* number of hard links */
    dev_t     st_dev;               /* inode's device */
    mode_t    st_mode;              /* inode protection mode */
    uint16_t  st_padding1;
    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 */
    struct timespec st_atim;        /* time of last access */
    struct timespec st_mtim;        /* time of last data modification */
    struct timespec st_ctim;        /* time of last file status change */
    off_t     st_size;              /* file size, in bytes */
    blkcnt_t  st_blocks;            /* blocks allocated for file */
    u_int32_t __old_st_blksize;     /* (for old ABI compat only, do not use) */
    u_int32_t st_flags;             /* user defined flags for file */
    u_int32_t st_gen;               /* file generation number */
    int32_t   st_lspare;
    blksize_t st_blksize;	    /* optimal blocksize for I/O */
    int64_t   st_qspare2;           /* (placeholder for future, do not use) */
};
.Ed
.Pp
The time-related fields of
.Vt struct stat
are as follows:
.Bl -tag -width ".Fa st_mtime"
.It Fa st_atim
Time when file data last accessed.
Changed by the
.Xr execve 2 ,
.Xr mknod 2 ,
.Xr mmap 2 ,
.Xr read 2
and
.Xr utimes 2
system calls.
.It Fa st_mtim
Time when file data last modified.
Changed by the
.Xr mknod 2 ,
.Xr utimes 2
and
.Xr write 2
system calls.
.It Fa st_ctim
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
For compatibility with earlier versions of the
.Tn POSIX
standard, the following macros are defined:
.Bd -literal
#define st_atime st_atim.tv_sec
#define st_mtime st_mtim.tv_sec
#define st_ctime st_ctim.tv_sec
.Ed
.Pp
The size-related fields of the
.Vt struct stat
are as follows:
.Bl -tag -width ".Fa st_blksize"
.It Fa st_blksize
The optimal I/O block size for the file.
.It Fa 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
.In 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
.Fa st_dev ,
.Fa st_uid ,
.Fa st_gid ,
.Fa st_rdev ,
.Fa st_size ,
.Fa st_blksize
and
.Fa st_blocks
fields.
.Sh ERRORS
.Fn Stat
and
.Fn lstat
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 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 EFAULT
.Fa sb
or
.Em name
points to an invalid address.
.El
.Pp
.Fn Fstat
will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
.Fa fd
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 occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr access 2 ,
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr statfs 2 ,
.Xr statvfs 2 ,
.Xr utimes 2 ,
.Xr symlink 7
.Sh STANDARDS
The
.Fn stat
and
.Fn fstat
system calls are expected to conform to
.St -p1003.1-90 .
.Sh HISTORY
A
.Fn stat
and a
.Fn fstat
system call appeared in
.At v7 .
A
.Fn lstat
system call appeared in
.Bx 4.2 .
The
.Fn fstatat
system call appeared in
.Dx 2.3 .
.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.