1 .\" Copyright (c) 2003-2007 Tim Kientzle
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
13 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 .Nm archive_write_new ,
32 .Nm archive_write_set_format_cpio ,
33 .Nm archive_write_set_format_pax ,
34 .Nm archive_write_set_format_pax_restricted ,
35 .Nm archive_write_set_format_shar ,
36 .Nm archive_write_set_format_shar_binary ,
37 .Nm archive_write_set_format_ustar ,
38 .Nm archive_write_get_bytes_per_block ,
39 .Nm archive_write_set_bytes_per_block ,
40 .Nm archive_write_set_bytes_in_last_block ,
41 .Nm archive_write_set_compression_bzip2 ,
42 .Nm archive_write_set_compression_gzip ,
43 .Nm archive_write_set_compression_none ,
44 .Nm archive_write_set_compression_program ,
45 .Nm archive_write_open ,
46 .Nm archive_write_open_fd ,
47 .Nm archive_write_open_FILE ,
48 .Nm archive_write_open_filename ,
49 .Nm archive_write_open_memory ,
50 .Nm archive_write_header ,
51 .Nm archive_write_data ,
52 .Nm archive_write_finish_entry ,
53 .Nm archive_write_close ,
54 .Nm archive_write_finish
55 .Nd functions for creating archives
59 .Fn archive_write_new "void"
61 .Fn archive_write_get_bytes_per_block "struct archive *"
63 .Fn archive_write_set_bytes_per_block "struct archive *" "int bytes_per_block"
65 .Fn archive_write_set_bytes_in_last_block "struct archive *" "int"
67 .Fn archive_write_set_compression_bzip2 "struct archive *"
69 .Fn archive_write_set_compression_gzip "struct archive *"
71 .Fn archive_write_set_compression_none "struct archive *"
73 .Fo archive_write_set_compression_program
74 .Fa "struct archive *"
75 .Fa "const char * cmd"
78 .Fn archive_write_set_format_cpio "struct archive *"
80 .Fn archive_write_set_format_pax "struct archive *"
82 .Fn archive_write_set_format_pax_restricted "struct archive *"
84 .Fn archive_write_set_format_shar "struct archive *"
86 .Fn archive_write_set_format_shar_binary "struct archive *"
88 .Fn archive_write_set_format_ustar "struct archive *"
90 .Fo archive_write_open
91 .Fa "struct archive *"
92 .Fa "void *client_data"
93 .Fa "archive_open_callback *"
94 .Fa "archive_write_callback *"
95 .Fa "archive_close_callback *"
98 .Fn archive_write_open_fd "struct archive *" "int fd"
100 .Fn archive_write_open_FILE "struct archive *" "FILE *file"
102 .Fn archive_write_open_filename "struct archive *" "const char *filename"
104 .Fo archive_write_open_memory
105 .Fa "struct archive *"
107 .Fa "size_t bufferSize"
108 .Fa "size_t *outUsed"
111 .Fn archive_write_header "struct archive *" "struct archive_entry *"
113 .Fn archive_write_data "struct archive *" "const void *" "size_t"
115 .Fn archive_write_finish_entry "struct archive *"
117 .Fn archive_write_close "struct archive *"
119 .Fn archive_write_finish "struct archive *"
121 These functions provide a complete API for creating streaming
123 The general process is to first create the
125 object, set any desired options, initialize the archive, append entries, then
126 close the archive and release all resources.
127 The following summary describes the functions in approximately
128 the order they are ordinarily used:
129 .Bl -tag -width indent
130 .It Fn archive_write_new
131 Allocates and initializes a
133 object suitable for writing a tar archive.
134 .It Fn archive_write_set_bytes_per_block
135 Sets the block size used for writing the archive data.
136 Every call to the write callback function, except possibly the last one, will
137 use this value for the length.
138 The third parameter is a boolean that specifies whether or not the final block
139 written will be padded to the full block size.
140 If it is zero, the last block will not be padded.
141 If it is non-zero, padding will be added both before and after compression.
142 The default is to use a block size of 10240 bytes and to pad the last block.
143 Note that a block size of zero will suppress internal blocking
144 and cause writes to be sent directly to the write callback as they occur.
145 .It Fn archive_write_get_bytes_per_block
146 Retrieve the block size to be used for writing.
147 A value of -1 here indicates that the library should use default values.
148 A value of zero indicates that internal blocking is suppressed.
149 .It Fn archive_write_set_bytes_in_last_block
150 Sets the block size used for writing the last block.
151 If this value is zero, the last block will be padded to the same size
153 Otherwise, the final block will be padded to a multiple of this size.
154 In particular, setting it to 1 will cause the final block to not be padded.
155 For compressed output, any padding generated by this option
156 is applied only after the compression.
