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

NAME
     chmod, lchmod, fchmod -- change mode of file

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <sys/stat.h>

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

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

     int
     fchmod(int	fd, mode_t mode);

DESCRIPTION
     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.  lchmod() is	like chmod() except in the
     case where	the named file is a symbolic link, in which case lchmod() sets
     the permission bits of the	link, while chmod() sets the bits of the file
     the link references.  chmod() verifies that the process owner (user) ei-
     ther 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 <sys/stat.h>:
	   #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 */

     The mode ISVTX (the `sticky bit') can be set on a regular file by the su-
     per-user, but has no effect.

     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 information about	the history and	properties of the sticky bit,
     see sticky(7).

     Changing the owner	of a file turns	off the	set-user-id and	set-group-id
     bits; writing to a	file turns off the set-user-id and set-group-id	bits
     unless the	user is	the super-user.	 This makes the	system 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.

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

ERRORS
     chmod() and lchmod() 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 {NAME_MAX} charac-
			ters, or an entire path	name exceeded {PATH_MAX} char-
			acters.

     [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.

     [EPERM]		The mode includes the setgid bit (S_ISGID) but the
			file's group is	neither	the effective group ID nor is
			it in the group	access list.

     [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.

     [EFTYPE]		The effective user ID is not the super-user, the mode
			includes the sticky bit	(S_ISVTX), and path does not
			refer to a directory.

     fchmod() will fail	if:

     [EBADF]		The descriptor is not valid.

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

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

     [EPERM]		The mode includes the setgid bit (S_ISGID) but the
			file's group is	neither	the effective group ID nor is
			it in the group	access list.

     [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.

     [EFTYPE]		The effective user ID is not the super-user, the mode
			includes the sticky bit	(S_ISVTX), and fd does not re-
			fer to a directory.

SEE ALSO
     chmod(1), chflags(2), chown(2), open(2), stat(2), getmode(3), setmode(3),
     sticky(7),	symlink(7)

STANDARDS
     The chmod() function conforms to ISO/IEC 9945-1:1990 ("POSIX.1").

HISTORY
     The fchmod() function call	appeared in 4.2BSD.  The lchmod() function
     call appeared in NetBSD 1.3.

BSD			       October 11, 2011				   BSD

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY

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