diff options
Diffstat (limited to 'bzip2.1.preformatted')
-rw-r--r-- | bzip2.1.preformatted | 440 |
1 files changed, 176 insertions, 264 deletions
diff --git a/bzip2.1.preformatted b/bzip2.1.preformatted index 8c4fab1..96b44be 100644 --- a/bzip2.1.preformatted +++ b/bzip2.1.preformatted | |||
@@ -1,24 +1,20 @@ | |||
1 | 1 | ||
2 | 2 | ||
3 | |||
4 | bzip2(1) bzip2(1) | ||
5 | |||
6 | |||
7 | NNAAMMEE | 3 | NNAAMMEE |
8 | bzip2, bunzip2 - a block-sorting file compressor, v0.9.0 | 4 | bzip2, bunzip2 - a block-sorting file compressor, v0.9.5 |
9 | bzcat - decompresses files to stdout | 5 | bzcat - decompresses files to stdout |
10 | bzip2recover - recovers data from damaged bzip2 files | 6 | bzip2recover - recovers data from damaged bzip2 files |
11 | 7 | ||
12 | 8 | ||
13 | SSYYNNOOPPSSIISS | 9 | SSYYNNOOPPSSIISS |
14 | bbzziipp22 [ --ccddffkkssttvvzzVVLL112233445566778899 ] [ _f_i_l_e_n_a_m_e_s _._._. ] | 10 | bbzziipp22 [ --ccddffkkqqssttvvzzVVLL112233445566778899 ] [ _f_i_l_e_n_a_m_e_s _._._. ] |
15 | bbuunnzziipp22 [ --ffkkvvssVVLL ] [ _f_i_l_e_n_a_m_e_s _._._. ] | 11 | bbuunnzziipp22 [ --ffkkvvssVVLL ] [ _f_i_l_e_n_a_m_e_s _._._. ] |
16 | bbzzccaatt [ --ss ] [ _f_i_l_e_n_a_m_e_s _._._. ] | 12 | bbzzccaatt [ --ss ] [ _f_i_l_e_n_a_m_e_s _._._. ] |
17 | bbzziipp22rreeccoovveerr _f_i_l_e_n_a_m_e | 13 | bbzziipp22rreeccoovveerr _f_i_l_e_n_a_m_e |
18 | 14 | ||
19 | 15 | ||
20 | DDEESSCCRRIIPPTTIIOONN | 16 | DDEESSCCRRIIPPTTIIOONN |
21 | _b_z_i_p_2 compresses files using the Burrows-Wheeler block- | 17 | _b_z_i_p_2 compresses files using the Burrows-Wheeler block |
22 | sorting text compression algorithm, and Huffman coding. | 18 | sorting text compression algorithm, and Huffman coding. |
23 | Compression is generally considerably better than that | 19 | Compression is generally considerably better than that |
24 | achieved by more conventional LZ77/LZ78-based compressors, | 20 | achieved by more conventional LZ77/LZ78-based compressors, |
@@ -26,22 +22,22 @@ DDEESSCCRRIIPPTTIIOONN | |||
26 | tistical compressors. | 22 | tistical compressors. |
27 | 23 | ||
28 | The command-line options are deliberately very similar to | 24 | The command-line options are deliberately very similar to |
29 | those of _G_N_U _G_z_i_p_, but they are not identical. | 25 | those of _G_N_U _g_z_i_p_, but they are not identical. |
30 | 26 | ||
31 | _b_z_i_p_2 expects a list of file names to accompany the com- | 27 | _b_z_i_p_2 expects a list of file names to accompany the com- |
32 | mand-line flags. Each file is replaced by a compressed | 28 | mand-line flags. Each file is replaced by a compressed |
33 | version of itself, with the name "original_name.bz2". | 29 | version of itself, with the name "original_name.bz2". |
34 | Each compressed file has the same modification date and | 30 | Each compressed file has the same modification date, per- |
35 | permissions as the corresponding original, so that these | 31 | missions, and, when possible, ownership as the correspond- |
36 | properties can be correctly restored at decompression | 32 | ing original, so that these properties can be correctly |
37 | time. File name handling is naive in the sense that there | 33 | restored at decompression time. File name handling is |
38 | is no mechanism for preserving original file names, per- | 34 | naive in the sense that there is no mechanism for preserv- |
39 | missions and dates in filesystems which lack these con- | 35 | ing original file names, permissions, ownerships or dates |
40 | cepts, or have serious file name length restrictions, such | 36 | in filesystems which lack these concepts, or have serious |
41 | as MS-DOS. | 37 | file name length restrictions, such as MS-DOS. |
42 | 38 | ||
