+++ /dev/null
-.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
-.\" and Copyright (c) 1998 Andries Brouwer (aeb@cwi.nl)
-.\" and Copyright (c) 2006, 2007, 2008, 2014 Michael Kerrisk <mtk.manpages@gmail.com>
-.\"
-.\" %%%LICENSE_START(VERBATIM)
-.\" Permission is granted to make and distribute verbatim copies of this
-.\" manual provided the copyright notice and this permission notice are
-.\" preserved on all copies.
-.\"
-.\" Permission is granted to copy and distribute modified versions of this
-.\" manual under the conditions for verbatim copying, provided that the
-.\" entire resulting derived work is distributed under the terms of a
-.\" permission notice identical to this one.
-.\"
-.\" Since the Linux kernel and libraries are constantly changing, this
-.\" manual page may be incorrect or out-of-date. The author(s) assume no
-.\" responsibility for errors or omissions, or for damages resulting from
-.\" the use of the information contained herein. The author(s) may not
-.\" have taken the same level of care in the production of this manual,
-.\" which is licensed free of charge, as they might when working
-.\" professionally.
-.\"
-.\" Formatted or processed versions of this manual, if unaccompanied by
-.\" the source, must acknowledge the copyright and authors of this work.
-.\" %%%LICENSE_END
-.\"
-.\" Modified by Michael Haardt <michael@moria.de>
-.\" Modified 1993-07-21 by Rik Faith <faith@cs.unc.edu>
-.\" Modified 1996-07-09 by Andries Brouwer <aeb@cwi.nl>
-.\" Modified 1996-11-06 by Eric S. Raymond <esr@thyrsus.com>
-.\" Modified 1997-05-18 by Michael Haardt <michael@cantor.informatik.rwth-aachen.de>
-.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
-.\" 2007-07-08, mtk, added an example program; updated SYNOPSIS
-.\" 2008-05-08, mtk, Describe rules governing ownership of new files
-.\" (bsdgroups versus sysvgroups, and the effect of the parent
-.\" directory's set-group-ID permission bit).
-.\"
-.TH CHOWN 2 2014-08-19 "Linux" "Linux Programmer's Manual"
-.SH NAME
-chown, fchown, lchown, fchownat \- change ownership of a file
-.SH SYNOPSIS
-.nf
-.B #include <unistd.h>
-.sp
-.BI "int chown(const char *" pathname ", uid_t " owner ", gid_t " group );
-.br
-.BI "int fchown(int " fd ", uid_t " owner ", gid_t " group );
-.br
-.BI "int lchown(const char *" pathname ", uid_t " owner ", gid_t " group );
-.sp
-.BR "#include <fcntl.h> " "/* Definition of AT_* constants */"
-.B #include <unistd.h>
-.sp
-.BI "int fchownat(int " dirfd ", const char *" pathname ,
-.BI " uid_t " owner ", gid_t " group ", int " flags );
-.fi
-.sp
-.sp
-.in -4n
-Feature Test Macro Requirements for glibc (see
-.BR feature_test_macros (7)):
-.in
-.sp
-.BR fchown (),
-.BR lchown ():
-.PD 0
-.ad l
-.RS 4
-_BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
-_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
-.br
-|| /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
-.RE
-.sp
-.BR fchownat ():
-.PD 0
-.ad l
-.RS 4
-.TP 4
-Since glibc 2.10:
-_XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
-.TP
-Before glibc 2.10:
-_ATFILE_SOURCE
-.RE
-.ad
-.PD
-.SH DESCRIPTION
-These system calls change the owner and group of a file.
-The
-.BR chown (),
-.BR fchown (),
-and
-.BR lchown ()
-system calls differ only in how the file is specified:
-.IP * 2
-.BR chown ()
-changes the ownership of the file specified by
-.IR pathname ,
-which is dereferenced if it is a symbolic link.
-.IP *
-.BR fchown ()
-changes the ownership of the file referred to by the open file descriptor
-.IR fd .
-.IP *
-.BR lchown ()
-is like
-.BR chown (),
-but does not dereference symbolic links.
-.PP
-Only a privileged process (Linux: one with the
-.B CAP_CHOWN
-capability) may change the owner of a file.
-The owner of a file may change the group of the file
-to any group of which that owner is a member.
-A privileged process (Linux: with
-.BR CAP_CHOWN )
-may change the group arbitrarily.
-
-If the
-.I owner
-or
-.I group
-is specified as \-1, then that ID is not changed.
-
-When the owner or group of an executable file are
-changed by an unprivileged user the
-.B S_ISUID
-and
-.B S_ISGID
-mode bits are cleared.
-POSIX does not specify whether
-this also should happen when root does the
-.BR chown ();
-the Linux behavior depends on the kernel version.
-.\" In Linux 2.0 kernels, superuser was like everyone else
-.\" In 2.2, up to 2.2.12, these bits were not cleared for superuser.
