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28 .Dt ARCHIVE_WRITE_DISK 3
31 .Nm archive_write_disk_new ,
32 .Nm archive_write_disk_set_options ,
33 .Nm archive_write_disk_set_skip_file ,
34 .Nm archive_write_disk_set_group_lookup ,
35 .Nm archive_write_disk_set_standard_lookup ,
36 .Nm archive_write_disk_set_user_lookup ,
37 .Nm archive_write_header ,
38 .Nm archive_write_data ,
39 .Nm archive_write_data_block ,
40 .Nm archive_write_finish_entry ,
41 .Nm archive_write_close ,
42 .Nm archive_write_finish
43 .Nm archive_write_free
44 .Nd functions for creating objects on disk
48 .Fn archive_write_disk_new "void"
50 .Fn archive_write_disk_set_options "struct archive *" "int flags"
52 .Fn archive_write_disk_set_skip_file "struct archive *" "dev_t" "ino_t"
54 .Fo archive_write_disk_set_group_lookup
55 .Fa "struct archive *"
57 .Fa "gid_t (*)(void *, const char *gname, gid_t gid)"
58 .Fa "void (*cleanup)(void *)"
61 .Fn archive_write_disk_set_standard_lookup "struct archive *"
63 .Fo archive_write_disk_set_user_lookup
64 .Fa "struct archive *"
66 .Fa "uid_t (*)(void *, const char *uname, uid_t uid)"
67 .Fa "void (*cleanup)(void *)"
70 .Fn archive_write_header "struct archive *" "struct archive_entry *"
72 .Fn archive_write_data "struct archive *" "const void *" "size_t"
74 .Fn archive_write_data_block "struct archive *" "const void *" "size_t size" "int64_t offset"
76 .Fn archive_write_finish_entry "struct archive *"
78 .Fn archive_write_close "struct archive *"
80 .Fn archive_write_finish "struct archive *"
82 .Fn archive_write_free "struct archive *"
84 These functions provide a complete API for creating objects on
86 .Tn struct archive_entry
88 They are most naturally used when extracting objects from an archive
92 The general process is to read
93 .Tn struct archive_entry
94 objects from an archive, then write those objects to a
96 object created using the
97 .Fn archive_write_disk
99 This interface is deliberately very similar to the
101 interface used to write objects to a streaming archive.
102 .Bl -tag -width indent
103 .It Fn archive_write_disk_new
104 Allocates and initializes a
106 object suitable for writing objects to disk.
107 .It Fn archive_write_disk_set_skip_file
108 Records the device and inode numbers of a file that should not be
110 This is typically used to ensure that an extraction process does not
111 overwrite the archive from which objects are being read.
112 This capability is technically unnecessary but can be a significant
113 performance optimization in practice.
114 .It Fn archive_write_disk_set_options
115 The options field consists of a bitwise OR of one or more of the
117 .Bl -tag -compact -width "indent"
118 .It Cm ARCHIVE_EXTRACT_OWNER
119 The user and group IDs should be set on the restored file.
120 By default, the user and group IDs are not restored.
121 .It Cm ARCHIVE_EXTRACT_PERM
122 Full permissions (including SGID, SUID, and sticky bits) should
123 be restored exactly as specified, without obeying the
125 Note that SUID and SGID bits can only be restored if the
126 user and group ID of the object on disk are correct.
128 .Cm ARCHIVE_EXTRACT_OWNER
129 is not specified, then SUID and SGID bits will only be restored
130 if the default user and group IDs of newly-created objects on disk
131 happen to match those specified in the archive entry.
132 By default, only basic permissions are restored, and umask is obeyed.
133 .It Cm ARCHIVE_EXTRACT_TIME
134 The timestamps (mtime, ctime, and atime) should be restored.
135 By default, they are ignored.
136 Note that restoring of atime is not currently supported.
137 .It Cm ARCHIVE_EXTRACT_NO_OVERWRITE
138 Existing files on disk will not be overwritten.
139 By default, existing regular files are truncated and overwritten;
140 existing directories will have their permissions updated;
141 other pre-existing objects are unlinked and recreated from scratch.
142 .It Cm ARCHIVE_EXTRACT_UNLINK
143 Existing files on disk will be unlinked before any attempt to
145 In some cases, this can prove to be a significant performance improvement.
146 By default, existing files are truncated and rewritten, but
147 the file is not recreated.
148 In particular, the default behavior does not break existing hard links.
149 .It Cm ARCHIVE_EXTRACT_ACL
150 Attempt to restore ACLs.
151 By default, extended ACLs are ignored.
152 .It Cm ARCHIVE_EXTRACT_FFLAGS
153 Attempt to restore extended file flags.
154 By default, file flags are ignored.
155 .It Cm ARCHIVE_EXTRACT_XATTR
156 Attempt to restore POSIX.1e extended attributes.
157 By default, they are ignored.
158 .It Cm ARCHIVE_EXTRACT_SECURE_SYMLINKS
159 Refuse to extract any object whose final location would be altered
160 by a symlink on disk.
161 This is intended to help guard against a variety of mischief
162 caused by archives that (deliberately or otherwise) extract
163 files outside of the current directory.
164 The default is not to perform this check.
166 .Cm ARCHIVE_EXTRACT_UNLINK
167 is specified together with this option, the library will
168 remove any intermediate symlinks it finds and return an
169 error only if such symlink could not be removed.
170 .It Cm ARCHIVE_EXTRACT_SECURE_NODOTDOT
171 Refuse to extract a path that contains a
173 element anywhere within it.