43 | _b_z_i_p_2 and _b_u_n_z_i_p_2 will by default not overwrite existing | 39 | _b_z_i_p_2 and _b_u_n_z_i_p_2 will by default not overwrite existing |
44 | files; if you want this to happen, specify the -f flag. | 40 | files. If you want this to happen, specify the -f flag. |
45 | 41 | ||
46 | If no file names are specified, _b_z_i_p_2 compresses from | 42 | If no file names are specified, _b_z_i_p_2 compresses from |
47 | standard input to standard output. In this case, _b_z_i_p_2 | 43 | standard input to standard output. In this case, _b_z_i_p_2 |
@@ -49,42 +45,50 @@ DDEESSCCRRIIPPTTIIOONN | |||
49 | this would be entirely incomprehensible and therefore | 45 | this would be entirely incomprehensible and therefore |
50 | pointless. | 46 | pointless. |
51 | 47 | ||
52 | _b_u_n_z_i_p_2 (or _b_z_i_p_2 _-_d ) decompresses and restores all spec- | 48 | _b_u_n_z_i_p_2 (or _b_z_i_p_2 _-_d_) decompresses all specified files. |
53 | ified files whose names end in ".bz2". Files without this | 49 | Files which were not created by _b_z_i_p_2 will be detected and |
54 | suffix are ignored. Again, supplying no filenames causes | 50 | ignored, and a warning issued. _b_z_i_p_2 attempts to guess |
55 | decompression from standard input to standard output. | 51 | the filename for the decompressed file from that of the |
52 | compressed file as follows: | ||
53 | |||
54 | filename.bz2 becomes filename | ||
55 | filename.bz becomes filename | ||
56 | filename.tbz2 becomes filename.tar | ||
57 | filename.tbz becomes filename.tar | ||
58 | anyothername becomes anyothername.out | ||
59 | |||
60 | If the file does not end in one of the recognised endings, | ||
61 | _._b_z_2_, _._b_z_, _._t_b_z_2 or _._t_b_z_, _b_z_i_p_2 complains that it cannot | ||
62 | guess the name of the original file, and uses the original | ||
63 | name with _._o_u_t appended. | ||
64 | |||
65 | As with compression, supplying no filenames causes decom- | ||
66 | pression from standard input to standard output. | ||
56 | 67 | ||
57 | _b_u_n_z_i_p_2 will correctly decompress a file which is the con- | 68 | _b_u_n_z_i_p_2 will correctly decompress a file which is the con- |
58 | catenation of two or more compressed files. The result is | 69 | catenation of two or more compressed files. The result is |
59 | the concatenation of the corresponding uncompressed files. | 70 | the concatenation of the corresponding uncompressed files. |
60 | Integrity testing (-t) of concatenated compressed files is | 71 | Integrity testing (-t) of concatenated compressed files is |
61 | |||
62 | |||
63 | |||
64 | 1 | ||
65 | |||
66 | |||
67 | |||
68 | |||
69 | |||
70 | bzip2(1) bzip2(1) | ||
71 | |||
72 | |||
73 | also supported. | 72 | also supported. |
74 | 73 | ||
75 | You can also compress or decompress files to the standard | 74 | You can also compress or decompress files to the standard |
76 | output by giving the -c flag. Multiple files may be com- | 75 | output by giving the -c flag. Multiple files may be com- |
77 | pressed and decompressed like this. The resulting outputs | 76 | pressed and decompressed like this. The resulting outputs |
78 | are fed sequentially to stdout. Compression of multiple | 77 | are fed sequentially to stdout. Compression of multiple |
79 | files in this manner generates a stream containing multi- | 78 | files in this manner generates a stream containing multi- |
80 | ple compressed file representations. Such a stream can be | 79 | ple compressed file representations. Such a stream can be |
81 | decompressed correctly only by _b_z_i_p_2 version 0.9.0 or | 80 | decompressed correctly only by _b_z_i_p_2 version 0.9.0 or |
