From Linux Man Pages
chown, fchown, lchown - change ownership of a file
SYNOPSIS
#include <sys/types.h>
#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);
DESCRIPTION
These system calls change the owner and group of the file specified by path or by fd. 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
behaviour depends on the kernel version. In case of a non-group-executable file (with clear S_IXGRP bit) 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(2).)
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.
NOTES
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.
The prototype for fchown() is only available if _BSD_SOURCE is defined.
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).
RESTRICTIONS
The chown() semantics are deliberately violated on NFS file systems which have UID mapping enabled. Addition-
ally, 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.
RELATED
chmod(2), fchownat(2), flock(2), path_resolution(2)
CATEGORY