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chown

chown

change file owner and group

  1. chown.1.man
  2. chown.2.man

1. chown.1.man

Manpage of CHOWN

CHOWN

Section: User Commands (1)
Updated: January 2010
Index Return to Main Contents
 

NAME

chown - change file owner and group  

SYNOPSIS

chown [OPTION]... [OWNER][:[GROUP]] FILE...
chown [OPTION]... --reference=RFILE FILE...  

DESCRIPTION

This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed.  

OPTIONS

Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE.

-c, --changes
like verbose but report only when a change is made
--dereference
affect the referent of each symbolic link (this is the default), rather than the symbolic link itself
-h, --no-dereference
affect each symbolic link instead of any referenced file (useful only on systems that can change the ownership of a symlink)
--from=CURRENT_OWNER:CURRENT_GROUP
change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute.
--no-preserve-root
do not treat `/' specially (the default)
--preserve-root
fail to operate recursively on `/'
-f, --silent, --quiet
suppress most error messages
--reference=RFILE
use RFILE's owner and group rather than specifying OWNER:GROUP values
-R, --recursive
operate on files and directories recursively
-v, --verbose
output a diagnostic for every file processed

The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect.

-H
if a command line argument is a symbolic link to a directory, traverse it
-L
traverse every symbolic link to a directory encountered
-P
do not traverse any symbolic links (default)
--help
display this help and exit
--version
output version information and exit

Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a `:' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic.  

EXAMPLES

chown root /u
Change the owner of /u to "root".
chown root:staff /u
Likewise, but also change its group to "staff".
chown -hR root /u
Change the owner of /u and subfiles to "root".
 

AUTHOR

Written by David MacKenzie and Jim Meyering.  

REPORTING BUGS

Report chown bugs to bug-coreutils@gnu.org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
Report chown translation bugs to <http://translationproject.org/team/>  

COPYRIGHT

Copyright © 2010 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.  

SEE ALSO

chown(2)

The full documentation for chown is maintained as a Texinfo manual. If the info and chown programs are properly installed at your site, the command

info coreutils aqchown invocationaq

should give you access to the complete manual.

 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
AUTHOR
REPORTING BUGS
COPYRIGHT
SEE ALSO
This document was created by man2html using the manual pages.
Time: 07:35:25 GMT, May 02, 2010

2. chown.2.man

Manpage of CHOWN

CHOWN

Section: Linux Programmer's Manual (2)
Updated: 2008-06-16
Index Return to Main Contents
 

NAME

chown, fchown, lchown - change ownership of a file  

SYNOPSIS

#include <unistd.h>

int chown(const char *path, uid_t owner, gid_t group);
int fchown(int fd, uid_t owner, gid_t group);
int lchown(const char *path, uid_t owner, gid_t group);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

fchown(), lchown(): _BSD_SOURCE || _XOPEN_SOURCE >= 500  

DESCRIPTION

These system calls change the owner and group of a file. The differ only in how the file is specified:
*
chown() changes the ownership of the file specified by path, which is dereferenced if it is a symbolic link.
*
fchown() changes the ownership of the file referred to by the open file descriptor fd.
*
lchown() is like chown(), but does not dereference symbolic links.

Only a privileged process (Linux: one with the 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 CAP_CHOWN) may change the group arbitrarily.

If the owner or group is specified as -1, then that ID is not changed.

When the owner or group of an executable file are changed by a non-superuser, the S_ISUID and S_ISGID mode bits are cleared. POSIX does not specify whether this also should happen when root does the chown(); the Linux behavior depends on the kernel version. In case of a non-group-executable file (i.e., one for which the S_IXGRP bit is not set) the S_ISGID bit indicates mandatory locking, and is not cleared by a chown().  

RETURN VALUE

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.  

ERRORS

Depending on the file system, other errors can be returned. The more general errors for chown() are listed below.
EACCES
Search permission is denied on a component of the path prefix. (See also path_resolution(7).)
EFAULT
path points outside your accessible address space.
ELOOP
Too many symbolic links were encountered in resolving path.
ENAMETOOLONG
path is too long.
ENOENT
The file does not exist.
ENOMEM
Insufficient kernel memory was available.
ENOTDIR
A component of the path prefix is not a directory.
EPERM
The calling process did not have the required permissions (see above) to change owner and/or group.
EROFS
The named file resides on a read-only file system.

The general errors for fchown() are listed below:

EBADF
The descriptor is not valid.
EIO
A low-level I/O error occurred while modifying the inode.
ENOENT
See above.
EPERM
See above.
EROFS
See above.
 

CONFORMING TO

4.4BSD, SVr4, POSIX.1-2001.

The 4.4BSD version can only be used by the superuser (that is, ordinary users cannot give away files).  

NOTES

When a new file is created (by, for example, open(2) or mkdir(2)), its owner is made the same as the file system user ID of the creating process. The group of the file depends on a range of factors, including the type of file system, the options used to mount the file system, and whether or not the set-group-ID permission bit is enabled on the parent directory. If the file system supports the -o grpid (or, synonymously -o bsdgroups) and -o nogrpid (or, synonymously -o sysvgroups) mount(8) options, then the rules are as follows:
*
If the file system is mounted with -o grpid, then the group of a new file is made the same as that of the parent directory.
*
If the file system is mounted with -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 file system GID.
*
If the file system is mounted with -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.

As at Linux 2.6.25, the -o grpid and -o nogrpid mount options are supported by ext2, ext3, ext4, and XFS. File systems that don't support these mount options follow the -o nogrpid rules.

The chown() semantics are deliberately violated on NFS file systems which have UID mapping enabled. Additionally, the semantics of all system calls which access the file contents are violated, because 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.

In versions of Linux prior to 2.1.81 (and distinct from 2.1.46), chown() did not follow symbolic links. Since Linux 2.1.81, chown() does follow symbolic links, and there is a new system call lchown() that does not follow symbolic links. Since Linux 2.1.86, this new call (that has the same semantics as the old chown()) has got the same syscall number, and chown() got the newly introduced number.  

EXAMPLE

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 getpwnam(3) to perform a lookup in the system password file). 


#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\0aq) {
        fprintf(stderr, "%s <owner> <file>
", argv[0]);
        exit(EXIT_FAILURE);
    }

    uid = strtol(argv[1], &endptr, 10);  /* Allow a numeric string */

    if (*endptr != aq\0aq) {         /* 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);
    } /* if */

    exit(EXIT_SUCCESS);
} /* main */
 

SEE ALSO

chmod(2), fchownat(2), flock(2), path_resolution(7), symlink(7)  

COLOPHON

This page is part of release 3.23 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
EXAMPLE
SEE ALSO
COLOPHON
This document was created by man2html using the manual pages.
Time: 07:35:25 GMT, May 02, 2010

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