82 | later. Earlier versions of _b_z_i_p_2 will stop after decom- | 81 | later. Earlier versions of _b_z_i_p_2 will stop after decom- |
83 | pressing the first file in the stream. | 82 | pressing the first file in the stream. |
84 | 83 | ||
85 | _b_z_c_a_t (or _b_z_i_p_2 _-_d_c ) decompresses all specified files to | 84 | _b_z_c_a_t (or _b_z_i_p_2 _-_d_c_) decompresses all specified files to |
86 | the standard output. | 85 | the standard output. |
87 | 86 | ||
87 | _b_z_i_p_2 will read arguments from the environment variables | ||
88 | _B_Z_I_P_2 and _B_Z_I_P_, in that order, and will process them | ||
89 | before any arguments read from the command line. This | ||
90 | gives a convenient way to supply default arguments. | ||
91 | |||
88 | Compression is always performed, even if the compressed | 92 | Compression is always performed, even if the compressed |
89 | file is slightly larger than the original. Files of less | 93 | file is slightly larger than the original. Files of less |
90 | than about one hundred bytes tend to get larger, since the | 94 | than about one hundred bytes tend to get larger, since the |
@@ -101,121 +105,19 @@ bzip2(1) bzip2(1) | |||
101 | corruption going undetected is microscopic, about one | 105 | corruption going undetected is microscopic, about one |
102 | chance in four billion for each file processed. Be aware, | 106 | chance in four billion for each file processed. Be aware, |
103 | though, that the check occurs upon decompression, so it | 107 | though, that the check occurs upon decompression, so it |
104 | can only tell you that that something is wrong. It can't | 108 | can only tell you that something is wrong. It can't help |
105 | help you recover the original uncompressed data. You can | 109 | you recover the original uncompressed data. You can use |
106 | use _b_z_i_p_2_r_e_c_o_v_e_r to try to recover data from damaged | 110 | _b_z_i_p_2_r_e_c_o_v_e_r to try to recover data from damaged files. |
107 | files. | ||
108 | 111 | ||
109 | Return values: 0 for a normal exit, 1 for environmental | 112 | Return values: 0 for a normal exit, 1 for environmental |
110 | problems (file not found, invalid flags, I/O errors, &c), | 113 | problems (file not found, invalid flags, I/O errors, &c), |
111 | 2 to indicate a corrupt compressed file, 3 for an internal | 114 | 2 to indicate a corrupt compressed file, 3 for an internal |
112 | consistency error (eg, bug) which caused _b_z_i_p_2 to panic. | 115 | consistency error (eg, bug) which caused _b_z_i_p_2 to panic. |
113 | 116 | ||
114 | 117 | ||
115 | MMEEMMOORRYY MMAANNAAGGEEMMEENNTT | ||
116 | _B_z_i_p_2 compresses large files in blocks. The block size | ||
117 | affects both the compression ratio achieved, and the | ||
118 | amount of memory needed both for compression and decom- | ||
119 | pression. The flags -1 through -9 specify the block size | ||
120 | to be 100,000 bytes through 900,000 bytes (the default) | ||
121 | respectively. At decompression-time, the block size used | ||
122 | for compression is read from the header of the compressed | ||
123 | file, and _b_u_n_z_i_p_2 then allocates itself just enough memory | ||
124 | to decompress the file. Since block sizes are stored in | ||
125 | compressed files, it follows that the flags -1 to -9 are | ||
126 | irrelevant to and so ignored during decompression. | ||
127 | |||
128 | |||
129 | |||
130 | 2 | ||
131 | |||
132 | |||
133 | |||
134 | |||
135 | |||
136 | bzip2(1) bzip2(1) | ||
137 | |||
138 | |||
139 | Compression and decompression requirements, in bytes, can | ||
140 | be estimated as: | ||
141 | |||
142 | Compression: 400k + ( 7 x block size ) | ||
143 | |||
144 | Decompression: 100k + ( 4 x block size ), or | ||
145 | 100k + ( 2.5 x block size ) | ||
146 | |||