157 The uncompressed data is always unpadded.
158 The default is to pad the last block to the full block size (note that
159 .Fn archive_write_open_filename
160 will set this based on the file type).
163 functions, this function can be called after the archive is opened.
164 .It Fn archive_write_get_bytes_in_last_block
165 Retrieve the currently-set value for last block size.
166 A value of -1 here indicates that the library should use default values.
168 .Fn archive_write_set_format_cpio ,
169 .Fn archive_write_set_format_pax ,
170 .Fn archive_write_set_format_pax_restricted ,
171 .Fn archive_write_set_format_shar ,
172 .Fn archive_write_set_format_shar_binary ,
173 .Fn archive_write_set_format_ustar
175 Sets the format that will be used for the archive.
176 The library can write
177 POSIX octet-oriented cpio format archives,
186 shar archives that store a variety of file attributes and handle binary files,
191 The pax interchange format is a backwards-compatible tar format that
192 adds key/value attributes to each entry and supports arbitrary
193 filenames, linknames, uids, sizes, etc.
194 .Dq Restricted pax interchange format
195 is the library default; this is the same as pax format, but suppresses
196 the pax extended header for most normal files.
197 In most cases, this will result in ordinary ustar archives.
199 .Fn archive_write_set_compression_bzip2 ,
200 .Fn archive_write_set_compression_gzip ,
201 .Fn archive_write_set_compression_none
203 The resulting archive will be compressed as specified.
204 Note that the compressed output is always properly blocked.
205 .It Fn archive_write_set_compression_program
206 The archive will be fed into the specified compression program.
207 The output of that program is blocked and written to the client
209 .It Fn archive_write_open
210 Freeze the settings, open the archive, and prepare for writing entries.
211 This is the most generic form of this function, which accepts
212 pointers to three callback functions which will be invoked by
213 the compression layer to write the constructed archive.
214 .It Fn archive_write_open_fd
215 A convenience form of
216 .Fn archive_write_open
217 that accepts a file descriptor.
219 .Fn archive_write_open_fd
220 function is safe for use with tape drives or other
221 block-oriented devices.
222 .It Fn archive_write_open_FILE
223 A convenience form of
224 .Fn archive_write_open
229 .Fn archive_write_open_FILE
230 is not safe for writing to tape drives or other devices
231 that require correct blocking.
232 .It Fn archive_write_open_file
233 A deprecated synonym for
234 .Fn archive_write_open_filename .
235 .It Fn archive_write_open_filename
236 A convenience form of
237 .Fn archive_write_open
238 that accepts a filename.
239 A NULL argument indicates that the output should be written to standard output;
242 will open a file with that name.
243 If you have not invoked
244 .Fn archive_write_set_bytes_in_last_block ,
246 .Fn archive_write_open_filename
247 will adjust the last-block padding depending on the file:
248 it will enable padding when writing to standard output or
249 to a character or block device node, it will disable padding otherwise.
250 You can override this by manually invoking
251 .Fn archive_write_set_bytes_in_last_block
253 .Fn archive_write_open .
255 .Fn archive_write_open_filename
256 function is safe for use with tape drives or other
257 block-oriented devices.
258 .It Fn archive_write_open_memory
259 A convenience form of
260 .Fn archive_write_open
261 that accepts a pointer to a block of memory that will receive
265 argument points to a variable that will be updated
266 after each write to reflect how much of the buffer
268 You should be careful to ensure that this variable
269 remains allocated until after the archive is
271 .It Fn archive_write_header
272 Build and write a header using the data in the provided
273 .Tn struct archive_entry
277 for information on creating and populating
278 .Tn struct archive_entry
280 .It Fn archive_write_data
281 Write data corresponding to the header just written.
282 Returns number of bytes written or -1 on error.
283 .It Fn archive_write_finish_entry
284 Close out the entry just written.
285 In particular, this writes out the final padding required by some formats.
286 Ordinarily, clients never need to call this, as it
287 is called automatically by
288 .Fn archive_write_next_header
290 .Fn archive_write_close
292 .It Fn archive_write_close
293 Complete the archive and invoke the close callback.
294 .It Fn archive_write_finish
296 .Fn archive_write_close
297 if it was not invoked manually, then releases all resources.
298 Note that this function was declared to return
300 in libarchive 1.x, which made it impossible to detect errors when
301 .Fn archive_write_close
302 was invoked implicitly from this function.
303 This is corrected beginning with libarchive 2.0.
305 More information about the
307 object and the overall design of the library can be found in the
311 Compression support is built-in to libarchive, which uses zlib and bzlib
312 to handle gzip and bzip2 compression, respectively.
