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28 .Dt ARCHIVE_READ_DISK 3
31 .Nm archive_read_disk_new ,
32 .Nm archive_read_disk_set_symlink_logical ,
33 .Nm archive_read_disk_set_symlink_physical ,
34 .Nm archive_read_disk_set_symlink_hybrid ,
35 .Nm archive_read_disk_entry_from_file ,
36 .Nm archive_read_disk_gname ,
37 .Nm archive_read_disk_uname ,
38 .Nm archive_read_disk_set_uname_lookup ,
39 .Nm archive_read_disk_set_gname_lookup ,
40 .Nm archive_read_disk_set_standard_lookup
41 .Nd functions for reading objects from disk
43 Streaming Archive Library (libarchive, -larchive)
47 .Fn archive_read_disk_new "void"
49 .Fn archive_read_disk_set_symlink_logical "struct archive *"
51 .Fn archive_read_disk_set_symlink_physical "struct archive *"
53 .Fn archive_read_disk_set_symlink_hybrid "struct archive *"
55 .Fn archive_read_disk_gname "struct archive *" "gid_t"
57 .Fn archive_read_disk_uname "struct archive *" "uid_t"
59 .Fo archive_read_disk_set_gname_lookup
60 .Fa "struct archive *"
62 .Fa "const char *(*lookup)(void *, gid_t)"
63 .Fa "void (*cleanup)(void *)"
66 .Fo archive_read_disk_set_uname_lookup
67 .Fa "struct archive *"
69 .Fa "const char *(*lookup)(void *, uid_t)"
70 .Fa "void (*cleanup)(void *)"
73 .Fn archive_read_disk_set_standard_lookup "struct archive *"
75 .Fo archive_read_disk_entry_from_file
76 .Fa "struct archive *"
77 .Fa "struct archive_entry *"
79 .Fa "const struct stat *"
82 These functions provide an API for reading information about
84 In particular, they provide an interface for populating
85 .Tn struct archive_entry
87 .Bl -tag -width indent
88 .It Fn archive_read_disk_new
89 Allocates and initializes a
91 object suitable for reading object information from disk.
93 .Fn archive_read_disk_set_symlink_logical ,
94 .Fn archive_read_disk_set_symlink_physical ,
95 .Fn archive_read_disk_set_symlink_hybrid
97 This sets the mode used for handling symbolic links.
100 mode follows all symbolic links.
103 mode does not follow any symbolic links.
106 mode currently behaves identically to the
110 .Fn archive_read_disk_gname ,
111 .Fn archive_read_disk_uname
113 Returns a user or group name given a gid or uid value.
114 By default, these always return a NULL string.
116 .Fn archive_read_disk_set_gname_lookup ,
117 .Fn archive_read_disk_set_uname_lookup
119 These allow you to override the functions used for
120 user and group name lookups.
121 You may also provide a
123 pointer to a private data structure and a cleanup function for
125 The cleanup function will be invoked when the
127 object is destroyed or when new lookup functions are registered.
128 .It Fn archive_read_disk_set_standard_lookup
129 This convenience function installs a standard set of user
130 and group name lookup functions.
135 to convert ids to names, defaulting to NULL if the names cannot
137 These functions also implement a simple memory cache to reduce
138 the number of calls to
142 .It Fn archive_read_disk_entry_from_file
144 .Tn struct archive_entry
145 object with information about a particular file.
148 object must have already been created with
149 .Xr archive_entry_new 3
150 and at least one of the source path or path fields must already be set.
151 (If both are set, the source path will be used.)
153 Information is read from disk using the path name from the
154 .Tn struct archive_entry
156 If a file descriptor is provided, some information will be obtained using
157 that file descriptor, on platforms that support the appropriate
162 is provided, information from that structure will be used instead
163 of reading from the disk where appropriate.
164 This can provide performance benefits in scenarios where
166 information has already been read from the disk as a side effect
167 of some other operation.
168 (For example, directory traversal libraries often provide this information.)
170 Where necessary, user and group ids are converted to user and group names
171 using the currently registered lookup functions above.
172 This affects the file ownership fields and ACL values in the
173 .Tn struct archive_entry
176 More information about the
178 object and the overall design of the library can be found in the
182 The following illustrates basic usage of the library by
183 showing how to use it to copy an item on disk into an archive.
184 .Bd -literal -offset indent
186 file_to_archive(struct archive *a, const char *name)
191 struct archive_entry *entry;
194 ard = archive_read_disk_new();
195 archive_read_disk_set_standard_lookup(ard);
196 entry = archive_entry_new();
197 fd = open(name, O_RDONLY);
200 archive_entry_copy_pathname(entry, name);
201 archive_read_disk_entry_from_file(ard, entry, fd, NULL);
202 archive_write_header(a, entry);
203 while ((bytes_read = read(fd, buff, sizeof(buff))) > 0)
204 archive_write_data(a, buff, bytes_read);
205 archive_write_finish_entry(a);
206 archive_read_free(ard);
207 archive_entry_free(entry);
211 Most functions return
213 (zero) on success, or one of several negative
214 error codes for errors.
215 Specific error codes include:
217 for operations that might succeed if retried,
219 for unusual conditions that do not prevent further operations, and
221 for serious errors that make remaining operations impossible.
223 .Fn archive_read_disk_new
224 returns a pointer to a newly-allocated
226 object or NULL if the allocation failed for any reason.
228 .Fn archive_read_disk_gname
230 .Fn archive_read_disk_uname
233 pointers to the textual name or NULL if the lookup failed for any reason.
234 The returned pointer points to internal storage that
235 may be reused on the next call to either of these functions;
236 callers should copy the string if they need to continue accessing it.
239 Detailed error codes and textual descriptions are available from the
242 .Fn archive_error_string
248 .Xr archive_write 3 ,
249 .Xr archive_write_disk 3 ,
255 library first appeared in
258 .Nm archive_read_disk
259 interface was added to
261 and first appeared in
267 library was written by
268 .An Tim Kientzle Aq kientzle@FreeBSD.org .
272 user name and group name lookup functions are not the defaults because
276 are sometimes too large for particular applications.
277 The current design allows the application author to use a more
278 compact implementation when appropriate.
280 The full list of metadata read from disk by
281 .Fn archive_read_disk_entry_from_file
282 is necessarily system-dependent.
285 .Fn archive_read_disk_entry_from_file
286 function reads as much information as it can from disk.
287 Some method should be provided to limit this so that clients who
288 do not need ACLs, for instance, can avoid the extra work needed
289 to look up such information.
291 This API should provide a set of methods for walking a directory tree.
292 That would make it a direct parallel of the
295 When such methods are implemented, the
297 symbolic link mode will make sense.