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ARCHIVE_WRITE_DISK(3)  FreeBSD Library Functions Manual	 ARCHIVE_WRITE_DISK(3)

NAME
     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_standard_lookup,
     archive_write_disk_set_user_lookup, archive_write_header,
     archive_write_data, archive_write_data_block, archive_write_finish_entry,
     archive_write_close, archive_write_finish archive_write_free -- functions
     for creating objects on disk

LIBRARY
     Streaming Archive Library (libarchive, -larchive)

SYNOPSIS
     #include <archive.h>

     struct archive *
     archive_write_disk_new(void);

     int
     archive_write_disk_set_options(struct archive *, int flags);

     int
     archive_write_disk_set_skip_file(struct archive *,	dev_t, ino_t);

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

     int
     archive_write_disk_set_standard_lookup(struct archive *);

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

     int
     archive_write_header(struct archive *, struct archive_entry *);

     ssize_t
     archive_write_data(struct archive *, const	void *,	size_t);

     ssize_t
     archive_write_data_block(struct archive *,	const void *, size_t size,
	 int64_t offset);

     int
     archive_write_finish_entry(struct archive *);

     int
     archive_write_close(struct	archive	*);

     int
     archive_write_finish(struct archive *);

     int
     archive_write_free(struct archive *);

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

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

     archive_write_disk_set_skip_file()
	     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
	     being read.  This capability is technically unnecessary but can
	     be	a significant performance optimization in practice.

     archive_write_disk_set_options()
	     The options field consists	of a bitwise OR	of one or more of the
	     following values:
	     ARCHIVE_EXTRACT_OWNER
		     The user and group	IDs should be set on the restored
		     file.  By default,	the user and group IDs are not
		     restored.
	     ARCHIVE_EXTRACT_PERM
		     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.
	     ARCHIVE_EXTRACT_TIME
		     The timestamps (mtime, ctime, and atime) should be
		     restored.	By default, they are ignored.  Note that
		     restoring of atime	is not currently supported.
	     ARCHIVE_EXTRACT_NO_OVERWRITE
		     Existing files on disk will not be	overwritten.  By
		     default, existing regular files are truncated and over-
		     written; existing directories will	have their permissions
		     updated; other pre-existing objects are unlinked and
		     recreated from scratch.
	     ARCHIVE_EXTRACT_UNLINK
		     Existing files on disk will be unlinked before any
		     attempt 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.
	     ARCHIVE_EXTRACT_ACL
		     Attempt to	restore	ACLs.  By default, extended ACLs are
		     ignored.
	     ARCHIVE_EXTRACT_FFLAGS
		     Attempt to	restore	extended file flags.  By default, file
		     flags are ignored.
	     ARCHIVE_EXTRACT_XATTR
		     Attempt to	restore	POSIX.1e extended attributes.  By
		     default, they are ignored.
	     ARCHIVE_EXTRACT_SECURE_SYMLINKS
		     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 ARCHIVE_EXTRACT_UNLINK is speci-
		     fied 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.
	     ARCHIVE_EXTRACT_SECURE_NODOTDOT
		     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
		     error, regardless of this flag.
	     ARCHIVE_EXTRACT_SPARSE
		     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_write_disk_set_group_lookup(),
	     archive_write_disk_set_user_lookup()
	     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.

     archive_write_disk_set_standard_lookup()
	     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
	     getgrnam(3).

     archive_write_header()
	     Build and write a header using the	data in	the provided struct
	     archive_entry structure.  See archive_entry(3) for	information on
	     creating and populating struct archive_entry objects.

     archive_write_data()
	     Write data	corresponding to the header just written.  Returns
	     number of bytes written or	-1 on error.

     archive_write_data_block()
	     Write data	corresponding to the header just written.  This	is
	     like archive_write_data() except that it performs a seek on the
	     file being	written	to the specified offset	before writing the
	     data.  This is useful when	restoring sparse files from archive
	     formats that support sparse files.	 Returns number	of bytes writ-
	     ten or -1 on error.  (Note: This is currently not supported for
	     archive_write handles, only for archive_write_disk	handles.)

     archive_write_finish_entry()
	     Close out the entry just written.	Ordinarily, clients never need
	     to	call this, as it is called automatically by
	     archive_write_next_header() and archive_write_close() as needed.
	     However, some file	attributes are written to disk only after the
	     file is closed, so	this can be necessary if you need to work with
	     the file on disk right away.

     archive_write_close()
	     Set any attributes	that could not be set during the initial
	     restore.  For example, directory timestamps are not restored ini-
	     tially because restoring a	subsequent file	would alter that time-
	     stamp.  Similarly,	non-writable directories are initially created
	     with write	permissions (so	that their contents can	be restored).
	     The archive_write_disk_new	library	maintains a list of all	such
	     deferred attributes and sets them when this function is invoked.

     archive_write_finish()
	     This is a deprecated synonym for archive_write_free().

     archive_write_free()
	     Invokes archive_write_close() if it was not invoked manually,
	     then releases all resources.
     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).

RETURN VALUES
     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-
     ble.

     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.

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

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

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

AUTHORS
     The libarchive library was	written	by Tim Kientzle	<kientzle@acm.org>.

BUGS
     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.
     Explicit objects are created obeying the current umask unless
     ARCHIVE_EXTRACT_PERM is specified,	in which case they current umask is
     ignored.

     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
     particular	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.

FreeBSD	9.3		       February	2, 2012			   FreeBSD 9.3

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY | AUTHORS | BUGS

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