chown(2) - NetBSD Manual Pages

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CHOWN(2)                  NetBSD Programmer's Manual                  CHOWN(2)


NAME

     chown, lchown, fchown - change owner and group of a file


SYNOPSIS

     #include <sys/types.h>
     #include <unistd.h>

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

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

     int
     fchown(int fd, uid_t owner, gid_t group);


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.

     When a called to change the owner of a file, chown(), lchown() and
     fchown() clear the set-user-id (S_ISUID) bit on the file.  When a called
     to change the group of a file, chown(), lchown() and fchown() clear the
     set-group-id (S_ISGID) bit on the file.  These actions are taken to pre-
     vent accidental or mischievous creation of set-user-id and set-group-id
     programs.

     lchown() is like chown() except in the case where the named file is a
     symbolic link, in which case lchown() changes the owner and group of the
     link, while chown() changes the owner and group of the file the link ref-
     erences.

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

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


RETURN VALUES

     Zero is returned if the operation was successful; -1 is returned if an
     error occurs, with a more specific error code being placed in the global
     variable errno.


ERRORS

     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 {NAME_MAX} characters,
                   or an entire path name exceeded {PATH_MAX} 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 effective user ID is not the super-user.

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

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

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

     fchown() will fail if:

     [EBADF]       fd does not refer to a valid descriptor.

     [EINVAL]      fd 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.


SEE ALSO

     chgrp(1), chmod(2), flock(2), chown(8)


STANDARDS

     The chown() function deviates from the semantics defined in IEEE
     Std1003.1-1990 (``POSIX''), which specifies that, unless the caller is
     the super-user, both the set-user-id and set-group-id bits on a file
     shall be cleared, regardless of the file attribute changed.  The lchown()
     and fchown() functions, as defined by X/Open Portability Guide Issue 4.2
     (``XPG4.2''), provide the same semantics.

     To retain conformance to these standards, compatibility interfaces are
     are provided by the POSIX Compatibility Library (libposix, -lposix) as
     follows:
     +   The chown() function conforms to IEEE Std1003.1-1990 (``POSIX'') and
         X/Open Portability Guide Issue 4.2 (``XPG4.2'').
     +   The lchown() and fchown() functions conform to X/Open Portability
         Guide Issue 4.2 (``XPG4.2'').


HISTORY

     The fchown() function call appeared in 4.2BSD.

     The chown() and fchown() functions were changed to follow symbolic links
     in 4.4BSD.  The lchown() function call appeared in NetBSD 1.3.

NetBSD 1.4                      April 19, 1994                               2