1 archive_write(3) FreeBSD Library Functions Manual archive_write(3)
4 archive_write_new, archive_write_set_format_cpio,
5 archive_write_set_format_pax, archive_write_set_format_pax_restricted,
6 archive_write_set_format_shar, archive_write_set_format_shar_binary,
7 archive_write_set_format_ustar, archive_write_get_bytes_per_block,
8 archive_write_set_bytes_per_block, archive_write_set_bytes_in_last_block,
9 archive_write_set_compression_bzip2,
10 archive_write_set_compression_compress,
11 archive_write_set_compression_gzip, archive_write_set_compression_none,
12 archive_write_set_compression_program, archive_write_open,
13 archive_write_open_fd, archive_write_open_FILE,
14 archive_write_open_filename, archive_write_open_memory,
15 archive_write_header, archive_write_data, archive_write_finish_entry,
16 archive_write_close, archive_write_finish -- functions for creating ar-
23 archive_write_new(void);
26 archive_write_get_bytes_per_block(struct archive *);
29 archive_write_set_bytes_per_block(struct archive *, int bytes_per_block);
32 archive_write_set_bytes_in_last_block(struct archive *, int);
35 archive_write_set_compression_bzip2(struct archive *);
38 archive_write_set_compression_compress(struct archive *);
41 archive_write_set_compression_gzip(struct archive *);
44 archive_write_set_compression_none(struct archive *);
47 archive_write_set_compression_program(struct archive *,
51 archive_write_set_format_cpio(struct archive *);
54 archive_write_set_format_pax(struct archive *);
57 archive_write_set_format_pax_restricted(struct archive *);
60 archive_write_set_format_shar(struct archive *);
63 archive_write_set_format_shar_binary(struct archive *);
66 archive_write_set_format_ustar(struct archive *);
69 archive_write_open(struct archive *, void *client_data,
70 archive_open_callback *, archive_write_callback *,
71 archive_close_callback *);
74 archive_write_open_fd(struct archive *, int fd);
77 archive_write_open_FILE(struct archive *, FILE *file);
80 archive_write_open_filename(struct archive *, const char *filename);
83 archive_write_open_memory(struct archive *, void *buffer,
84 size_t bufferSize, size_t *outUsed);
87 archive_write_header(struct archive *, struct archive_entry *);
90 archive_write_data(struct archive *, const void *, size_t);
93 archive_write_finish_entry(struct archive *);
96 archive_write_close(struct archive *);
99 archive_write_finish(struct archive *);
102 These functions provide a complete API for creating streaming archive
103 files. The general process is to first create the struct archive object,
104 set any desired options, initialize the archive, append entries, then
105 close the archive and release all resources. The following summary
106 describes the functions in approximately the order they are ordinarily
110 Allocates and initializes a struct archive object suitable for
111 writing a tar archive.
113 archive_write_set_bytes_per_block()
114 Sets the block size used for writing the archive data. Every
115 call to the write callback function, except possibly the last
116 one, will use this value for the length. The third parameter is
117 a boolean that specifies whether or not the final block written
118 will be padded to the full block size. If it is zero, the last
119 block will not be padded. If it is non-zero, padding will be
120 added both before and after compression. The default is to use a
121 block size of 10240 bytes and to pad the last block. Note that a
122 block size of zero will suppress internal blocking and cause
123 writes to be sent directly to the write callback as they occur.
125 archive_write_get_bytes_per_block()
126 Retrieve the block size to be used for writing. A value of -1
127 here indicates that the library should use default values. A
128 value of zero indicates that internal blocking is suppressed.
130 archive_write_set_bytes_in_last_block()
131 Sets the block size used for writing the last block. If this
132 value is zero, the last block will be padded to the same size as
133 the other blocks. Otherwise, the final block will be padded to a
134 multiple of this size. In particular, setting it to 1 will cause
135 the final block to not be padded. For compressed output, any
136 padding generated by this option is applied only after the com-
137 pression. The uncompressed data is always unpadded. The default
138 is to pad the last block to the full block size (note that
139 archive_write_open_filename() will set this based on the file
140 type). Unlike the other ``set'' functions, this function can be
141 called after the archive is opened.
143 archive_write_get_bytes_in_last_block()
144 Retrieve the currently-set value for last block size. A value of
145 -1 here indicates that the library should use default values.