147 | Larger block sizes give rapidly diminishing marginal | ||
148 | returns; most of the compression comes from the first two | ||
149 | or three hundred k of block size, a fact worth bearing in | ||
150 | mind when using _b_z_i_p_2 on small machines. It is also | ||
151 | important to appreciate that the decompression memory | ||
152 | requirement is set at compression-time by the choice of | ||
153 | block size. | ||
154 | |||
155 | For files compressed with the default 900k block size, | ||
156 | _b_u_n_z_i_p_2 will require about 3700 kbytes to decompress. To | ||
157 | support decompression of any file on a 4 megabyte machine, | ||
158 | _b_u_n_z_i_p_2 has an option to decompress using approximately | ||
159 | half this amount of memory, about 2300 kbytes. Decompres- | ||
160 | sion speed is also halved, so you should use this option | ||
161 | only where necessary. The relevant flag is -s. | ||
162 | |||
163 | In general, try and use the largest block size memory con- | ||
164 | straints allow, since that maximises the compression | ||
165 | achieved. Compression and decompression speed are virtu- | ||
166 | ally unaffected by block size. | ||
167 | |||
168 | Another significant point applies to files which fit in a | ||
169 | single block -- that means most files you'd encounter | ||
170 | using a large block size. The amount of real memory | ||
171 | touched is proportional to the size of the file, since the | ||
172 | file is smaller than a block. For example, compressing a | ||
173 | file 20,000 bytes long with the flag -9 will cause the | ||
174 | compressor to allocate around 6700k of memory, but only | ||
175 | touch 400k + 20000 * 7 = 540 kbytes of it. Similarly, the | ||
176 | decompressor will allocate 3700k but only touch 100k + | ||
177 | 20000 * 4 = 180 kbytes. | ||
178 | |||
179 | Here is a table which summarises the maximum memory usage | ||
180 | for different block sizes. Also recorded is the total | ||
181 | compressed size for 14 files of the Calgary Text Compres- | ||
182 | sion Corpus totalling 3,141,622 bytes. This column gives | ||
183 | some feel for how compression varies with block size. | ||
184 | These figures tend to understate the advantage of larger | ||
185 | block sizes for larger files, since the Corpus is domi- | ||
186 | nated by smaller files. | ||
187 | |||
188 | Compress Decompress Decompress Corpus | ||
189 | Flag usage usage -s usage Size | ||
190 | |||
191 | -1 1100k 500k 350k 914704 | ||
192 | -2 1800k 900k 600k 877703 | ||
193 | |||
194 | |||
195 | |||
196 | 3 | ||
197 | |||
198 | |||
199 | |||
200 | |||
201 | |||
202 | bzip2(1) bzip2(1) | ||
203 | |||
204 | |||
205 | -3 2500k 1300k 850k 860338 | ||
206 | -4 3200k 1700k 1100k 846899 | ||
207 | -5 3900k 2100k 1350k 845160 | ||
208 | -6 4600k 2500k 1600k 838626 | ||
209 | -7 5400k 2900k 1850k 834096 | ||
210 | -8 6000k 3300k 2100k 828642 | ||
211 | -9 6700k 3700k 2350k 828642 | ||
212 | |||
213 | |||
214 | OOPPTTIIOONNSS | 118 | OOPPTTIIOONNSS |
215 | --cc ----ssttddoouutt | 119 | --cc ----ssttddoouutt |
216 | Compress or decompress to standard output. -c will | 120 | Compress or decompress to standard output. |
217 | decompress multiple files to stdout, but will only | ||
218 | compress a single file to stdout. | ||
219 | 121 | ||
220 | --dd ----ddeeccoommpprreessss | 122 | --dd ----ddeeccoommpprreessss |
221 | Force decompression. _b_z_i_p_2_, _b_u_n_z_i_p_2 and _b_z_c_a_t are | 123 | Force decompression. _b_z_i_p_2_, _b_u_n_z_i_p_2 and _b_z_c_a_t are |
@@ -235,7 +137,9 @@ OOPPTTIIOONNSS | |||
235 | 137 | ||
236 | --ff ----ffoorrccee | 138 | --ff ----ffoorrccee |
237 | Force overwrite of output files. Normally, _b_z_i_p_2 | 139 | Force overwrite of output files. Normally, _b_z_i_p_2 |
