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CHMOD(2)		    BSD	System Calls Manual		      CHMOD(2)

     chmod, fchmod -- change mode of file

     #include <sys/stat.h>

     chmod(const char *path, mode_t mode);

     fchmod(int	fd, mode_t mode);

     The function chmod() sets the file	permission bits	of the file specified
     by	the pathname path to mode.  Fchmod() sets the permission bits of the
     specified file descriptor fd.  Chmod() verifies that the process owner
     (user) either owns	the file specified by path (or fd), or is the super-
     user.  A mode is created from or'd	permission bit masks defined in

	   #define S_IRWXU 0000700    /* RWX mask for owner */
	   #define S_IRUSR 0000400    /* R for owner */
	   #define S_IWUSR 0000200    /* W for owner */
	   #define S_IXUSR 0000100    /* X for owner */

	   #define S_IRWXG 0000070    /* RWX mask for group */
	   #define S_IRGRP 0000040    /* R for group */
	   #define S_IWGRP 0000020    /* W for group */
	   #define S_IXGRP 0000010    /* X for group */

	   #define S_IRWXO 0000007    /* RWX mask for other */
	   #define S_IROTH 0000004    /* R for other */
	   #define S_IWOTH 0000002    /* W for other */
	   #define S_IXOTH 0000001    /* X for other */

	   #define S_ISUID 0004000    /* set user id on	execution */
	   #define S_ISGID 0002000    /* set group id on execution */
	   #define S_ISVTX 0001000    /* sticky	bit */
	   #ifndef _POSIX_SOURCE
	   #define S_ISTXT 0001000

     The FreeBSD VM system totally ignores the sticky bit (ISVTX ) for exe-
     cutables.	On UFS-based filesystems (FFS, MFS, LFS) the sticky bit	may
     only be set upon directories.

     If	mode ISVTX (the	`sticky	bit') is set on	a directory, an	unprivileged
     user may not delete or rename files of other users	in that	directory. The
     sticky bit	may be set by any user on a directory which the	user owns or
     has appropriate permissions.  For more details of the properties of the
     sticky bit, see sticky(8).

     If	mode ISUID (set	UID) is	set on a directory, and	the MNT_SUIDDIR	option
     was used in the mount of the filesystem, then the owner of	any new	files
     and sub-directories created within	this directory are set to be the same
     as	the owner of that directory.  If this function is enabled, new direc-
     tories will inherit the bit from their parents.  Execute bits are removed
     from the file, and	it will	not be given to	root. This behaviour does not
     change the	requirements for the user to be	allowed	to write the file, but
     only the eventual owner after it has been created.	Group inheritance is
     not effected.

     This feature is designed for use on fileservers serving PC	users via ftp,
     SAMBA, or netatalk. It provides security holes for	shell users and	as
     such should not be	used on	shell machines,	especially on home directo-
     ries.  This option	requires the SUIDDIR option in the kernel to work.
     Only UFS filesystems support this option.	For more details of the	suid-
     dir mount option, see mount(8).

     Writing or	changing the owner of a	file turns off the set-user-id and
     set-group-id bits unless the user is the super-user.  This	makes the sys-
     tem somewhat more secure by protecting set-user-id	(set-group-id) files
     from remaining set-user-id	(set-group-id) if they are modified, at	the
     expense of	a degree of compatibility.

     Upon successful completion, a value of 0 is returned.  Otherwise, a value
     of	-1 is returned and errno is set	to indicate the	error.

     Chmod() will fail and the file mode 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 translat-
			ing the	pathname.

     [EPERM]		The effective user ID does not match the owner of the
			file and 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

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

     [EFTYPE]		An attempt was made to set the sticky bit upon an exe-

     Fchmod() will fail	if:

     [EBADF]		The descriptor is not valid.

     [EINVAL]		refers to a socket, not	to a file.

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

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

     chmod(1), chown(2), open(2), stat(2), sticky(8)

     The chmod() function call is expected to conform to ISO/IEC 9945-1:1990
     ("POSIX.1"), except for the return	of EFTYPE and the use of S_ISTXT.

     A chmod() function	call appeared in Version 7 AT&T	UNIX.  The fchmod()
     function call appeared in 4.2BSD.

4th Berkeley Distribution	 June 4, 1993	     4th Berkeley Distribution


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