-.\" Since 2.2.13, superuser is once more like everyone else.
-In case of a non-group-executable file (i.e., one for which the
-.B S_IXGRP
-bit is not set) the
-.B S_ISGID
-bit indicates mandatory locking, and is not cleared by a
-.BR chown ().
-.SS fchownat()
-The
-.BR fchownat ()
-system call operates in exactly the same way as
-.BR chown (),
-except for the differences described here.
-
-If the pathname given in
-.I pathname
-is relative, then it is interpreted relative to the directory
-referred to by the file descriptor
-.I dirfd
-(rather than relative to the current working directory of
-the calling process, as is done by
-.BR chown ()
-for a relative pathname).
-
-If
-.I pathname
-is relative and
-.I dirfd
-is the special value
-.BR AT_FDCWD ,
-then
-.I pathname
-is interpreted relative to the current working
-directory of the calling process (like
-.BR chown ()).
-
-If
-.I pathname
-is absolute, then
-.I dirfd
-is ignored.
-
-The
-.I flags
-argument is a bit mask created by ORing together
-0 or more of the following values;
-.TP
-.BR AT_EMPTY_PATH " (since Linux 2.6.39)"
-.\" commit 65cfc6722361570bfe255698d9cd4dccaf47570d
-If
-.I pathname
-is an empty string, operate on the file referred to by
-.IR dirfd
-(which may have been obtained using the
-.BR open (2)
-.B O_PATH
-flag).
-In this case,
-.I dirfd
-can refer to any type of file, not just a directory.
-If
-.I dirfd
-is
-.BR AT_FDCWD ,
-the call operates on the current working directory.
-This flag is Linux-specific; define
-.B _GNU_SOURCE
-.\" Before glibc 2.16, defining _ATFILE_SOURCE sufficed
-to obtain its definition.
-
-.TP
-.B AT_SYMLINK_NOFOLLOW
-If
-.I pathname
-is a symbolic link, do not dereference it:
-instead operate on the link itself, like
-.BR lchown ().
-(By default,
-.BR fchownat ()
-dereferences symbolic links, like
-.BR chown ().)
-.PP
-See
-.BR openat (2)
-for an explanation of the need for
-.BR fchownat ().
-.SH RETURN VALUE
-On success, zero is returned.
-On error, \-1 is returned, and
-.I errno
-is set appropriately.
-.SH ERRORS
-Depending on the filesystem,
-errors other than those listed below can be returned.
-
-The more general errors for
-.BR chown ()
-are listed below.
-.TP
-.B EACCES
-Search permission is denied on a component of the path prefix.
-(See also
-.BR path_resolution (7).)
-.TP
-.B EFAULT
-.I pathname
-points outside your accessible address space.
-.TP
-.B ELOOP
-Too many symbolic links were encountered in resolving
-.IR pathname .
-.TP
-.B ENAMETOOLONG
-.I pathname
-is too long.
-.TP
-.B ENOENT
-The file does not exist.
-.TP
-.B ENOMEM
-Insufficient kernel memory was available.
-.TP
-.B ENOTDIR
-A component of the path prefix is not a directory.
-.TP
-.B EPERM
-The calling process did not have the required permissions
-(see above) to change owner and/or group.
-.TP
-.B EROFS
-The named file resides on a read-only filesystem.
-.PP
-The general errors for
-.BR fchown ()
-are listed below:
-.TP
-.B EBADF
-The descriptor is not valid.
-.TP
-.B EIO
-A low-level I/O error occurred while modifying the inode.
-.TP
-.B ENOENT
-See above.
-.TP
-.B EPERM
-See above.
-.TP
-.B EROFS
-See above.
-.PP
-The same errors that occur for
-.BR chown ()
-can also occur for
-.BR fchownat ().
-The following additional errors can occur for
-.BR fchownat ():
-.TP
-.B EBADF
-.I dirfd
-is not a valid file descriptor.
-.TP
-.B EINVAL
-Invalid flag specified in
-.IR flags .
-.TP
-.B ENOTDIR
-.I pathname
-is relative and
-.I dirfd
-is a file descriptor referring to a file other than a directory.
-.SH VERSIONS
-.BR fchownat ()
-was added to Linux in kernel 2.6.16;
-library support was added to glibc in version 2.4.
-.SH CONFORMING TO
-.BR chown (),
-.BR fchown (),
-.BR lchown ():
-4.4BSD, SVr4, POSIX.1-2001, POSIX.1-2008.
-
-The 4.4BSD version can be
-used only by the superuser (that is, ordinary users cannot give away files).
-.\" chown():
-.\" SVr4 documents EINVAL, EINTR, ENOLINK and EMULTIHOP returns, but no
-.\" ENOMEM. POSIX.1 does not document ENOMEM or ELOOP error conditions.
-.\" fchown():
-.\" SVr4 documents additional EINVAL, EIO, EINTR, and ENOLINK
-.\" error conditions.
