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     archive_write_disk_new, archive_write_disk_set_options,
     archive_write_disk_set_skip_file, archive_write_disk_set_group_lookup,
     archive_write_disk_set_user_lookup	-- functions for creating objects on

     Streaming Archive Library (libarchive, -larchive)

     #include <archive.h>

     struct archive *

     archive_write_disk_set_options(struct archive *, int flags);

     archive_write_disk_set_skip_file(struct archive *,	dev_t, ino_t);

     archive_write_disk_set_group_lookup(struct	archive	*, void	*,
	 gid_t (*)(void	*, const char *gname, gid_t gid),
	 void (*cleanup)(void *));

     archive_write_disk_set_standard_lookup(struct archive *);

     archive_write_disk_set_user_lookup(struct archive *, void *,
	 uid_t (*)(void	*, const char *uname, uid_t uid),
	 void (*cleanup)(void *));

     These functions provide a complete	API for	creating objects on disk from
     struct archive_entry descriptions.	 They are most naturally used when ex-
     tracting objects from an archive using the	archive_read() interface.  The
     general process is	to read	struct archive_entry objects from an archive,
     then write	those objects to a struct archive object created using the
     archive_write_disk() family functions.  This interface is deliberately
     very similar to the archive_write() interface used	to write objects to a
     streaming archive.

	     Allocates and initializes a struct	archive	object suitable	for
	     writing objects to	disk.

	     Records the device	and inode numbers of a file that should	not be
	     overwritten.  This	is typically used to ensure that an extraction
	     process does not overwrite	the archive from which objects are be-
	     ing read.	This capability	is technically unnecessary but can be
	     a significant performance optimization in practice.

	     The options field consists	of a bitwise OR	of one or more of the
	     following values:
		     Attempt to	restore	Access Control Lists.  By default, ex-
		     tended ACLs are ignored.
		     Before removing a file system object prior	to replacing
		     it, clear platform-specific file flags which might	pre-
		     vent its removal.
		     Attempt to	restore	file attributes	(file flags).  By de-
		     fault, file attributes are	ignored.  See chattr(1)
		     (Linux) or	chflags(1) (FreeBSD, Mac OS X) for more	infor-
		     mation on file attributes.
		     Mac OS X specific.	 Restore metadata using	copyfile(3).
		     By	default, copyfile(3) metadata is ignored.
		     Existing files on disk will not be	overwritten.  By de-
		     fault, existing regular files are truncated and overwrit-
		     ten; existing directories will have their permissions up-
		     dated; other pre-existing objects are unlinked and	recre-
		     ated from scratch.
		     The user and group	IDs should be set on the restored
		     file.  By default,	the user and group IDs are not re-
		     Full permissions (including SGID, SUID, and sticky	bits)
		     should be restored	exactly	as specified, without obeying
		     the current umask.	 Note that SUID	and SGID bits can only
		     be	restored if the	user and group ID of the object	on
		     disk are correct.	If ARCHIVE_EXTRACT_OWNER is not	speci-
		     fied, then	SUID and SGID bits will	only be	restored if
		     the default user and group	IDs of newly-created objects
		     on	disk happen to match those specified in	the archive
		     entry.  By	default, only basic permissions	are restored,
		     and umask is obeyed.
		     Extract files atomically, by first	creating a unique tem-
		     porary file and then renaming it to its required destina-
		     tion name.	 This avoids a race where an application might
		     see a partial file	(or no file) during extraction.
		     Refuse to extract an absolute path.  The default is to
		     not refuse	such paths.
		     Refuse to extract a path that contains a .. element any-
		     where within it.  The default is to not refuse such
		     paths.  Note that paths ending in .. always cause an er-
		     ror, regardless of	this flag.
		     Refuse to extract any object whose	final location would
		     be	altered	by a symlink on	disk.  This is intended	to
		     help guard	against	a variety of mischief caused by	ar-
		     chives that (deliberately or otherwise) extract files
		     outside of	the current directory.	The default is not to
		     perform this check.  If
		     Scan data for blocks of NUL bytes and try to recreate
		     them with holes.  This results in sparse files, indepen-
		     dent of whether the archive format	supports or uses them.
		     ARCHIVE_EXTRACT_UNLINK is specified together with this
		     option, the library will remove any intermediate symlinks
		     it	finds and return an error only if such symlink could
		     not be removed.
		     The timestamps (mtime, ctime, and atime) should be	re-
		     stored.  By default, they are ignored.  Note that restor-
		     ing of atime is not currently supported.
		     Existing files on disk will be unlinked before any	at-
		     tempt to create them.  In some cases, this	can prove to
		     be	a significant performance improvement.	By default,
		     existing files are	truncated and rewritten, but the file
		     is	not recreated.	In particular, the default behavior
		     does not break existing hard links.
		     Attempt to	restore	extended file attributes.  By default,
		     they are ignored.	See xattr(7) (Linux), xattr(2) (Mac OS
		     X), or getextattr(8) (FreeBSD) for	more information on
		     extended file attributes.

