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28 .Dt ARCHIVE_READ_DISK 3
31 .Nm archive_read_disk_new ,
32 .Nm archive_read_disk_set_behavior ,
33 .Nm archive_read_disk_set_symlink_logical ,
34 .Nm archive_read_disk_set_symlink_physical ,
35 .Nm archive_read_disk_set_symlink_hybrid ,
36 .Nm archive_read_disk_entry_from_file ,
37 .Nm archive_read_disk_gname ,
38 .Nm archive_read_disk_uname ,
39 .Nm archive_read_disk_set_uname_lookup ,
40 .Nm archive_read_disk_set_gname_lookup ,
41 .Nm archive_read_disk_set_standard_lookup
42 .Nd functions for reading objects from disk
44 Streaming Archive Library (libarchive, -larchive)
48 .Fn archive_read_disk_new "void"
50 .Fn archive_read_disk_set_behavior "struct archive *" "int"
52 .Fn archive_read_disk_set_symlink_logical "struct archive *"
54 .Fn archive_read_disk_set_symlink_physical "struct archive *"
56 .Fn archive_read_disk_set_symlink_hybrid "struct archive *"
58 .Fn archive_read_disk_gname "struct archive *" "gid_t"
60 .Fn archive_read_disk_uname "struct archive *" "uid_t"
62 .Fo archive_read_disk_set_gname_lookup
63 .Fa "struct archive *"
65 .Fa "const char *(*lookup)(void *, gid_t)"
66 .Fa "void (*cleanup)(void *)"
69 .Fo archive_read_disk_set_uname_lookup
70 .Fa "struct archive *"
72 .Fa "const char *(*lookup)(void *, uid_t)"
73 .Fa "void (*cleanup)(void *)"
76 .Fn archive_read_disk_set_standard_lookup "struct archive *"
78 .Fo archive_read_disk_entry_from_file
79 .Fa "struct archive *"
80 .Fa "struct archive_entry *"
82 .Fa "const struct stat *"
85 These functions provide an API for reading information about
87 In particular, they provide an interface for populating
88 .Tn struct archive_entry
90 .Bl -tag -width indent
91 .It Fn archive_read_disk_new
92 Allocates and initializes a
94 object suitable for reading object information from disk.
95 .It Fn archive_read_disk_set_behavior
96 Configures various behavior options when reading entries from disk.
97 The flags field consists of a bitwise OR of one or more of the
99 .Bl -tag -compact -width "indent"
100 .It Cm ARCHIVE_READDISK_HONOR_NODUMP
101 Skip files and directories with the nodump file attribute (file flag) set.
102 By default, the nodump file attribute is ignored.
103 .It Cm ARCHIVE_READDISK_MAC_COPYFILE
105 Read metadata (ACLs and extended attributes) with
107 By default, metadata is read using
109 .It Cm ARCHIVE_READDISK_NO_ACL
110 Do not read Access Control Lists.
111 By default, ACLs are read from disk.
112 .It Cm ARCHIVE_READDISK_NO_FFLAGS
113 Do not read file attributes (file flags).
114 By default, file attributes are read from disk.
120 .Pq FreeBSD, Mac OS X
121 for more information on file attributes.
122 .It Cm ARCHIVE_READDISK_NO_TRAVERSE_MOUNTS
123 Do not traverse mount points.
124 By default, mount points are traversed.
125 .It Cm ARCHIVE_READDISK_NO_XATTR
126 Do not read extended file attributes (xattrs).
127 By default, extended file attributes are read from disk.
136 for more information on extended file attributes.
137 .It Cm ARCHIVE_READDISK_RESTORE_ATIME
138 Restore access time of traversed files.
139 By default, access time of traversed files is not restored.
142 .Fn archive_read_disk_set_symlink_logical ,
143 .Fn archive_read_disk_set_symlink_physical ,
144 .Fn archive_read_disk_set_symlink_hybrid
146 This sets the mode used for handling symbolic links.
149 mode follows all symbolic links.
152 mode does not follow any symbolic links.