147 archive_write_set_format_cpio(), archive_write_set_format_pax(),
148 archive_write_set_format_pax_restricted(),
149 archive_write_set_format_shar(),
150 archive_write_set_format_shar_binary(),
151 archive_write_set_format_ustar()
152 Sets the format that will be used for the archive. The library
153 can write POSIX octet-oriented cpio format archives, POSIX-stan-
154 dard ``pax interchange'' format archives, traditional ``shar''
155 archives, enhanced ``binary'' shar archives that store a variety
156 of file attributes and handle binary files, and POSIX-standard
157 ``ustar'' archives. The pax interchange format is a backwards-
158 compatible tar format that adds key/value attributes to each
159 entry and supports arbitrary filenames, linknames, uids, sizes,
160 etc. ``Restricted pax interchange format'' is the library
161 default; this is the same as pax format, but suppresses the pax
162 extended header for most normal files. In most cases, this will
163 result in ordinary ustar archives.
165 archive_write_set_compression_bzip2(),
166 archive_write_set_compression_compress(),
167 archive_write_set_compression_gzip(),
168 archive_write_set_compression_none()
169 The resulting archive will be compressed as specified. Note that
170 the compressed output is always properly blocked.
172 archive_write_set_compression_program()
173 The archive will be fed into the specified compression program.
174 The output of that program is blocked and written to the client
178 Freeze the settings, open the archive, and prepare for writing
179 entries. This is the most generic form of this function, which
180 accepts pointers to three callback functions which will be
181 invoked by the compression layer to write the constructed ar-
184 archive_write_open_fd()
185 A convenience form of archive_write_open() that accepts a file
186 descriptor. The archive_write_open_fd() function is safe for use
187 with tape drives or other block-oriented devices.
189 archive_write_open_FILE()
190 A convenience form of archive_write_open() that accepts a FILE *
191 pointer. Note that archive_write_open_FILE() is not safe for
192 writing to tape drives or other devices that require correct
195 archive_write_open_file()
196 A deprecated synonym for archive_write_open_filename().
198 archive_write_open_filename()
199 A convenience form of archive_write_open() that accepts a file-
200 name. A NULL argument indicates that the output should be writ-
201 ten to standard output; an argument of ``-'' will open a file
202 with that name. If you have not invoked
203 archive_write_set_bytes_in_last_block(), then
204 archive_write_open_filename() will adjust the last-block padding
205 depending on the file: it will enable padding when writing to
206 standard output or to a character or block device node, it will
207 disable padding otherwise. You can override this by manually
208 invoking archive_write_set_bytes_in_last_block() before calling
209 archive_write_open(). The archive_write_open_filename() function
210 is safe for use with tape drives or other block-oriented devices.
212 archive_write_open_memory()
213 A convenience form of archive_write_open() that accepts a pointer
214 to a block of memory that will receive the archive. The final
215 size_t * argument points to a variable that will be updated after
216 each write to reflect how much of the buffer is currently in use.
217 You should be careful to ensure that this variable remains allo-
218 cated until after the archive is closed.
220 archive_write_header()
221 Build and write a header using the data in the provided struct
222 archive_entry structure. See archive_entry(3) for information on
223 creating and populating struct archive_entry objects.
226 Write data corresponding to the header just written. Returns
227 number of bytes written or -1 on error.
229 archive_write_finish_entry()
230 Close out the entry just written. In particular, this writes out
231 the final padding required by some formats. Ordinarily, clients
232 never need to call this, as it is called automatically by
233 archive_write_next_header() and archive_write_close() as needed.
235 archive_write_close()
236 Complete the archive and invoke the close callback.
238 archive_write_finish()
239 Invokes archive_write_close() if it was not invoked manually,
240 then releases all resources. Note that this function was
241 declared to return void in libarchive 1.x, which made it impossi-
242 ble to detect errors when archive_write_close() was invoked
243 implicitly from this function. This is corrected beginning with
245 More information about the struct archive object and the overall design
246 of the library can be found in the libarchive(3) overview.
249 Compression support is built-in to libarchive, which uses zlib and bzlib
250 to handle gzip and bzip2 compression, respectively.
253 To use this library, you will need to define and register callback func-
254 tions that will be invoked to write data to the resulting archive. These
255 functions are registered by calling archive_write_open():
257 typedef int archive_open_callback(struct archive *, void
260 The open callback is invoked by archive_write_open(). It should return
261 ARCHIVE_OK if the underlying file or data source is successfully opened.
262 If the open fails, it should call archive_set_error() to register an
263 error code and message and return ARCHIVE_FATAL.