	     The struct	archive_entry objects contain both names and ids that
	     can be used to identify users and groups.	These names and	ids
	     describe the ownership of the file	itself and also	appear in ACL
	     lists.  By	default, the library uses the ids and ignores the
	     names, but	this can be overridden by registering user and group
	     lookup functions.	To register, you must provide a	lookup func-
	     tion which	accepts	both a name and	id and returns a suitable id.
	     You may also provide a void * pointer to a	private	data structure
	     and a cleanup function for	that data.  The	cleanup	function will
	     be	invoked	when the struct	archive	object is destroyed.

	     This convenience function installs	a standard set of user and
	     group lookup functions.  These functions use getpwnam(3) and
	     getgrnam(3) to convert names to ids, defaulting to	the ids	if the
	     names cannot be looked up.	 These functions also implement	a sim-
	     ple memory	cache to reduce	the number of calls to getpwnam(3) and
     More information about the	struct archive object and the overall design
     of	the library can	be found in the	libarchive(3) overview.	 Many of these
     functions are also	documented under archive_write(3).

     Most functions return ARCHIVE_OK (zero) on	success, or one	of several
     non-zero error codes for errors.  Specific	error codes include:
     ARCHIVE_RETRY for operations that might succeed if	retried, ARCHIVE_WARN
     for unusual conditions that do not	prevent	further	operations, and
     ARCHIVE_FATAL for serious errors that make	remaining operations impossi-

     archive_write_disk_new() returns a	pointer	to a newly-allocated struct
     archive object.

     archive_write_data() returns a count of the number	of bytes actually
     written, or -1 on error.

     Detailed error codes and textual descriptions are available from the
     archive_errno() and archive_error_string()	functions.

     tar(1), archive_read(3), archive_write(3),	libarchive(3)

     The libarchive library first appeared in FreeBSD 5.3.  The
     archive_write_disk	interface was added to libarchive 2.0 and first	ap-
     peared in FreeBSD 6.3.

     The libarchive library was	written	by Tim Kientzle	<>.

     Directories are actually extracted	in two distinct	phases.	 Directories
     are created during	archive_write_header(),	but final permissions are not
     set until archive_write_close().  This separation is necessary to cor-
     rectly handle borderline cases such as a non-writable directory contain-
     ing files,	but can	cause unexpected results.  In particular, directory
     permissions are not fully restored	until the archive is closed.  If you
     use chdir(2) to change the	current	directory between calls	to
     archive_read_extract() or before calling archive_read_close(), you	may
     confuse the permission-setting logic with the result that directory per-
     missions are restored incorrectly.

     The library attempts to create objects with filenames longer than
     PATH_MAX by creating prefixes of the full path and	changing the current
     directory.	 Currently, this logic is limited in scope; the	fixup pass
     does not work correctly for such objects and the symlink security check
     option disables the support for very long pathnames.

     Restoring the path	aa/../bb does create each intermediate directory.  In
     particular, the directory aa is created as	well as	the final object bb.
     In	theory,	this can be exploited to create	an entire directory hierarchy
     with a single request.  Of	course,	this does not work if the
     ARCHIVE_EXTRACT_NODOTDOT option is	specified.

     Implicit directories are always created obeying the current umask.	 Ex-
     plicit objects are	created	obeying	the current umask unless
     ARCHIVE_EXTRACT_PERM is specified,	in which case they current umask is

     SGID and SUID bits	are restored only if the correct user and group	could
     be	set.  If ARCHIVE_EXTRACT_OWNER is not specified, then no attempt is
     made to set the ownership.	 In this case, SGID and	SUID bits are restored
     only if the user and group	of the final object happen to match those
     specified in the entry.

     The "standard" user-id and	group-id lookup	functions are not the defaults
     because getgrnam(3) and getpwnam(3) are sometimes too large for particu-
     lar applications.	The current design allows the application author to
     use a more	compact	implementation when appropriate.

     There should be a corresponding archive_read_disk interface that walks a
     directory hierarchy and returns archive entry objects.

BSD			       January 19, 2020				   BSD


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