155 mode currently behaves identically to the
159 .Fn archive_read_disk_gname ,
160 .Fn archive_read_disk_uname
162 Returns a user or group name given a gid or uid value.
163 By default, these always return a NULL string.
165 .Fn archive_read_disk_set_gname_lookup ,
166 .Fn archive_read_disk_set_uname_lookup
168 These allow you to override the functions used for
169 user and group name lookups.
170 You may also provide a
172 pointer to a private data structure and a cleanup function for
174 The cleanup function will be invoked when the
176 object is destroyed or when new lookup functions are registered.
177 .It Fn archive_read_disk_set_standard_lookup
178 This convenience function installs a standard set of user
179 and group name lookup functions.
184 to convert ids to names, defaulting to NULL if the names cannot
186 These functions also implement a simple memory cache to reduce
187 the number of calls to
191 .It Fn archive_read_disk_entry_from_file
193 .Tn struct archive_entry
194 object with information about a particular file.
197 object must have already been created with
198 .Xr archive_entry_new 3
199 and at least one of the source path or path fields must already be set.
200 (If both are set, the source path will be used.)
202 Information is read from disk using the path name from the
203 .Tn struct archive_entry
205 If a file descriptor is provided, some information will be obtained using
206 that file descriptor, on platforms that support the appropriate
211 is provided, information from that structure will be used instead
212 of reading from the disk where appropriate.
213 This can provide performance benefits in scenarios where
215 information has already been read from the disk as a side effect
216 of some other operation.
217 (For example, directory traversal libraries often provide this information.)
219 Where necessary, user and group ids are converted to user and group names
220 using the currently-registered lookup functions above.
221 This affects the file ownership fields and ACL values in the
222 .Tn struct archive_entry
225 More information about the
227 object and the overall design of the library can be found in the
231 The following illustrates basic usage of the library by
232 showing how to use it to copy an item on disk into an archive.
233 .Bd -literal -offset indent
235 file_to_archive(struct archive *a, const char *name)
240 struct archive_entry *entry;
243 ard = archive_read_disk_new();
244 archive_read_disk_set_standard_lookup(ard);
245 entry = archive_entry_new();
246 fd = open(name, O_RDONLY);
249 archive_entry_copy_pathname(entry, name);
250 archive_read_disk_entry_from_file(ard, entry, fd, NULL);
251 archive_write_header(a, entry);
252 while ((bytes_read = read(fd, buff, sizeof(buff))) > 0)
253 archive_write_data(a, buff, bytes_read);
254 archive_write_finish_entry(a);
255 archive_read_free(ard);
256 archive_entry_free(entry);
260 Most functions return
262 (zero) on success, or one of several negative
263 error codes for errors.
264 Specific error codes include:
266 for operations that might succeed if retried,
268 for unusual conditions that do not prevent further operations, and
270 for serious errors that make remaining operations impossible.
272 .Fn archive_read_disk_new
273 returns a pointer to a newly-allocated
275 object or NULL if the allocation failed for any reason.
277 .Fn archive_read_disk_gname
279 .Fn archive_read_disk_uname
282 pointers to the textual name or NULL if the lookup failed for any reason.
283 The returned pointer points to internal storage that
284 may be reused on the next call to either of these functions;
285 callers should copy the string if they need to continue accessing it.
288 Detailed error codes and textual descriptions are available from the
291 .Fn archive_error_string
298 .Xr archive_write 3 ,
299 .Xr archive_write_disk 3 ,
304 library first appeared in
307 .Nm archive_read_disk
308 interface was added to
310 and first appeared in
316 library was written by
317 .An Tim Kientzle Aq kientzle@FreeBSD.org .
321 user name and group name lookup functions are not the defaults because
325 are sometimes too large for particular applications.
326 The current design allows the application author to use a more
327 compact implementation when appropriate.
329 The full list of metadata read from disk by
330 .Fn archive_read_disk_entry_from_file
331 is necessarily system-dependent.
334 .Fn archive_read_disk_entry_from_file
335 function reads as much information as it can from disk.
336 Some method should be provided to limit this so that clients who
337 do not need ACLs, for instance, can avoid the extra work needed
338 to look up such information.
340 This API should provide a set of methods for walking a directory tree.
341 That would make it a direct parallel of the
344 When such methods are implemented, the
346 symbolic link mode will make sense.