mirror of https://github.com/mkerrisk/man-pages
185 lines
5.6 KiB
Groff
185 lines
5.6 KiB
Groff
.\" Hey Emacs! This file is -*- nroff -*- source.
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.\"
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.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
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.\" Copyright (c) 1998 Andries Brouwer (aeb@cwi.nl)
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" Modified by Michael Haardt <michael@moria.de>
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.\" Modified 1993-07-21 by Rik Faith <faith@cs.unc.edu>
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.\" Modified 1996-07-09 by Andries Brouwer <aeb@cwi.nl>
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.\" Modified 1996-11-06 by Eric S. Raymond <esr@thyrsus.com>
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.\" Modified 1997-05-18 by Michael Haardt <michael@cantor.informatik.rwth-aachen.de>
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.\" Modified 2004-06-23 by Michael Kerrisk <mtk-manpages@gmx.net>
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.\"
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.TH CHOWN 2 2004-06-23 "Linux 2.6.7" "Linux Programmer's Manual"
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.SH NAME
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chown, fchown, lchown \- change ownership of a file
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.SH SYNOPSIS
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.B #include <sys/types.h>
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.br
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.B #include <unistd.h>
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.sp
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.BI "int chown(const char *" path ", uid_t " owner ", gid_t " group );
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.br
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.BI "int fchown(int " fd ", uid_t " owner ", gid_t " group );
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.br
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.BI "int lchown(const char *" path ", uid_t " owner ", gid_t " group );
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.SH DESCRIPTION
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These system calls change the owner and group of the file specified by
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.I path
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or by
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.IR fd .
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Only a privileged process (Linux: one with the
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.B CAP_CHOWN
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capability) may change the owner of a file.
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The owner of a file may change the group of the file
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to any group of which that owner is a member.
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A privileged process (Linux: with
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.BR CAP_CHOWN )
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may change the group arbitrarily.
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If the
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.I owner
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or
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.I group
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is specified as \-1, then that ID is not changed.
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When the owner or group of an executable file are changed by a non-superuser,
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the S_ISUID and S_ISGID mode bits are cleared. POSIX does not specify whether
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this also should happen when root does the
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.BR chown ();
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the Linux behaviour depends on the kernel version.
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.\" In Linux 2.0 kernels, superuser was like everyone else
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.\" In 2.2, up to 2.2.12, these bits were not cleared for superuser.
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.\" Since 2.2.13, superuser is once more like everyone else.
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In case of a non-group-executable file (with clear S_IXGRP bit)
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the S_ISGID bit indicates mandatory locking, and is not cleared
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by a
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.BR chown ().
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.SH "RETURN VALUE"
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On success, zero is returned. On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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Depending on the file system, other errors can be returned. The more
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general errors for
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.BR chown ()
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are listed below.
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.TP
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.B EACCES
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Search permission is denied on a component of the path prefix.
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(See also
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.BR path_resolution (2).)
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.TP
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.B EFAULT
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.I path
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points outside your accessible address space.
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.TP
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.B ELOOP
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Too many symbolic links were encountered in resolving
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.IR path .
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.TP
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.B ENAMETOOLONG
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.I path
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is too long.
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.TP
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.B ENOENT
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The file does not exist.
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.TP
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.B ENOMEM
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Insufficient kernel memory was available.
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.TP
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.B ENOTDIR
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A component of the path prefix is not a directory.
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.TP
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.B EPERM
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The calling process did not have the required permissions
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(see above) to change owner and/or group.
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.TP
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.B EROFS
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The named file resides on a read-only file system.
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.PP
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The general errors for
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.BR fchown ()
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are listed below:
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.TP
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.B EBADF
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The descriptor is not valid.
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.TP
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.B EIO
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A low-level I/O error occurred while modifying the inode.
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.TP
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.B ENOENT
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See above.
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.TP
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.B EPERM
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See above.
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.TP
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.B EROFS
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See above.
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.SH NOTES
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In versions of Linux prior to 2.1.81 (and distinct from 2.1.46),
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.BR chown ()
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did not follow symbolic links.
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Since Linux 2.1.81,
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.BR chown ()
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does follow symbolic links, and there is a new system call
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.BR lchown ()
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that does not follow symbolic links.
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Since Linux 2.1.86, this new call (that has the same semantics
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as the old
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.BR chown ())
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has got the same syscall number, and
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.BR chown ()
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got the newly introduced number.
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.LP
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The prototype for
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.BR fchown ()
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is only available if
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.B _BSD_SOURCE
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is defined.
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.SH "CONFORMING TO"
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The
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.BR chown ()
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call conforms to SVr4, SVID, POSIX, X/OPEN. The 4.4BSD version can only be
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used by the superuser (that is, ordinary users cannot give away files).
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SVr4 documents EINVAL, EINTR, ENOLINK and EMULTIHOP returns, but no
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ENOMEM. POSIX.1 does not document ENOMEM or ELOOP error conditions.
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.PP
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The
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.BR fchown ()
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call conforms to 4.4BSD and SVr4.
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SVr4 documents additional EINVAL, EIO, EINTR, and ENOLINK error conditions.
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.SH RESTRICTIONS
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The \fBchown\fP() semantics are deliberately violated on NFS file systems
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which have UID mapping enabled. Additionally, the semantics of all system
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calls which access the file contents are violated, because \fBchown\fP()
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may cause immediate access revocation on already open files. Client side
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caching may lead to a delay between the time where ownership have
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been changed to allow access for a user and the time where the file can
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actually be accessed by the user on other clients.
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.SH "SEE ALSO"
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.BR chmod (2),
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.BR flock (2),
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.BR path_resolution (2)
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