238 | will not overwrite existing output files. | 140 | will not overwrite existing output files. Also |
141 | forces _b_z_i_p_2 to break hard links to files, which it | ||
142 | otherwise wouldn't do. | ||
239 | 143 | ||
240 | --kk ----kkeeeepp | 144 | --kk ----kkeeeepp |
241 | Keep (don't delete) input files during compression | 145 | Keep (don't delete) input files during compression |
@@ -254,19 +158,12 @@ OOPPTTIIOONNSS | |||
254 | figure, at the expense of your compression ratio. | 158 | figure, at the expense of your compression ratio. |
255 | In short, if your machine is low on memory (8 | 159 | In short, if your machine is low on memory (8 |
256 | megabytes or less), use -s for everything. See | 160 | megabytes or less), use -s for everything. See |
257 | MEMORY MANAGEMENT above. | 161 | MEMORY MANAGEMENT below. |
258 | |||
259 | |||
260 | |||
261 | |||
262 | 4 | ||
263 | |||
264 | |||
265 | |||
266 | |||
267 | |||
268 | bzip2(1) bzip2(1) | ||
269 | 162 | ||
163 | --qq ----qquuiieett | ||
164 | Suppress non-essential warning messages. Messages | ||
165 | pertaining to I/O errors and other critical events | ||
166 | will not be suppressed. | ||
270 | 167 | ||
271 | --vv ----vveerrbboossee | 168 | --vv ----vveerrbboossee |
272 | Verbose mode -- show the compression ratio for each | 169 | Verbose mode -- show the compression ratio for each |
@@ -281,22 +178,96 @@ bzip2(1) bzip2(1) | |||
281 | --11 ttoo --99 | 178 | --11 ttoo --99 |
282 | Set the block size to 100 k, 200 k .. 900 k when | 179 | Set the block size to 100 k, 200 k .. 900 k when |
283 | compressing. Has no effect when decompressing. | 180 | compressing. Has no effect when decompressing. |
284 | See MEMORY MANAGEMENT above. | 181 | See MEMORY MANAGEMENT below. |
182 | |||
183 | ---- Treats all subsequent arguments as file names, even | ||
184 | if they start with a dash. This is so you can han- | ||
185 | dle files with names beginning with a dash, for | ||
186 | example: bzip2 -- -myfilename. | ||
187 | |||
188 | ----rreeppeettiittiivvee--ffaasstt ----rreeppeettiittiivvee--bbeesstt | ||
189 | These flags are redundant in versions 0.9.5 and | ||
190 | above. They provided some coarse control over the | ||
191 | behaviour of the sorting algorithm in earlier ver- | ||
192 | sions, which was sometimes useful. 0.9.5 and above | ||
193 | have an improved algorithm which renders these | ||
194 | flags irrelevant. | ||
195 | |||
196 | |||
197 | MMEEMMOORRYY MMAANNAAGGEEMMEENNTT | ||
198 | _b_z_i_p_2 compresses large files in blocks. The block size | ||
199 | affects both the compression ratio achieved, and the | ||
200 | amount of memory needed for compression and decompression. | ||
201 | The flags -1 through -9 specify the block size to be | ||
202 | 100,000 bytes through 900,000 bytes (the default) respec- | ||
203 | tively. At decompression time, the block size used for | ||
204 | compression is read from the header of the compressed | ||
205 | file, and _b_u_n_z_i_p_2 then allocates itself just enough memory | ||
206 | to decompress the file. Since block sizes are stored in | ||
207 | compressed files, it follows that the flags -1 to -9 are | ||
208 | irrelevant to and so ignored during decompression. | ||
285 | 209 | ||
286 | ----rreeppeettiittiivvee--ffaasstt | 210 | Compression and decompression requirements, in bytes, can |
287 | _b_z_i_p_2 injects some small pseudo-random variations | 211 | be estimated as: |
288 | into very repetitive blocks to limit worst-case | ||
289 | performance during compression. If sorting runs | ||
290 | into difficulties, the block is randomised, and | ||
291 | sorting is restarted. Very roughly, _b_z_i_p_2 persists | ||
