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System Calls                                             chmod(2)



NAME
     chmod, fchmod - change access permission mode of file

SYNOPSIS
     #include <sys/types.h>
     #include <sys/stat.h>

     int chmod(const char *path, mode_t mode);

     int fchmod(int fildes, mode_t mode);

DESCRIPTION
     The chmod() and fchmod() functions set the access permission
     portion  of the mode of the file whose name is given by path
     or referenced by the open file descriptor fildes to the  bit
     pattern contained in mode. Access permission bits are inter-
     preted as follows:

     S_ISUID      04000     Set user ID on execution.
     S_ISGID      020#0     Set group ID on execution if #  is  7,
                            5,   3,   or   1.   Enable   mandatory
                            file/record locking if # is 6,  4,  2,
                            or 0.
     S_ISVTX      01000     Save text image  after execution.
     S_IRWXU      00700     Read, write, execute by owner.
     S_IRUSR      00400     Read by owner.
     S_IWUSR      00200     Write by owner.
     S_IXUSR      00100     Execute (search  if  a  directory)  by
                            owner.
     S_IRWXG      00070     Read, write, execute by group.
     S_IRGRP      00040     Read by group.
     S_IWGRP      00020     Write by group.
     S_IXGRP      00010     Execute by group.
     S_IRWXO      00007     Read, write, execute (search) by  oth-
                            ers.
     S_IROTH      00004     Read by others.
     S_IWOTH      00002     Write by others.
     S_IXOTH      00001     Execute by others.


     Modes are constructed by the bitwise  OR  operation  of  the
     access permission bits.

     The effective user ID of the process must match the owner of
     the  file or the process must have the appropriate privilege
     to change the mode of a file.

     If the process is not a privileged process and the  file  is
     not  a  directory, mode bit 01000 (save text image on execu-
     tion) is cleared.





SunOS 5.9           Last change: 28 Dec 1996                    1






System Calls                                             chmod(2)



     If neither the process is privileged, nor the  file's  group
     is  a member of the process's  supplementary group list, and
     the effective group ID of the process  does  not  match  the
     group ID of the file, mode bit 02000 (set group ID on execu-
     tion) is cleared.

     If a directory is writable and has S_ISVTX (the sticky  bit)
     set,  files  within that directory can be removed or renamed
     only if one or more of the following is true (see  unlink(2)
     and rename(2)):

        o  the user owns the file

        o  the user owns the directory

        o  the file is writable by the user

        o  the user is a privileged user

     If a directory has the set group ID bit set,  a  given  file
     created  within  that directory will have  the same group ID
     as the directory, if that group ID is part of the  group  ID
     set  of  the  process that created the file.  Otherwise, the
     newly created file's group ID will be set to  the  effective
     group ID of the creating process.

     If the mode bit 02000 (set group ID on execution) is set and
     the  mode bit 00010 (execute or search by group) is not set,
     mandatory file/record locking will exist on a regular  file.
     This  may affect future calls to open(2), creat(2), read(2),
     and write(2) on this file.

     Upon successful completion, chmod() and  fchmod()  mark  for
     update the st_ctime field of the file.

RETURN VALUES
     Upon successful completion, 0 is returned. Otherwise, -1  is
     returned,  the  file  mode is unchanged, and errno is set to
     indicate the error.

ERRORS
     The chmod() function will fail if:

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

     EFAULT
           The path argument points to an illegal address.

     EINTR A signal was caught during execution of the function.




SunOS 5.9           Last change: 28 Dec 1996                    2






System Calls                                             chmod(2)



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

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

     ENAMETOOLONG
           The length of the path argument exceeds  PATH_MAX,  or
           the  length of a path component exceeds NAME_MAX while
           _POSIX_NO_TRUNC is in effect.

     ENOENT
           Either a component of the  path  prefix  or  the  file
           referred  to by path does not exist or is a null path-
           name.

     ENOLINK
           The fildes argument points to a remote machine and the
           link to that machine is no longer active.

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

     EPERM The effective user ID does not match the owner of  the
           file and is not super-user.

     EROFS The file referred to by path resides  on  a  read-only
           file system.

     The fchmod() function will fail if:

     EBADF The fildes argument is not an open file descriptor

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

     EINTR A signal was caught during execution of  the  fchmod()
           function.

     ENOLINK
           The path argument points to a remote machine  and  the
           link to that machine is no longer active.

     EPERM The effective user ID does not match the owner of  the
           file   and  the  process  does  not  have  appropriate
           privilege.

     EROFS The file referred to by fildes resides on a  read-only
           file system.

ATTRIBUTES




SunOS 5.9           Last change: 28 Dec 1996                    3






System Calls                                             chmod(2)



     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | chmod() is Async-Signal-Safe|
    |_____________________________|_____________________________|


SEE ALSO
     chmod(1), chown(2), creat(2), fcntl(2),  mknod(2),  open(2),
     read(2),  rename(2),  stat(2),  write(2), mkfifo(3C), attri-
     butes(5), stat(3HEAD)

     Programming Interfaces Guide

NOTES
     If you use chmod() to change the file  group  owner  permis-
     sions  on a file with ACL entries, both the file group owner
     permissions and the ACL mask are changed to the new  permis-
     sions.   Be  aware  that  the  new ACL mask permissions  may
     change the effective permissions for  additional  users  and
     groups who  have ACL entries on the file.































SunOS 5.9           Last change: 28 Dec 1996                    4