314 To use this library, you will need to define and register
315 callback functions that will be invoked to write data to the
317 These functions are registered by calling
318 .Fn archive_write_open :
319 .Bl -item -offset indent
322 .Fn archive_open_callback "struct archive *" "void *client_data"
325 The open callback is invoked by
326 .Fn archive_write_open .
329 if the underlying file or data source is successfully
331 If the open fails, it should call
332 .Fn archive_set_error
333 to register an error code and message and return
335 .Bl -item -offset indent
338 .Fo archive_write_callback
339 .Fa "struct archive *"
340 .Fa "void *client_data"
346 The write callback is invoked whenever the library
347 needs to write raw bytes to the archive.
348 For correct blocking, each call to the write callback function
349 should translate into a single
352 This is especially critical when writing archives to tape drives.
353 On success, the write callback should return the
354 number of bytes actually written.
355 On error, the callback should invoke
356 .Fn archive_set_error
357 to register an error code and message and return -1.
358 .Bl -item -offset indent
361 .Fn archive_close_callback "struct archive *" "void *client_data"
364 The close callback is invoked by archive_close when
365 the archive processing is complete.
366 The callback should return
369 On failure, the callback should invoke
370 .Fn archive_set_error
371 to register an error code and message and
375 The following sketch illustrates basic usage of the library.
377 the callback functions are simply wrappers around the standard
383 .Bd -literal -offset indent
384 #include <sys/stat.h>
386 #include <archive_entry.h>
397 myopen(struct archive *a, void *client_data)
399 struct mydata *mydata = client_data;
401 mydata->fd = open(mydata->name, O_WRONLY | O_CREAT, 0644);
405 return (ARCHIVE_FATAL);
409 mywrite(struct archive *a, void *client_data, void *buff, size_t n)
411 struct mydata *mydata = client_data;
413 return (write(mydata->fd, buff, n));
417 myclose(struct archive *a, void *client_data)
419 struct mydata *mydata = client_data;
427 write_archive(const char *outname, const char **filename)
429 struct mydata *mydata = malloc(sizeof(struct mydata));
431 struct archive_entry *entry;
437 a = archive_write_new();
438 mydata->name = outname;
439 archive_write_set_compression_gzip(a);
440 archive_write_set_format_ustar(a);
441 archive_write_open(a, mydata, myopen, mywrite, myclose);
443 stat(*filename, &st);
444 entry = archive_entry_new();
445 archive_entry_copy_stat(entry, &st);
446 archive_entry_set_pathname(entry, *filename);
447 archive_write_header(a, entry);
448 fd = open(*filename, O_RDONLY);
449 len = read(fd, buff, sizeof(buff));
451 archive_write_data(a, buff, len);
452 len = read(fd, buff, sizeof(buff));
454 archive_entry_free(entry);
457 archive_write_finish(a);
460 int main(int argc, const char **argv)
465 write_archive(outname, argv);
470 Most functions return
472 (zero) on success, or one of several non-zero
473 error codes for errors.
474 Specific error codes include:
476 for operations that might succeed if retried,
478 for unusual conditions that do not prevent further operations, and
480 for serious errors that make remaining operations impossible.
484 .Fn archive_error_string
485 functions can be used to retrieve an appropriate error code and a
486 textual error message.
488 .Fn archive_write_new
489 returns a pointer to a newly-allocated
493 .Fn archive_write_data
494 returns a count of the number of bytes actually written.
495 On error, -1 is returned and the
498 .Fn archive_error_string
499 functions will return appropriate values.
500 Note that if the client-provided write callback function
501 returns a non-zero value, that error will be propagated back to the caller
502 through whatever API function resulted in that call, which
504 .Fn archive_write_header ,
505 .Fn archive_write_data ,
506 .Fn archive_write_close ,
508 .Fn archive_write_finish .
509 The client callback can call
510 .Fn archive_set_error
511 to provide values that can then be retrieved by
514 .Fn archive_error_string .
522 library first appeared in
528 library was written by
529 .An Tim Kientzle Aq kientzle@acm.org .
531 There are many peculiar bugs in historic tar implementations that may cause
532 certain programs to reject archives written by this library.
533 For example, several historic implementations calculated header checksums
534 incorrectly and will thus reject valid archives; GNU tar does not fully support
535 pax interchange format; some old tar implementations required specific
538 The default pax interchange format eliminates most of the historic
539 tar limitations and provides a generic key/value attribute facility
540 for vendor-defined extensions.
541 One oversight in POSIX is the failure to provide a standard attribute
542 for large device numbers.
547 for device numbers that exceed the range supported by the backwards-compatible
549 These keys are compatible with Joerg Schilling's
552 Other implementations may not recognize these keys and will thus be unable
553 to correctly restore device nodes with large device numbers from archives
554 created by this library.