2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
248 lines
7 KiB
Groff
248 lines
7 KiB
Groff
.\" $NetBSD: chmod.2,v 1.37 2010/05/31 12:16:20 njoly Exp $
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.\"
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.\" Copyright (c) 1980, 1991, 1993
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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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.\" @(#)chmod.2 8.1 (Berkeley) 6/4/93
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.\"
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.Dd January 4, 2009
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.Dt CHMOD 2
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.Os
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.Sh NAME
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.Nm chmod ,
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.Nm lchmod ,
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.Nm fchmod
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.Nd change mode of file
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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 chmod "const char *path" "mode_t mode"
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.Ft int
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.Fn lchmod "const char *path" "mode_t mode"
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.Ft int
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.Fn fchmod "int fd" "mode_t mode"
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.Sh DESCRIPTION
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The function
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.Fn chmod
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sets the file permission bits
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of the file
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specified by the pathname
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.Fa path
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to
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.Fa mode .
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.Fn fchmod
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sets the permission bits of the specified
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file descriptor
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.Fa fd .
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.Fn lchmod
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is like
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.Fn chmod
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except in the case where the named file is a symbolic link,
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in which case
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.Fn lchmod
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sets the permission bits of the link,
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while
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.Fn chmod
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sets the bits of the file the link references.
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.Fn chmod
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verifies that the process owner (user) either owns
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the file specified by
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.Fa path
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(or
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.Fa fd ) ,
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or
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is the super-user.
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A mode is created from
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.Em or'd
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permission bit masks
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defined in
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.In sys/stat.h :
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.Bd -literal -offset indent -compact
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#define S_IRWXU 0000700 /* RWX mask for owner */
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#define S_IRUSR 0000400 /* R for owner */
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#define S_IWUSR 0000200 /* W for owner */
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#define S_IXUSR 0000100 /* X for owner */
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#define S_IRWXG 0000070 /* RWX mask for group */
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#define S_IRGRP 0000040 /* R for group */
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#define S_IWGRP 0000020 /* W for group */
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#define S_IXGRP 0000010 /* X for group */
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#define S_IRWXO 0000007 /* RWX mask for other */
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#define S_IROTH 0000004 /* R for other */
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#define S_IWOTH 0000002 /* W for other */
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#define S_IXOTH 0000001 /* X for other */
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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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.Ed
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.Pp
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If mode
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.Dv ISVTX
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(the
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.Sq sticky bit )
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is set on a regular file, it historically meant that the system should
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save a shareable copy of the program text in the swap area.
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When applied to commonly used programs like the shell or editor, this
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would decrease memory usage and startup time.
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In
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.Nx ,
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the sticky bit may still be set on regular files by the super-user,
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but has no effect.
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The historical meaning became obsolete in the 1980s with the advent of
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memory-mapped executables, and is only documented as a matter of
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historical interest.
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.Pp
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If mode
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.Dv ISVTX
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(the
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.Sq sticky bit )
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is set on a directory,
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an unprivileged user may not delete or rename
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files of other users in that directory.
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The sticky bit may be set by any user on a directory which the user
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owns or has appropriate permissions.
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.Pp
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For more information about the properties of the sticky bit, see
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.Xr sticky 7 .
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.Pp
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Changing the owner of a file
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turns off the set-user-id and set-group-id bits;
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writing to a file
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turns off the set-user-id and set-group-id bits
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unless the user is the super-user.
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This makes the system somewhat more secure
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by protecting set-user-id (set-group-id) files
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from remaining set-user-id (set-group-id) if they are modified,
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at the expense of a degree of compatibility.
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.Sh RETURN VALUES
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Upon successful completion, a value of 0 is returned.
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Otherwise, a value of \-1 is returned and
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Fn chmod
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and
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.Fn lchmod
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will fail and the file mode will be unchanged if:
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.Bl -tag -width Er
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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 ENAMETOOLONG
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A component of a pathname exceeded
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.Brq Dv NAME_MAX
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characters, or an entire path name exceeded
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.Brq Dv PATH_MAX
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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 EACCES
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Search permission is denied for a component of the path prefix.
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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 EPERM
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The effective user ID does not match the owner of the file and
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the effective user ID is not the super-user.
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.It Bq Er EPERM
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The mode includes the setgid bit
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.Pq Dv S_ISGID
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but the file's group is neither the effective group ID nor is it in the
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group access list.
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.It Bq Er EROFS
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The named file resides on a read-only file system.
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.It Bq Er EFAULT
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.Fa path
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points outside the process's allocated address space.
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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 EFTYPE
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The effective user ID is not the super-user, the
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.Fa mode
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includes the sticky bit
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.Pq Dv S_ISVTX ,
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and
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.Fa path
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does not refer to a directory.
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.El
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.Pp
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.Fn fchmod
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The descriptor is not valid.
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.It Bq Er EINVAL
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.Fa fd
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refers to a socket, not to a file.
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.It Bq Er EPERM
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The effective user ID does not match the owner of the file and
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the effective user ID is not the super-user.
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.It Bq Er EPERM
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The mode includes the setgid bit
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.Pq Dv S_ISGID
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but the file's group is neither the effective group ID nor is it in the
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group access list.
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.It Bq Er EROFS
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The file resides on a read-only file system.
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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 EFTYPE
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The effective user ID is not the super-user, the
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.Fa mode
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includes the sticky bit
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.Pq Dv S_ISVTX ,
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and
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.Fa fd
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does not refer to a directory.
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.El
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.Sh SEE ALSO
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.Xr chmod 1 ,
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.Xr chflags 2 ,
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.Xr chown 2 ,
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.Xr open 2 ,
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.Xr stat 2 ,
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.Xr getmode 3 ,
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.Xr setmode 3 ,
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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 chmod
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function conforms to
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.St -p1003.1-90 .
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.Sh HISTORY
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The
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.Fn fchmod
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function call
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appeared in
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.Bx 4.2 .
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The
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.Fn lchmod
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function call appeared in
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.Nx 1.3 .
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