fchown

CHOWN(2)                     BSD System Calls Manual                    CHOWN(2)

NAME
     chown, fchown, lchown, fchownat — change owner and group of a file

LIBRARY
     Standard C Library (libc, -lc)

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);

     int
     fchownat(int fd, const char *path, uid_t owner, gid_t group, int flag);

DESCRIPTION
     The owner ID and group ID of the file named by path or referenced by fd is
     changed as specified by the arguments owner and group.  The owner of a file
     may change the group to a group of which he or she is a member, but the
     change owner capability is restricted to the super-user.

     The chown() system call clears the set-user-id and set-group-id bits on the
     file to prevent accidental or mischievous creation of set-user-id and set-
     group-id programs if not executed by the super-user.  The chown() system
     call follows symbolic links to operate on the target of the link rather
     than the link itself.

     The fchown() system call is particularly useful when used in conjunction
     with the file locking primitives (see flock(2)).

     The lchown() system call is similar to chown() but does not follow symbolic
     links.

     The fchownat() system call is equivalent to the chown() and lchown() except
     in the case where path specifies a relative path.  In this case the file to
     be changed is determined relative to the directory associated with the file
     descriptor fd instead of the current working directory.

     Values for flag are constructed by a bitwise-inclusive OR of flags from the
     following list, defined in <fcntl.h>:

     AT_SYMLINK_NOFOLLOW
             If path names a symbolic link, ownership of the symbolic link is
             changed.

     If fchownat() is passed the special value AT_FDCWD in the fd parameter, the
     current working directory is used and the behavior is identical to a call
     to chown() or lchown() respectively, depending on whether or not the
     AT_SYMLINK_NOFOLLOW bit is set in the flag argument.

     One of the owner or group id's may be left unchanged by specifying it as
     -1.

RETURN VALUES
     Upon successful completion, the value 0 is returned; otherwise the value -1
     is returned and the global variable errno is set to indicate the error.

ERRORS
     The chown() and lchown() will fail and the file will be unchanged if:

     [ENOTDIR]          A component of the path prefix is not a directory.

     [ENAMETOOLONG]     A component of a pathname exceeded 255 characters, or an
                        entire path name exceeded 1023 characters.

     [ENOENT]           The named file does not exist.

     [EACCES]           Search permission is denied for a component of the path
                        prefix.

     [ELOOP]            Too many symbolic links were encountered in translating
                        the pathname.

     [EPERM]            The operation would change the ownership, but the
                        effective user ID is not the super-user.

     [EPERM]            The named file has its immutable or append-only flag
                        set, see the chflags(2) manual page for more
                        information.

     [EROFS]            The named file resides on a read-only file system.

     [EFAULT]           The path argument points outside the process's allocated
                        address space.

     [EIO]              An I/O error occurred while reading from or writing to
                        the file system.

     The fchown() system call will fail 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 super-user.

     [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.

     In addition to the errors specified for chown() and lchown(), the
     fchownat() system call may fail if:

     [EBADF]            The path argument does not specify an absolute path and
                        the fd argument is neither AT_FDCWD nor a valid file
                        descriptor open for searching.

     [EINVAL]           The value of the flag argument is not valid.

     [ENOTDIR]          The path argument is not an absolute path and fd is
                        neither AT_FDCWD nor a file descriptor associated with a
                        directory.

SEE ALSO
     chgrp(1), chflags(2), chmod(2), flock(2), chown(8)

STANDARDS
     The chown() system call is expected to conform to ISO/IEC 9945-1:1990
     (“POSIX.1”).  The fchownat() system call follows The Open Group Extended
     API Set 2 specification.

HISTORY
     The chown() function appeared in Version 1 AT&T UNIX.  The fchown() system
     call appeared in 4.2BSD.

     The chown() system call was changed to follow symbolic links in 4.4BSD.
     The lchown() system call was added in FreeBSD 3.0 to compensate for the
     loss of functionality.

     The fchownat() system call appeared in FreeBSD 8.0.

BSD                             December 1, 2017                             BSD