Lines Matching +full:k +full:- +full:block
3 bzip2, bunzip2 - a block-sorting file compressor, v1.0.6
4 bzcat - decompresses files to stdout
5 bzip2recover - recovers data from damaged bzip2 files
9 bzip2 [ -cdfkqstvzVL123456789 ] [ filenames ... ]
10 bunzip2 [ -fkvsVL ] [ filenames ... ]
11 bzcat [ -s ] [ filenames ... ]
16 bzip2 compresses files using the Burrows-Wheeler block
19 achieved by more conventional LZ77/LZ78-based compressors,
20 and approaches the performance of the PPM family of sta-
23 The command-line options are deliberately very similar to
26 bzip2 expects a list of file names to accompany the com-
27 mand-line flags. Each file is replaced by a compressed
29 Each compressed file has the same modification date, per-
30 missions, and, when possible, ownership as the correspond-
33 naive in the sense that there is no mechanism for preserv-
36 file name length restrictions, such as MS-DOS.
39 files. If you want this to happen, specify the -f flag.
47 bunzip2 (or bzip2 -d) decompresses all specified files.
64 As with compression, supplying no filenames causes decom-
67 bunzip2 will correctly decompress a file which is the con-
70 Integrity testing (-t) of concatenated compressed files is
74 output by giving the -c flag. Multiple files may be com-
77 files in this manner generates a stream containing multi-
80 later. Earlier versions of bzip2 will stop after decom-
83 bzcat (or bzip2 -dc) decompresses all specified files to
99 As a self-check for your protection, bzip2 uses 32-bit
101 is identical to the original. This guards against corrup-
118 -c --stdout
121 -d --decompress
128 -z --compress
129 The complement to -d: forces compression,
132 -t --test
137 -f --force
145 forced (-f), however, it will pass such files
148 -k --keep
152 -s --small
156 bytes per block byte. This means any file can be
157 decompressed in 2300k of memory, albeit at about
160 During compression, -s selects a block size of
161 200k, which limits memory use to around the same
164 megabytes or less), use -s for everything. See
167 -q --quiet
168 Suppress non-essential warning messages. Messages
172 -v --verbose
173 Verbose mode -- show the compression ratio for each
174 file processed. Further -v's increase the ver-
178 -L --license -V --version
182 -1 (or --fast) to -9 (or --best)
183 Set the block size to 100 k, 200 k .. 900 k when
185 See MEMORY MANAGEMENT below. The --fast and --best
187 In particular, --fast doesn't make things signifi-
188 cantly faster. And --best merely selects the
191 -- Treats all subsequent arguments as file names, even
192 if they start with a dash. This is so you can han-
194 example: bzip2 -- -myfilename.
196 --repetitive-fast --repetitive-best
199 behaviour of the sorting algorithm in earlier ver-
206 bzip2 compresses large files in blocks. The block size
209 The flags -1 through -9 specify the block size to be
210 100,000 bytes through 900,000 bytes (the default) respec-
211 tively. At decompression time, the block size used for
214 to decompress the file. Since block sizes are stored in
215 compressed files, it follows that the flags -1 to -9 are
221 Compression: 400k + ( 8 x block size )
223 Decompression: 100k + ( 4 x block size ), or
224 100k + ( 2.5 x block size )
226 Larger block sizes give rapidly diminishing marginal
228 or three hundred k of block size, a fact worth bearing in
232 block size.
234 For files compressed with the default 900k block size,
238 half this amount of memory, about 2300 kbytes. Decompres-
240 only where necessary. The relevant flag is -s.
242 In general, try and use the largest block size memory con-
244 achieved. Compression and decompression speed are virtu-
245 ally unaffected by block size.
248 single block -- that means most files you'd encounter
249 using a large block size. The amount of real memory
251 file is smaller than a block. For example, compressing a
252 file 20,000 bytes long with the flag -9 will cause the
253 compressor to allocate around 7600k of memory, but only
254 touch 400k + 20000 * 8 = 560 kbytes of it. Similarly, the
255 decompressor will allocate 3700k but only touch 100k +
259 for different block sizes. Also recorded is the total
260 compressed size for 14 files of the Calgary Text Compres-
262 some feel for how compression varies with block size.
264 block sizes for larger files, since the Corpus is domi-
268 Flag usage usage -s usage Size
270 -1 1200k 500k 350k 914704
271 -2 2000k 900k 600k 877703
272 -3 2800k 1300k 850k 860338
273 -4 3600k 1700k 1100k 846899
274 -5 4400k 2100k 1350k 845160
275 -6 5200k 2500k 1600k 838626
276 -7 6100k 2900k 1850k 834096
277 -8 6800k 3300k 2100k 828642
278 -9 7600k 3700k 2350k 828642
283 Each block is handled independently. If a media or trans-
284 mission error causes a multi-block .bz2 file to become
288 The compressed representation of each block is delimited
289 by a 48-bit pattern, which makes it possible to find the
290 block boundaries with reasonable certainty. Each block
291 also carries its own 32-bit CRC, so damaged blocks can be
295 search for blocks in .bz2 files, and write each block out
296 into its own .bz2 file. You can then use bzip2 -t to test
300 bzip2recover takes a single argument, the name of the dam-
304 designed so that the use of wildcards in subsequent pro-
305 cessing -- for example, "bzip2 -dc rec*file.bz2 > recov-
306 ered_data" -- processes the files in the correct order.
310 futile to use it on damaged single-block files, since a
311 damaged block cannot be recovered. If you wish to min-
312 imise any potential data loss through media or transmis-
314 block size.
324 between worst-case and average-case compression time is in
326 was more like 100:1. You can use the -vvvv option to mon-
332 operate in, and then charges all over it in a fairly ran-
333 dom fashion. This means that performance, both for com-
338 large performance improvements. I imagine bzip2 will per-
348 This manual page pertains to version 1.0.6 of bzip2. Com-
357 bzip2recover versions prior to 1.0.2 used 32-bit integers
360 long. Versions 1.0.2 and above use 64-bit ints on some
366 unsigned 64-bit integer.
374 The ideas embodied in bzip2 are due to (at least) the fol-
376 block sorting transformation), David Wheeler (again, for
377 the Huffman coder), Peter Fenwick (for the structured cod-
381 indebted for their help, support and advice. See the man-
384 for faster sorting algorithms, so as to speed up compres-
385 sion. Bela Lubkin encouraged me to improve the worst-case
386 compression performance. Donna Robinson XMLised the docu-