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|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 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:|
|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_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.
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.
|ARCHIVE_WRITE_DISK (3)||February 28, 2017|
|Main index||Section 3||Options|