265 typedef ssize_t archive_write_callback(struct archive *,
266 void *client_data, void *buffer, size_t length)
268 The write callback is invoked whenever the library needs to write raw
269 bytes to the archive. For correct blocking, each call to the write call-
270 back function should translate into a single write(2) system call. This
271 is especially critical when writing archives to tape drives. On success,
272 the write callback should return the number of bytes actually written.
273 On error, the callback should invoke archive_set_error() to register an
274 error code and message and return -1.
276 typedef int archive_close_callback(struct archive *, void
279 The close callback is invoked by archive_close when the archive process-
280 ing is complete. The callback should return ARCHIVE_OK on success. On
281 failure, the callback should invoke archive_set_error() to register an
282 error code and message and return ARCHIVE_FATAL.
285 The following sketch illustrates basic usage of the library. In this
286 example, the callback functions are simply wrappers around the standard
287 open(2), write(2), and close(2) system calls.
289 #include <sys/stat.h>
291 #include <archive_entry.h>
302 myopen(struct archive *a, void *client_data)
304 struct mydata *mydata = client_data;
306 mydata->fd = open(mydata->name, O_WRONLY | O_CREAT, 0644);
310 return (ARCHIVE_FATAL);
314 mywrite(struct archive *a, void *client_data, void *buff, size_t n)
316 struct mydata *mydata = client_data;
318 return (write(mydata->fd, buff, n));
322 myclose(struct archive *a, void *client_data)
324 struct mydata *mydata = client_data;
332 write_archive(const char *outname, const char **filename)
334 struct mydata *mydata = malloc(sizeof(struct mydata));
336 struct archive_entry *entry;
342 a = archive_write_new();
343 mydata->name = outname;
344 archive_write_set_compression_gzip(a);
345 archive_write_set_format_ustar(a);
346 archive_write_open(a, mydata, myopen, mywrite, myclose);
348 stat(*filename, &st);
349 entry = archive_entry_new();
350 archive_entry_copy_stat(entry, &st);
351 archive_entry_set_pathname(entry, *filename);
352 archive_write_header(a, entry);
353 fd = open(*filename, O_RDONLY);
354 len = read(fd, buff, sizeof(buff));
356 archive_write_data(a, buff, len);
357 len = read(fd, buff, sizeof(buff));
359 archive_entry_free(entry);
362 archive_write_finish(a);
365 int main(int argc, const char **argv)
370 write_archive(outname, argv);
375 Most functions return ARCHIVE_OK (zero) on success, or one of several
376 non-zero error codes for errors. Specific error codes include:
377 ARCHIVE_RETRY for operations that might succeed if retried, ARCHIVE_WARN
378 for unusual conditions that do not prevent further operations, and
379 ARCHIVE_FATAL for serious errors that make remaining operations impossi-
380 ble. The archive_errno() and archive_error_string() functions can be
381 used to retrieve an appropriate error code and a textual error message.
383 archive_write_new() returns a pointer to a newly-allocated struct archive
386 archive_write_data() returns a count of the number of bytes actually
387 written. On error, -1 is returned and the archive_errno() and
388 archive_error_string() functions will return appropriate values. Note
389 that if the client-provided write callback function returns a non-zero
390 value, that error will be propagated back to the caller through whatever
391 API function resulted in that call, which may include
392 archive_write_header(), archive_write_data(), archive_write_close(), or
393 archive_write_finish(). The client callback can call archive_set_error()
394 to provide values that can then be retrieved by archive_errno() and
395 archive_error_string().
398 tar(1), libarchive(3), tar(5)
401 The libarchive library first appeared in FreeBSD 5.3.
404 The libarchive library was written by Tim Kientzle <kientzle@acm.org>.
407 There are many peculiar bugs in historic tar implementations that may
408 cause certain programs to reject archives written by this library. For
409 example, several historic implementations calculated header checksums
410 incorrectly and will thus reject valid archives; GNU tar does not fully
411 support pax interchange format; some old tar implementations required
412 specific field terminations.
414 The default pax interchange format eliminates most of the historic tar
415 limitations and provides a generic key/value attribute facility for ven-
416 dor-defined extensions. One oversight in POSIX is the failure to provide
417 a standard attribute for large device numbers. This library uses
418 ``SCHILY.devminor'' and ``SCHILY.devmajor'' for device numbers that
419 exceed the range supported by the backwards-compatible ustar header.
420 These keys are compatible with Joerg Schilling's star archiver. Other
421 implementations may not recognize these keys and will thus be unable to
422 correctly restore device nodes with large device numbers from archives
423 created by this library.
425 FreeBSD 6.0 May 11, 2008 FreeBSD 6.0