292 | for three times as long as a well-behaved input | ||
293 | would take before resorting to randomisation. This | ||
294 | flag makes it give up much sooner. | ||
295 | 212 | ||
213 | Compression: 400k + ( 8 x block size ) | ||
296 | 214 | ||
297 | ----rreeppeettiittiivvee--bbeesstt | 215 | Decompression: 100k + ( 4 x block size ), or |
298 | Opposite of --repetitive-fast; try a lot harder | 216 | 100k + ( 2.5 x block size ) |
299 | before resorting to randomisation. | 217 | |
218 | Larger block sizes give rapidly diminishing marginal | ||
219 | returns. Most of the compression comes from the first two | ||
220 | or three hundred k of block size, a fact worth bearing in | ||
221 | mind when using _b_z_i_p_2 on small machines. It is also | ||
222 | important to appreciate that the decompression memory | ||
223 | requirement is set at compression time by the choice of | ||
224 | block size. | ||
225 | |||
226 | For files compressed with the default 900k block size, | ||
227 | _b_u_n_z_i_p_2 will require about 3700 kbytes to decompress. To | ||
228 | support decompression of any file on a 4 megabyte machine, | ||
229 | _b_u_n_z_i_p_2 has an option to decompress using approximately | ||
230 | half this amount of memory, about 2300 kbytes. Decompres- | ||
231 | sion speed is also halved, so you should use this option | ||
232 | only where necessary. The relevant flag is -s. | ||
233 | |||
234 | In general, try and use the largest block size memory con- | ||
235 | straints allow, since that maximises the compression | ||
236 | achieved. Compression and decompression speed are virtu- | ||
237 | ally unaffected by block size. | ||
238 | |||
239 | Another significant point applies to files which fit in a | ||
240 | single block -- that means most files you'd encounter | ||
241 | using a large block size. The amount of real memory | ||
242 | touched is proportional to the size of the file, since the | ||
243 | file is smaller than a block. For example, compressing a | ||
244 | file 20,000 bytes long with the flag -9 will cause the | ||
245 | compressor to allocate around 7600k of memory, but only | ||
246 | touch 400k + 20000 * 8 = 560 kbytes of it. Similarly, the | ||
247 | decompressor will allocate 3700k but only touch 100k + | ||
248 | 20000 * 4 = 180 kbytes. | ||
249 | |||
250 | Here is a table which summarises the maximum memory usage | ||
251 | for different block sizes. Also recorded is the total | ||
252 | compressed size for 14 files of the Calgary Text Compres- | ||
253 | sion Corpus totalling 3,141,622 bytes. This column gives | ||
254 | some feel for how compression varies with block size. | ||
255 | These figures tend to understate the advantage of larger | ||
256 | block sizes for larger files, since the Corpus is domi- | ||
257 | nated by smaller files. | ||
258 | |||
259 | Compress Decompress Decompress Corpus | ||
260 | Flag usage usage -s usage Size | ||
261 | |||
262 | -1 1200k 500k 350k 914704 | ||
263 | -2 2000k 900k 600k 877703 | ||
264 | -3 2800k 1300k 850k 860338 | ||
265 | -4 3600k 1700k 1100k 846899 | ||
266 | -5 4400k 2100k 1350k 845160 | ||
267 | -6 5200k 2500k 1600k 838626 | ||
268 | -7 6100k 2900k 1850k 834096 | ||
269 | -8 6800k 3300k 2100k 828642 | ||
270 | -9 7600k 3700k 2350k 828642 | ||
300 | 271 | ||
301 | 272 | ||
302 | RREECCOOVVEERRIINNGG DDAATTAA FFRROOMM DDAAMMAAGGEEDD FFIILLEESS | 273 | RREECCOOVVEERRIINNGG DDAATTAA FFRROOMM DDAAMMAAGGEEDD FFIILLEESS |
@@ -314,7 +285,7 @@ RREECCOOVVEERRIINNGG DDAATTAA FFRROOMM DDAAMMAAGGEEDD F | |||
314 | 285 | ||
315 | _b_z_i_p_2_r_e_c_o_v_e_r is a simple program whose purpose is to | 286 | _b_z_i_p_2_r_e_c_o_v_e_r is a simple program whose purpose is to |
