509124b626
It is currently allowed to fchownat(2), fchmodat(2), fchflagsat(2), utimensat(2), fstatat(2), and linkat(2). For linkat(2), PRIV_VFS_FHOPEN privilege is required to exercise the flag. It allows to link any open file. Requested by: trasz Tested by: pho, trasz Reviewed by: markj Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D29111
493 lines
11 KiB
Groff
493 lines
11 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993, 1994
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)stat.2 8.4 (Berkeley) 5/1/95
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.\" $FreeBSD$
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.\"
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.Dd March 30, 2021
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.Dt STAT 2
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.Os
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.Sh NAME
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.Nm stat ,
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.Nm lstat ,
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.Nm fstat ,
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.Nm fstatat
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.Nd get file status
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/stat.h
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.Ft int
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.Fn stat "const char * restrict path" "struct stat * restrict sb"
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.Ft int
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.Fn lstat "const char * restrict path" "struct stat * restrict sb"
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.Ft int
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.Fn fstat "int fd" "struct stat *sb"
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.Ft int
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.Fn fstatat "int fd" "const char *path" "struct stat *sb" "int flag"
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.Sh DESCRIPTION
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The
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.Fn stat
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system call obtains information about the file pointed to by
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.Fa path .
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Read, write or execute
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permission of the named file is not required, but all directories
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listed in the path name leading to the file must be searchable.
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.Pp
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The
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.Fn lstat
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system call is like
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.Fn stat
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except when the named file is a symbolic link,
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in which case
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.Fn lstat
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returns information about the link,
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while
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.Fn stat
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returns information about the file the link references.
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.Pp
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The
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.Fn fstat
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system call obtains the same information about an open file
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known by the file descriptor
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.Fa fd .
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.Pp
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The
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.Fn fstatat
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system call is equivalent to
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.Fn stat
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and
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.Fn lstat
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except when the
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.Fa path
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specifies a relative path.
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For
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.Fn fstatat
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and relative
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.Fa path ,
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the status is retrieved from a file relative to
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the directory associated with the file descriptor
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.Fa fd
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instead of the current working directory.
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.Pp
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The values for the
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.Fa flag
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are constructed by a bitwise-inclusive OR of flags from this list,
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defined in
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.In fcntl.h :
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.Bl -tag -width indent
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.It Dv AT_SYMLINK_NOFOLLOW
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If
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.Fa path
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names a symbolic link, the status of the symbolic link is returned.
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.It Dv AT_RESOLVE_BENEATH
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Only walk paths below the starting directory.
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See the description of the
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.Dv O_RESOLVE_BENEATH
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flag in the
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.Xr open 2
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manual page.
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.It Dv AT_EMPTY_PATH
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If the
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.Fa path
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argument is an empty string, operate on the file or directory
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referenced by the descriptor
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.Fa fd .
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If
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.Fa fd
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is equal to
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.Dv AT_FDCWD ,
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operate on the current working directory.
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.El
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.Pp
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If
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.Fn fstatat
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is passed the special value
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.Dv AT_FDCWD
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in the
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.Fa fd
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parameter, the current working directory is used and the behavior is
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identical to a call to
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.Fn stat
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or
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.Fn lstat
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respectively, depending on whether or not the
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.Dv AT_SYMLINK_NOFOLLOW
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bit is set in
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.Fa flag .
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.Pp
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When
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.Fn fstatat
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is called with an absolute
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.Fa path ,
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it ignores the
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.Fa fd
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argument.
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.Pp
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The
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.Fa sb
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argument is a pointer to a
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.Vt stat
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structure
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as defined by
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.In sys/stat.h
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and into which information is placed concerning the file.
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.Pp
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The fields of
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.Vt "struct stat"
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related to the file system are:
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.Bl -tag -width ".Va st_nlink"
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.It Va st_dev
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Numeric ID of the device containing the file.
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.It Va st_ino
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The file's inode number.
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.It Va st_nlink
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Number of hard links to the file.
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.It Va st_flags
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Flags enabled for the file.
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See
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.Xr chflags 2
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for the list of flags and their description.
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.El
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.Pp
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The
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.Va st_dev
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and
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.Va st_ino
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fields together identify the file uniquely within the system.
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.Pp
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The time-related fields of
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.Vt "struct stat"
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are:
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.Bl -tag -width ".Va st_birthtim"
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.It Va st_atim
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Time when file data was last accessed.
