chown(2)
Name
chown, fchown − change owner and group of a file
Syntax
#include <sys/types.h>
chown(path, owner, group)
char *path;
uid_t owner;
gid_t group;
fchown(fd, owner, group)
int fd;
uid_t owner;
gid_t group;
Description
The chown and fchown system calls change the owner and group of the file named by path or referenced by fd . Only the superuser can change the owner of a file. Other users can change the group-id of a file that they own to another group to which they belong.
If you specify −1 in owner or group, the corresponding owner-id or group-id of the file is unchanged.
The chown system call clears the set-user-id and set-group-id bits on the file when it returns successfully, unless the call is made by the superuser. Clearing these bits when a file’s owner is changed protects the file from remaining set-user-id or set-group-id after being modified. If a file, specifically a program, remained set-user-id or set-group-id after being modified, that file could allow unauthorized access to other files or accounts.
You should use the fchown system call with the file locking primitives because fchown preserves any locks you previously obtained with the flock system call. For more information about file locking, see the flock() reference page.
Return Values
The chown and fchown calls return zero if the operation is successful; if an error occurs they return −1 and store a more specific error code in the global variable errno.
Environment
System Five
Differs from the System V definition in that only the superuser can change the ownership of a file. In addition, ELOOP is a possible error condition.
POSIX
When your program is compiled in the POSIX environment, the owner argument is of type uid_t, and the group argument is of type gid_t.
Diagnostics
The chown system call fails and the file is unchanged under the following conditions:
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG]
A component of a pathname exceeded 255 characters, or an entire pathname exceeded 1023 characters.
[ENOENT] The named file does not exist.
[EACCES] Search permission is denied for a component of the path prefix.
[EPERM] The effective user-id is not the superuser.
[EROFS] The named file resides on a read-only file system.
[EFAULT] The pathname points outside the process’s allocated address space.
[ELOOP] Too many symbolic links are encountered in translating the pathname.
[EIO] An I/O error occurs while reading from or writing to the file system.
[ESTALE] The fd argument is invalid because the file referred to by that file handle no longer exists or has been revoked.
The fchown system call fails if:
[EBADF] The fd argument does not refer to a valid descriptor.
[EINVAL] The fd argument refers to a socket, not a file.
[EPERM] The effective user-id is not the superuser.
[EROFS] The named file resides on a read-only file system.
[EIO] An I/O error occurred while reading from or writing to the file system.
[ETIMEDOUT] A connect request or remote file operation fails because the connected party does not properly respond after a period of time that is dependent on the communications protocol.