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NetBSD 6.1.5 - man page for archive_write_disk_set_standard_lookup (netbsd section 3)

archive_write_disk(3)		   BSD Library Functions Manual 	    archive_write_disk(3)

     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_finish_entry, archive_write_close, archive_write_finish -- functions for cre-
     ating objects on disk

     #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 *));

     archive_write_header(struct archive *, struct archive_entry *);

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

     archive_write_finish_entry(struct archive *);

     archive_write_close(struct archive *);

     archive_write_finish(struct archive *);

     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 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

	     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 ar-
	     chive from which objects are being 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:
		     The user and group IDs should be set on the restored file.  By default, the
		     user and group IDs are not restored.
		     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 specified, 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
		     The timestamps (mtime, ctime, and atime) should be restored.  By default,
		     they are ignored.	Note that restoring of atime is not currently supported.
		     Existing files on disk will not be overwritten.  By default, existing regu-
		     lar files are truncated and overwritten; existing directories will have
		     their permissions updated; other pre-existing objects are unlinked and
		     recreated from scratch.
		     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
		     Attempt to restore ACLs.  By default, extended ACLs are ignored.
		     Attempt to restore extended file flags.  By default, file flags are ignored.
		     Attempt to restore POSIX.1e extended attributes.  By default, they are
		     Refuse to extract any object whose final location would be altered by a sym-
		     link on disk.  This is intended to help guard against a variety of mischief
		     caused by archives that (deliberately or otherwise) extract files outside of
		     the current directory.  The default is not to perform this check.	If
		     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.
		     Refuse to extract a path that contains a .. element anywhere within it.  The
		     default is to not refuse such paths.  Note that paths ending in .. always
		     cause an error, regardless of this flag.
		     Scan data for blocks of NUL bytes and try to recreate them with holes.  This
		     results in sparse files, independent 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 function 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 func-
	     tions.  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 imple-
	     ment a simple memory cache to reduce the number of calls to getpwnam(3) and

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

	     Write data corresponding to the header just written.  Returns number of bytes writ-
	     ten or -1 on error.

	     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.

	     Set any attributes that could not be set during the initial restore.  For example,
	     directory timestamps are not restored initially because restoring a subsequent file
	     would alter that timestamp.  Similarly, non-writable directories are initially cre-
	     ated 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.

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

     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 impossible.  The
     archive_errno() and archive_error_string() functions can be used to retrieve an appropriate
     error code and a textual error message.

     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.  On error, -1
     is returned and the archive_errno() and archive_error_string() functions will return appro-
     priate values.

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

     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.

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

     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 correctly handle borderline cases such as a non-writable direc-
     tory containing files, but can cause unexpected results.  In particular, directory permis-
     sions 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 permissions are restored incorrectly.

     The library attempts to create objects with filenames longer than PATH_MAX by creating pre-
     fixes 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 heirarchy 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 cur-
     rent design allows the application author to use a more compact implementation when appro-

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

BSD					  August 5, 2008				      BSD

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