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Changed implicitly by syscalls such as
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.Xr read 2
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and
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.Xr readv 2 ,
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and explicitly by
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.Xr utimes 2 .
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.It Va st_mtim
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Time when file data was last modified.
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Changed implicitly by syscalls such as
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.Xr truncate 2 ,
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.Xr write 2 ,
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and
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.Xr writev 2 ,
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and explicitly by
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.Xr utimes 2 .
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Also, any syscall which modifies directory content changes the
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.Va st_mtim
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for the affected directory.
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For instance,
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.Xr creat 2 ,
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.Xr mkdir 2 ,
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.Xr rename 2 ,
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.Xr link 2 ,
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and
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.Xr unlink 2 .
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.It Va st_ctim
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Time when file status was last changed (inode data modification).
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Changed implicitly by any syscall that affects file metadata, including
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.Va st_mtim ,
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such as
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.Xr chflags 2 ,
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.Xr chmod 2 ,
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.Xr chown 2 ,
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.Xr truncate 2 ,
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.Xr utimes 2 ,
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and
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.Xr write 2 .
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Also, any syscall which modifies directory content changes the
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.Va st_ctim
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for the affected directory.
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For instance,
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.Xr creat 2 ,
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.Xr mkdir 2 ,
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.Xr rename 2 ,
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.Xr link 2 ,
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and
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.Xr unlink 2 .
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.It Va st_birthtim
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Time when the inode was created.
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.El
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.Pp
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These time-related macros are defined for compatibility:
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.Bd -literal
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#define st_atime st_atim.tv_sec
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#define st_mtime st_mtim.tv_sec
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#define st_ctime st_ctim.tv_sec
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#ifndef _POSIX_SOURCE
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#define st_birthtime st_birthtim.tv_sec
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#endif
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#ifndef _POSIX_SOURCE
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#define st_atimespec st_atim
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#define st_mtimespec st_mtim
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#define st_ctimespec st_ctim
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#define st_birthtimespec st_birthtim
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#endif
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.Ed
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.Pp
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Size-related fields of the
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.Vt "struct stat"
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are:
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.Bl -tag -width ".Va st_blksize"
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.It Va st_size
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File size in bytes.
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.It Va st_blksize
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Optimal I/O block size for the file.
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.It Va st_blocks
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Actual number of blocks allocated for the file in 512-byte units.
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As short symbolic links are stored in the inode, this number may
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be zero.
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.El
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.Pp
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The access-related fields of
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.Vt "struct stat"
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are:
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.Bl -tag -width ".Va st_mode"
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.It Va st_uid
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User ID of the file's owner.
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.It Va st_gid
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Group ID of the file.
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.It Va st_mode
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Status of the file (see below).
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.El
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.Pp
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The status information word
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.Fa st_mode
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has these bits:
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.Bd -literal
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#define S_IFMT 0170000 /* type of file mask */
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#define S_IFIFO 0010000 /* named pipe (fifo) */
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#define S_IFCHR 0020000 /* character special */
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#define S_IFDIR 0040000 /* directory */
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#define S_IFBLK 0060000 /* block special */
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#define S_IFREG 0100000 /* regular */
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#define S_IFLNK 0120000 /* symbolic link */
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#define S_IFSOCK 0140000 /* socket */
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#define S_IFWHT 0160000 /* whiteout */
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#define S_ISUID 0004000 /* set user id on execution */
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#define S_ISGID 0002000 /* set group id on execution */
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#define S_ISVTX 0001000 /* save swapped text even after use */
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#define S_IRWXU 0000700 /* RWX mask for owner */
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#define S_IRUSR 0000400 /* read permission, owner */
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#define S_IWUSR 0000200 /* write permission, owner */
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#define S_IXUSR 0000100 /* execute/search permission, owner */
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#define S_IRWXG 0000070 /* RWX mask for group */
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#define S_IRGRP 0000040 /* read permission, group */
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#define S_IWGRP 0000020 /* write permission, group */
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#define S_IXGRP 0000010 /* execute/search permission, group */
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#define S_IRWXO 0000007 /* RWX mask for other */
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#define S_IROTH 0000004 /* read permission, other */
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#define S_IWOTH 0000002 /* write permission, other */
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#define S_IXOTH 0000001 /* execute/search permission, other */
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.Ed
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.Pp
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For a list of access modes, see
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.In sys/stat.h ,
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.Xr access 2
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and
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.Xr chmod 2 .
