Provided by: libarchive-dev_3.2.2-3.1ubuntu0.7_amd64 bug

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 *);

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

     la_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 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.

     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 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 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 overwritten; 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 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.
             ARCHIVE_EXTRACT_SECURE_NODOTDOT
                     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.
             ARCHIVE_EXTRACT_SECURE_NOABSOLUTEPATHS
                     Refuse to extract an absolute path.  The default is to not refuse such paths.
             ARCHIVE_EXTRACT_SPARSE
                     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_EXTRACT_CLEAR_NOCHANGE_FFLAGS
                     Before removing a file system object prior to replacing it, clear platform-specific file
                     flags which might prevent its removal.

     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.

     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 simple 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 written 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 initially because restoring a subsequent file would alter that
             timestamp.  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 impossible.

     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 correctly handle borderline cases such as a non-writable directory containing 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 permissions 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.