Provided by: manpages-dev_3.54-1ubuntu1_all bug


       chown, fchown, lchown - change ownership of a file


       #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);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       fchown(), lchown():
           || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L


       These system calls change the owner and group of a file.  They differ only in how the file
       is specified:

       * chown() changes the ownership of the file specified by path, which is dereferenced if it
         is a symbolic link.

       * fchown() changes the ownership of the file referred to by the open file descriptor fd.

       * lchown() is like chown(), but does not dereference symbolic links.

       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

       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  an  unprivileged  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  behavior  depends  on  the  kernel
       version.   In  case of a non-group-executable file (i.e., one for which the S_IXGRP bit is
       not set) the S_ISGID bit indicates mandatory 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 filesystem, 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

       EFAULT path points outside your accessible address space.

       ELOOP  Too many symbolic links were encountered in resolving path.

              path is too long.

       ENOENT The file does not exist.

       ENOMEM Insufficient kernel memory was available.

              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 filesystem.

       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.


       4.4BSD, SVr4, POSIX.1-2001.

       The  4.4BSD version can be used only by the superuser (that is, ordinary users cannot give
       away files).


       The original Linux chown(), fchown(), and lchown() system calls supported only 16-bit user
       and  group  IDs.   Subsequently,  Linux  2.4  added chown32(), fchown32(), and lchown32(),
       supporting 32-bit IDs.  The  glibc  chown(),  fchown(),  and  lchown()  wrapper  functions
       transparently deal with the variations across kernel versions.

       When  a  new file is created (by, for example, open(2) or mkdir(2)), its owner is made the
       same as the filesystem user ID of the creating process.  The group of the file depends  on
       a  range  of  factors,  including  the  type  of filesystem, the options used to mount the
       filesystem, and whether or not the set-group-ID permission bit is enabled  on  the  parent
       directory.   If  the  filesystem supports the -o grpid (or, synonymously -o bsdgroups) and
       -o nogrpid (or, synonymously -o sysvgroups)  mount(8)  options,  then  the  rules  are  as

       * If  the  filesystem  is  mounted with -o grpid, then the group of a new file is made the
         same as that of the parent directory.

       * If the filesystem is mounted with -o nogrpid and the set-group-ID bit is disabled on the
         parent  directory,  then  the  group  of  a  new  file is made the same as the process's
         filesystem GID.

       * If the filesystem is mounted with -o nogrpid and the set-group-ID bit is enabled on  the
         parent  directory,  then  the group of a new file is made the same as that of the parent

       As at Linux 2.6.25, the -o grpid and -o nogrpid mount options are supported by ext2, ext3,
       ext4,  and  XFS.  Filesystems that don't support these mount options follow the -o nogrpid

       The chown() semantics are deliberately violated on NFS filesystems 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.

       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  following  program changes the ownership of the file named in its second command-line
       argument to the value specified in its first command-line argument.  The new owner can  be
       specified  either  as a numeric user ID, or as a username (which is converted to a user ID
       by using getpwnam(3) to perform a lookup in the system password file).

       #include <pwd.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>

       main(int argc, char *argv[])
           uid_t uid;
           struct passwd *pwd;
           char *endptr;

           if (argc != 3 || argv[1][0] == '\0') {
               fprintf(stderr, "%s <owner> <file>\n", argv[0]);

           uid = strtol(argv[1], &endptr, 10);  /* Allow a numeric string */

           if (*endptr != '\0') {         /* Was not pure numeric string */
               pwd = getpwnam(argv[1]);   /* Try getting UID for username */
               if (pwd == NULL) {

               uid = pwd->pw_uid;

           if (chown(argv[2], uid, -1) == -1) {



       chmod(2), fchownat(2), flock(2), path_resolution(7), symlink(7)


       This page is part of release 3.54 of the Linux man-pages project.  A  description  of  the
       project,     and    information    about    reporting    bugs,    can    be    found    at