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These macros are available to test whether a
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.Va st_mode
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value passed in the
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.Fa m
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argument corresponds to a file of the specified type:
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.Bl -tag -width ".Fn S_ISFIFO m"
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.It Fn S_ISBLK m
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Test for a block special file.
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.It Fn S_ISCHR m
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Test for a character special file.
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.It Fn S_ISDIR m
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Test for a directory.
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.It Fn S_ISFIFO m
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Test for a pipe or FIFO special file.
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.It Fn S_ISLNK m
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Test for a symbolic link.
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.It Fn S_ISREG m
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Test for a regular file.
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.It Fn S_ISSOCK m
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Test for a socket.
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.It Fn S_ISWHT m
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Test for a whiteout.
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.El
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.Pp
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The macros evaluate to a non-zero value if the test is true
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or to the value 0 if the test is false.
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.Sh RETURN VALUES
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.Rv -std
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.Sh COMPATIBILITY
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Previous versions of the system used different types for the
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.Va st_dev ,
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.Va st_uid ,
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.Va st_gid ,
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.Va st_rdev ,
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.Va st_size ,
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.Va st_blksize
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and
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.Va st_blocks
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fields.
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.Sh ERRORS
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The
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.Fn stat
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and
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.Fn lstat
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system calls will fail if:
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.Bl -tag -width Er
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.It Bq Er EACCES
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Search permission is denied for a component of the path prefix.
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.It Bq Er EFAULT
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The
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.Fa sb
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or
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.Fa path
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argument
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points to an invalid address.
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.It Bq Er EIO
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An I/O error occurred while reading from or writing to the file system.
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.It Bq Er EINTEGRITY
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Corrupted data was detected while reading from the file system.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded 255 characters,
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or an entire path name exceeded 1023 characters.
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.It Bq Er ENOENT
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The named file does not exist.
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.It Bq Er ENOTDIR
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A component of the path prefix is not a directory.
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.It Bq Er EOVERFLOW
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The file size in bytes cannot be
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represented correctly in the structure pointed to by
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.Fa sb .
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.El
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.Pp
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The
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.Fn fstat
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system call will fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa fd
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argument
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is not a valid open file descriptor.
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.It Bq Er EFAULT
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The
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.Fa sb
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argument
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points to an invalid address.
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.It Bq Er EIO
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An I/O error occurred while reading from or writing to the file system.
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.It Bq Er EINTEGRITY
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Corrupted data was detected while reading from the file system.
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.It Bq Er EOVERFLOW
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The file size in bytes cannot be
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represented correctly in the structure pointed to by
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.Fa sb .
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.El
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.Pp
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In addition to the errors returned by the
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.Fn lstat ,
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the
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.Fn fstatat
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may fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa path
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argument does not specify an absolute path and the
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.Fa fd
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argument is neither
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.Dv AT_FDCWD
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nor a valid file descriptor open for searching.
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.It Bq Er EINVAL
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The value of the
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.Fa flag
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argument is not valid.
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.It Bq Er ENOTDIR
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The
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.Fa path
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argument is not an absolute path and
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.Fa fd
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is neither
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.Dv AT_FDCWD
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nor a file descriptor associated with a directory.
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.It Bq Er ENOTCAPABLE
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.Fa path
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is an absolute path,
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or contained a ".." component leading to a
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directory outside of the directory hierarchy specified by
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.Fa fd ,
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and the process is in capability mode or the
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.Dv AT_RESOLVE_BENEATH
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flag was specified.
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.El
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.Sh SEE ALSO
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|
.Xr access 2 ,
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.Xr chmod 2 ,
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.Xr chown 2 ,
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.Xr fhstat 2 ,
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.Xr statfs 2 ,
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.Xr utimes 2 ,
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.Xr sticky 7 ,
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.Xr symlink 7
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.Sh STANDARDS
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The
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.Fn stat
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and
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.Fn fstat
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system calls are expected to conform to
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.St -p1003.1-90 .
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The
|
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.Fn fstatat
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system call follows The Open Group Extended API Set 2 specification.
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.Sh HISTORY
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|
The
|
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.Fn stat
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and
|
|
.Fn fstat
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system calls appeared in
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.At v1 .
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The
|
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.Fn lstat
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system call appeared in
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.Bx 4.2 .
|
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The
|
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.Fn fstatat
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system call appeared in
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.Fx 8.0 .
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.Sh BUGS
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|
Applying
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.Fn fstat
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to a socket
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returns a zeroed buffer,
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except for the blocksize field,
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and a unique device and inode number.
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