chown, fchown, lchown - change ownership of a file


     #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


     The owner of the file specified by path or by fd is changed.
     Only  the  super-user  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.  The super-user 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-super-user,  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 man-
     datory locking, and is not cleared by a chown.


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


     Depending on the file system, other errors can be  returned.
     The more general errors for chown are listed below:

     EPERM   The effective UID does not match the  owner  of  the
             file,  and  is  not zero; or the owner or group were
             specified incorrectly.

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

     EFAULT  path points outside your accessible address space.

             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.

     EACCES  Search permission is denied on a  component  of  the
             path prefix.

     ELOOP   Too many symbolic links were encountered in  resolv-
             ing path.

     The general errors for fchown are listed below:

     EBADF   The descriptor is not valid.

     ENOENT  See above.

     EPERM   See above.

     EROFS   See above.

     EIO     A low-level I/O error occurred while  modifying  the


     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  seman-
     tics  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  __USE_BSD  is


     The chown call conforms to SVr4, SVID, POSIX,  X/OPEN.   The
     4.4BSD  version  can only be used by the superuser (that is,
     ordinary users cannot give away files).  SVr4 documents EIN-
     VAL,  EINTR,  ENOLINK  and EMULTIHOP returns, but no ENOMEM.
     POSIX.1 does not document ENOMEM or ELOOP error conditions.

     The fchown call conforms to 4.4BSD and SVr4.  SVr4 documents
     additional EINVAL, EIO, EINTR, and ENOLINK error conditions.


     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.


     chmod(2), flock(2)