5b1fb8ec66
paths. It was decided that committing the code and drafting of the man page update is better than allowing the code to rot until wordsmithing happens. Reviewed by: jilles (previous version) Discussed with: brooks, jilles, emaste Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D17714
354 lines
9.3 KiB
Groff
354 lines
9.3 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
|
|
.\" 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.
|
|
.\"
|
|
.\" @(#)chmod.2 8.1 (Berkeley) 6/4/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd November 11, 2018
|
|
.Dt CHMOD 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm chmod ,
|
|
.Nm fchmod ,
|
|
.Nm lchmod ,
|
|
.Nm fchmodat
|
|
.Nd change mode of file
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In sys/stat.h
|
|
.Ft int
|
|
.Fn chmod "const char *path" "mode_t mode"
|
|
.Ft int
|
|
.Fn fchmod "int fd" "mode_t mode"
|
|
.Ft int
|
|
.Fn lchmod "const char *path" "mode_t mode"
|
|
.Ft int
|
|
.Fn fchmodat "int fd" "const char *path" "mode_t mode" "int flag"
|
|
.Sh DESCRIPTION
|
|
The file permission bits of the file named specified by
|
|
.Fa path
|
|
or referenced by the file descriptor
|
|
.Fa fd
|
|
are changed to
|
|
.Fa mode .
|
|
The
|
|
.Fn chmod
|
|
system call verifies that the process owner (user) either owns
|
|
the file specified by
|
|
.Fa path
|
|
(or
|
|
.Fa fd ) ,
|
|
or
|
|
is the super-user.
|
|
The
|
|
.Fn chmod
|
|
system call follows symbolic links to operate on the target of the link
|
|
rather than the link itself.
|
|
.Pp
|
|
The
|
|
.Fn lchmod
|
|
system call is similar to
|
|
.Fn chmod
|
|
but does not follow symbolic links.
|
|
.Pp
|
|
The
|
|
.Fn fchmodat
|
|
is equivalent to either
|
|
.Fn chmod
|
|
or
|
|
.Fn lchmod
|
|
depending on the
|
|
.Fa flag
|
|
except in the case where
|
|
.Fa path
|
|
specifies a relative path.
|
|
In this case the file to be changed is determined relative to the directory
|
|
associated with the file descriptor
|
|
.Fa fd
|
|
instead of the current working directory.
|
|
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, then the mode of the symbolic link is changed.
|
|
.It Dv AT_BENEATH
|
|
Only allow to change permissions of a file which is beneath of
|
|
the topping directory.
|
|
See the description of the
|
|
.Dv O_BENEATH
|
|
flag in the
|
|
.Xr open 2
|
|
manual page.
|
|
.El
|
|
.Pp
|
|
If
|
|
.Fn fchmodat
|
|
is passed the special value
|
|
.Dv AT_FDCWD
|
|
in the
|
|
.Fa fd
|
|
parameter, the current working directory is used.
|
|
If also
|
|
.Fa flag
|
|
is zero, the behavior is identical to a call to
|
|
.Fn chmod .
|
|
.Pp
|
|
A mode is created from
|
|
.Em or'd
|
|
permission bit masks
|
|
defined in
|
|
.In sys/stat.h :
|
|
.Pp
|
|
.Bd -literal -offset indent -compact
|
|
#define S_IRWXU 0000700 /* RWX mask for owner */
|
|
#define S_IRUSR 0000400 /* R for owner */
|
|
#define S_IWUSR 0000200 /* W for owner */
|
|
#define S_IXUSR 0000100 /* X for owner */
|
|
|
|
#define S_IRWXG 0000070 /* RWX mask for group */
|
|
#define S_IRGRP 0000040 /* R for group */
|
|
#define S_IWGRP 0000020 /* W for group */
|
|
#define S_IXGRP 0000010 /* X for group */
|
|
|
|
#define S_IRWXO 0000007 /* RWX mask for other */
|
|
#define S_IROTH 0000004 /* R for other */
|
|
#define S_IWOTH 0000002 /* W for other */
|
|
#define S_IXOTH 0000001 /* X for other */
|
|
|
|
#define S_ISUID 0004000 /* set user id on execution */
|
|
#define S_ISGID 0002000 /* set group id on execution */
|
|
#define S_ISVTX 0001000 /* sticky bit */
|
|
.Ed
|
|
.Pp
|
|
The non-standard
|
|
.Dv S_ISTXT
|
|
is a synonym for
|
|
.Dv S_ISVTX .
|
|
.Pp
|
|
The
|
|
.Fx
|
|
VM system totally ignores the sticky bit
|
|
.Pq Dv S_ISVTX
|
|
for executables.
|
|
On UFS-based file systems (FFS, LFS) the sticky
|
|
bit may only be set upon directories.
|
|
.Pp
|
|
If mode
|
|
.Dv S_ISVTX
|
|
(the `sticky bit') is set on a directory,
|
|
an unprivileged user may not delete or rename
|
|
files of other users in that directory.
|
|
The sticky bit may be
|
|
set by any user on a directory which the user owns or has appropriate
|
|
permissions.
|
|
For more details of the properties of the sticky bit, see
|
|
.Xr sticky 7 .
|
|
.Pp
|
|
If mode ISUID (set UID) is set on a directory,
|
|
and the MNT_SUIDDIR option was used in the mount of the file system,
|
|
then the owner of any new files and sub-directories
|
|
created within this directory are set
|
|
to be the same as the owner of that directory.