-
-.BR fchownat ():
-POSIX.1-2008.
-.SH NOTES
-.SS Ownership of new files
-When a new file is created (by, for example,
-.BR open (2)
-or
-.BR mkdir (2)),
-its owner is made the same as the filesystem user ID of the
-creating process.
-The group of the file depends on a range of factors,
-including the type of filesystem,
-the options used to mount the filesystem,
-and whether or not the set-group-ID permission bit is enabled
-on the parent directory.
-If the filesystem supports the
-.I "\-o\ grpid"
-(or, synonymously
-.IR "\-o\ bsdgroups" )
-and
-.I "\-o\ nogrpid"
-(or, synonymously
-.IR "\-o\ sysvgroups" )
-.BR mount (8)
-options, then the rules are as follows:
-.IP * 2
-If the filesystem is mounted with
-.IR "\-o\ grpid" ,
-then the group of a new file is made
-the same as that of the parent directory.
-.IP *
-If the filesystem is mounted with
-.IR "\-o\ nogrpid"
-and the set-group-ID bit is disabled on the parent directory,
-then the group of a new file is made the same as the
-process's filesystem GID.
-.IP *
-If the filesystem is mounted with
-.IR "\-o\ nogrpid"
-and the set-group-ID bit is enabled on the parent directory,
-then the group of a new file is made
-the same as that of the parent directory.
-.PP
-As at Linux 2.6.25,
-the
-.IR "\-o\ grpid"
-and
-.IR "\-o\ nogrpid"
-mount options are supported by ext2, ext3, ext4, and XFS.
-Filesystems that don't support these mount options follow the
-.IR "\-o\ nogrpid"
-rules.
-.SS Glibc notes
-On older kernels where
-.BR fchownat ()
-is unavailable, the glibc wrapper function falls back to the use of
-.BR chown ()
-and
-.BR lchown ().
-When
-.I pathname
-is a relative pathname,
-glibc constructs a pathname based on the symbolic link in
-.IR /proc/self/fd
-that corresponds to the
-.IR dirfd
-argument.
-.SS NFS
-The
-.BR chown ()
-semantics are deliberately violated on NFS filesystems
-which have UID mapping enabled.
-Additionally, the semantics of all system
-calls which access the file contents are violated, because
-.BR chown ()
-may cause immediate access revocation on already open files.
-Client side
-caching may lead to a delay between the time where ownership have
-been changed to allow access for a user and the time where the file can
-actually be accessed by the user on other clients.
-.SS Historical details
-The original Linux
-.BR chown (),
-.BR fchown (),
-and
-.BR lchown ()
-system calls supported only 16-bit user and group IDs.
-Subsequently, Linux 2.4 added
-.BR chown32 (),
-.BR fchown32 (),
-and
-.BR lchown32 (),
-supporting 32-bit IDs.
-The glibc
-.BR chown (),
-.BR fchown (),
-and
-.BR lchown ()
-wrapper functions transparently deal with the variations across kernel versions.
-
-In versions of Linux prior to 2.1.81 (and distinct from 2.1.46),
-.BR chown ()
-did not follow symbolic links.
-Since Linux 2.1.81,
-.BR chown ()
-does follow symbolic links, and there is a new system call
-.BR lchown ()
-that does not follow symbolic links.
-Since Linux 2.1.86, this new call (that has the same semantics
-as the old
-.BR chown ())
-has got the same syscall number, and
-.BR chown ()
-got the newly introduced number.
-.SH EXAMPLE
-.PP
-The following program changes the ownership of the file named in
-its second command-line argument to the value specified in its
-first command-line argument.
-The new owner can be specified either as a numeric user ID,
-or as a username (which is converted to a user ID by using
-.BR getpwnam (3)
-to perform a lookup in the system password file).
-.SS Program source
-.nf
-#include <pwd.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-
-int
-main(int argc, char *argv[])
-{
- uid_t uid;
- struct passwd *pwd;
- char *endptr;
-
- if (argc != 3 || argv[1][0] == \(aq\\0\(aq) {
- fprintf(stderr, "%s <owner> <file>\\n", argv[0]);
- exit(EXIT_FAILURE);
- }
-
- uid = strtol(argv[1], &endptr, 10); /* Allow a numeric string */
-
- if (*endptr != \(aq\\0\(aq) { /* Was not pure numeric string */
- pwd = getpwnam(argv[1]); /* Try getting UID for username */
- if (pwd == NULL) {
- perror("getpwnam");
- exit(EXIT_FAILURE);
- }
-
- uid = pwd\->pw_uid;
- }
-
- if (chown(argv[2], uid, \-1) == \-1) {
- perror("chown");
- exit(EXIT_FAILURE);
- }
-
- exit(EXIT_SUCCESS);
-}
-.fi
-.SH SEE ALSO
-.BR chmod (2),
-.BR flock (2),
-.BR path_resolution (7),
-.BR symlink (7)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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