Provided by: libarchive-dev_3.1.2-7ubuntu2.8_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 *);

     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 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_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.