174 The default is to not refuse such paths.
175 Note that paths ending in
177 always cause an error, regardless of this flag.
178 .It Cm ARCHIVE_EXTRACT_SPARSE
179 Scan data for blocks of NUL bytes and try to recreate them with holes.
180 This results in sparse files, independent of whether the archive format
181 supports or uses them.
184 .Fn archive_write_disk_set_group_lookup ,
185 .Fn archive_write_disk_set_user_lookup
188 .Tn struct archive_entry
189 objects contain both names and ids that can be used to identify users
191 These names and ids describe the ownership of the file itself and
192 also appear in ACL lists.
193 By default, the library uses the ids and ignores the names, but
194 this can be overridden by registering user and group lookup functions.
195 To register, you must provide a lookup function which
196 accepts both a name and id and returns a suitable id.
197 You may also provide a
199 pointer to a private data structure and a cleanup function for
201 The cleanup function will be invoked when the
204 .It Fn archive_write_disk_set_standard_lookup
205 This convenience function installs a standard set of user
206 and group lookup functions.
211 to convert names to ids, defaulting to the ids if the names cannot
213 These functions also implement a simple memory cache to reduce
214 the number of calls to
218 .It Fn archive_write_header
219 Build and write a header using the data in the provided
220 .Tn struct archive_entry
224 for information on creating and populating
225 .Tn struct archive_entry
227 .It Fn archive_write_data
228 Write data corresponding to the header just written.
229 Returns number of bytes written or -1 on error.
230 .It Fn archive_write_data_block
231 Write data corresponding to the header just written.
233 .Fn archive_write_data
234 except that it performs a seek on the file being
235 written to the specified offset before writing the data.
236 This is useful when restoring sparse files from archive
237 formats that support sparse files.
238 Returns number of bytes written or -1 on error.
239 (Note: This is currently not supported for
242 .Tn archive_write_disk
244 .It Fn archive_write_finish_entry
245 Close out the entry just written.
246 Ordinarily, clients never need to call this, as it
247 is called automatically by
248 .Fn archive_write_next_header
250 .Fn archive_write_close
252 However, some file attributes are written to disk only
253 after the file is closed, so this can be necessary
254 if you need to work with the file on disk right away.
255 .It Fn archive_write_close
256 Set any attributes that could not be set during the initial restore.
257 For example, directory timestamps are not restored initially because
258 restoring a subsequent file would alter that timestamp.
259 Similarly, non-writable directories are initially created with
260 write permissions (so that their contents can be restored).
263 library maintains a list of all such deferred attributes and
264 sets them when this function is invoked.
265 .It Fn archive_write_finish
266 This is a deprecated synonym for
267 .Fn archive_write_free .
268 .It Fn archive_write_free
270 .Fn archive_write_close
271 if it was not invoked manually, then releases all resources.
273 More information about the
275 object and the overall design of the library can be found in the
278 Many of these functions are also documented under
279 .Xr archive_write 3 .
281 Most functions return
283 (zero) on success, or one of several non-zero
284 error codes for errors.
285 Specific error codes include:
287 for operations that might succeed if retried,
289 for unusual conditions that do not prevent further operations, and
291 for serious errors that make remaining operations impossible.
293 .Fn archive_write_disk_new
294 returns a pointer to a newly-allocated
298 .Fn archive_write_data
299 returns a count of the number of bytes actually written,
305 Detailed error codes and textual descriptions are available from the
308 .Fn archive_error_string
313 .Xr archive_write 3 ,
319 library first appeared in
322 .Nm archive_write_disk
323 interface was added to
325 and first appeared in
331 library was written by
332 .An Tim Kientzle Aq kientzle@acm.org .
334 Directories are actually extracted in two distinct phases.
335 Directories are created during
336 .Fn archive_write_header ,
337 but final permissions are not set until
338 .Fn archive_write_close .
339 This separation is necessary to correctly handle borderline
340 cases such as a non-writable directory containing
341 files, but can cause unexpected results.
342 In particular, directory permissions are not fully
343 restored until the archive is closed.
346 to change the current directory between calls to
347 .Fn archive_read_extract
349 .Fn archive_read_close ,
350 you may confuse the permission-setting logic with
351 the result that directory permissions are restored
354 The library attempts to create objects with filenames longer than
356 by creating prefixes of the full path and changing the current directory.
357 Currently, this logic is limited in scope; the fixup pass does
358 not work correctly for such objects and the symlink security check
359 option disables the support for very long pathnames.
363 does create each intermediate directory.
364 In particular, the directory
366 is created as well as the final object
368 In theory, this can be exploited to create an entire directory hierarchy
369 with a single request.
370 Of course, this does not work if the
371 .Cm ARCHIVE_EXTRACT_NODOTDOT
374 Implicit directories are always created obeying the current umask.
375 Explicit objects are created obeying the current umask unless
376 .Cm ARCHIVE_EXTRACT_PERM
377 is specified, in which case they current umask is ignored.
379 SGID and SUID bits are restored only if the correct user and
382 .Cm ARCHIVE_EXTRACT_OWNER
383 is not specified, then no attempt is made to set the ownership.
384 In this case, SGID and SUID bits are restored only if the
385 user and group of the final object happen to match those specified
390 user-id and group-id lookup functions are not the defaults because
394 are sometimes too large for particular applications.
395 The current design allows the application author to use a more
396 compact implementation when appropriate.
398 There should be a corresponding
399 .Nm archive_read_disk
400 interface that walks a directory hierarchy and returns archive