|
|
If this function is enabled, new directories will inherit
|
|
the bit from their parents.
|
|
Execute bits are removed from
|
|
the file, and it will not be given to root.
|
|
This behavior does not change the
|
|
requirements for the user to be allowed to write the file, but only the eventual
|
|
owner after it has been created.
|
|
Group inheritance is not affected.
|
|
.Pp
|
|
This feature is designed for use on fileservers serving PC users via
|
|
ftp, SAMBA, or netatalk.
|
|
It provides security holes for shell users and as
|
|
such should not be used on shell machines, especially on home directories.
|
|
This option requires the SUIDDIR
|
|
option in the kernel to work.
|
|
Only UFS file systems support this option.
|
|
For more details of the suiddir mount option, see
|
|
.Xr mount 8 .
|
|
.Pp
|
|
Writing or changing the owner of a file
|
|
turns off the set-user-id and set-group-id bits
|
|
unless the user is the super-user.
|
|
This makes the system somewhat more secure
|
|
by protecting set-user-id (set-group-id) files
|
|
from remaining set-user-id (set-group-id) if they are modified,
|
|
at the expense of a degree of compatibility.
|
|
.Sh RETURN VALUES
|
|
.Rv -std
|
|
.Sh ERRORS
|
|
The
|
|
.Fn chmod
|
|
system call
|
|
will fail and the file mode will be unchanged if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er ENOTDIR
|
|
A component of the path prefix is not a directory.
|
|
.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 EPERM
|
|
The effective user ID does not match the owner of the file and
|
|
the effective user ID is not the super-user.
|
|
.It Bq Er EPERM
|
|
The effective user ID is not the super-user, the effective user ID do match the
|
|
owner of the file, but the group ID of the file does not match the effective
|
|
group ID nor one of the supplementary group IDs.
|
|
.It Bq Er EPERM
|
|
The named file has its immutable or append-only flag set, see the
|
|
.Xr chflags 2
|
|
manual page for more information.
|
|
.It Bq Er EROFS
|
|
The named file resides on a read-only file system.
|
|
.It Bq Er EFAULT
|
|
The
|
|
.Fa path
|
|
argument
|
|
points outside the process's allocated address space.
|
|
.It Bq Er EIO
|
|
An I/O error occurred while reading from or writing to the file system.
|
|
.It Bq Er EFTYPE
|
|
The effective user ID is not the super-user, the mode includes the sticky bit
|
|
.Dv ( S_ISVTX ) ,
|
|
and path does not refer to a directory.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn fchmod
|
|
system call will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EBADF
|
|
The descriptor is not valid.
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa fd
|
|
argument
|
|
refers to a socket, not to a file.
|
|
.It Bq Er EROFS
|
|
The file resides on a read-only file system.
|
|
.It Bq Er EIO
|
|
An I/O error occurred while reading from or writing to the file system.
|
|
.El
|
|
.Pp
|
|
In addition to the
|
|
.Fn chmod
|
|
errors,
|
|
.Fn fchmodat
|
|
fails if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EBADF
|
|
The
|
|
.Fa path
|
|
argument does not specify an absolute path and the
|
|
.Fa fd
|
|
argument is neither
|
|
.Fa AT_FDCWD
|
|
nor a valid file descriptor open for searching.
|
|
.It Bq Er EINVAL
|
|
The value of the
|
|
.Fa flag
|
|
argument is not valid.
|
|
.It Bq Er ENOTDIR
|
|
The
|
|
.Fa path
|
|
argument is not an absolute path and
|
|
.Fa fd
|
|
is neither
|
|
.Dv AT_FDCWD
|
|
nor a file descriptor associated with a directory.
|
|
.It Bq Er ENOTCAPABLE
|
|
.Fa path
|
|
is an absolute path,
|
|
or contained a ".." component leading to a
|
|
directory outside of the directory hierarchy specified by
|
|
.Fa fd ,
|
|
and the process is in capability mode.
|
|
.It Bq Er ENOTCAPABLE
|
|
The
|
|
.Dv AT_BENEATH
|
|
flag was provided to
|
|
.Fn fchmodat ,
|
|
and the absolute
|
|
.Fa path
|
|
does not have its tail fully contained under the topping directory,
|
|
or the relative
|
|
.Fa path
|
|
escapes it.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr chmod 1 ,
|
|
.Xr chflags 2 ,
|
|
.Xr chown 2 ,
|
|
.Xr open 2 ,
|
|
.Xr stat 2 ,
|
|
.Xr sticky 7
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn chmod
|
|
system call is expected to conform to
|
|
.St -p1003.1-90 ,
|
|
except for the return of
|
|
.Er EFTYPE .
|
|
The
|
|
.Dv S_ISVTX
|
|
bit on directories is expected to conform to
|
|
.St -susv3 .
|
|
The
|
|
.Fn fchmodat
|
|
system call is expected to conform to
|
|
.St -p1003.1-2008 .
|
|
.Sh HISTORY
|
|
The
|
|
.Fn chmod
|
|
function appeared in
|
|
.At v1 .
|
|
The
|
|
.Fn fchmod
|
|
system call appeared in
|
|
.Bx 4.2 .
|
|
The
|
|
.Fn lchmod
|
|
system call appeared in
|
|
.Fx 3.0 .
|
|
The
|
|
.Fn fchmodat
|
|
system call appeared in
|
|
.Fx 8.0 .
|