316 | search for blocks in .bz2 files, and write each block out | 287 | search for blocks in .bz2 files, and write each block out |
317 | into its own .bz2 file. You can then use _b_z_i_p_2 _-_t to test | 288 | into its own .bz2 file. You can then use _b_z_i_p_2 -t to test |
318 | the integrity of the resulting files, and decompress those | 289 | the integrity of the resulting files, and decompress those |
319 | which are undamaged. | 290 | which are undamaged. |
320 | 291 | ||
@@ -322,21 +293,9 @@ RREECCOOVVEERRIINNGG DDAATTAA FFRROOMM DDAAMMAAGGEEDD F | |||
322 | aged file, and writes a number of files "rec0001file.bz2", | 293 | aged file, and writes a number of files "rec0001file.bz2", |
323 | "rec0002file.bz2", etc, containing the extracted blocks. | 294 | "rec0002file.bz2", etc, containing the extracted blocks. |
324 | The output filenames are designed so that the use of | 295 | The output filenames are designed so that the use of |
325 | |||
326 | |||
327 | |||
328 | 5 | ||
329 | |||
330 | |||
331 | |||
332 | |||
333 | |||
334 | bzip2(1) bzip2(1) | ||
335 | |||
336 | |||
337 | wildcards in subsequent processing -- for example, "bzip2 | 296 | wildcards in subsequent processing -- for example, "bzip2 |
338 | -dc rec*file.bz2 > recovered_data" -- lists the files in | 297 | -dc rec*file.bz2 > recovered_data" -- lists the files in |
339 | the "right" order. | 298 | the correct order. |
340 | 299 | ||
341 | _b_z_i_p_2_r_e_c_o_v_e_r should be of most use dealing with large .bz2 | 300 | _b_z_i_p_2_r_e_c_o_v_e_r should be of most use dealing with large .bz2 |
342 | files, as these will contain many blocks. It is clearly | 301 | files, as these will contain many blocks. It is clearly |
@@ -351,17 +310,15 @@ PPEERRFFOORRMMAANNCCEE NNOOTTEESS | |||
351 | The sorting phase of compression gathers together similar | 310 | The sorting phase of compression gathers together similar |
352 | strings in the file. Because of this, files containing | 311 | strings in the file. Because of this, files containing |
353 | very long runs of repeated symbols, like "aabaabaabaab | 312 | very long runs of repeated symbols, like "aabaabaabaab |
354 | ..." (repeated several hundred times) may compress | 313 | ..." (repeated several hundred times) may compress more |
355 | extraordinarily slowly. You can use the -vvvvv option to | 314 | slowly than normal. Versions 0.9.5 and above fare much |
356 | monitor progress in great detail, if you want. Decompres- | 315 | better than previous versions in this respect. The ratio |
357 | sion speed is unaffected. | 316 | between worst-case and average-case compression time is in |
358 | 317 | the region of 10:1. For previous versions, this figure | |
359 | Such pathological cases seem rare in practice, appearing | 318 | was more like 100:1. You can use the -vvvv option to mon- |
360 | mostly in artificially-constructed test files, and in low- | 319 | itor progress in great detail, if you want. |
361 | level disk images. It may be inadvisable to use _b_z_i_p_2 to | 320 | |
362 | compress the latter. If you do get a file which causes | 321 | Decompression speed is unaffected by these phenomena. |
363 | severe slowness in compression, try making the block size | ||
364 | as small as possible, with flag -1. | ||
365 | 322 | ||
366 | _b_z_i_p_2 usually allocates several megabytes of memory to | 323 | _b_z_i_p_2 usually allocates several megabytes of memory to |
367 | operate in, and then charges all over it in a fairly ran- | 324 | operate in, and then charges all over it in a fairly ran- |
@@ -376,88 +333,43 @@ PPEERRFFOORRMMAANNCCEE NNOOTTEESS | |||
376 | 333 | ||
377 | CCAAVVEEAATTSS | 334 | CCAAVVEEAATTSS |
378 | I/O error messages are not as helpful as they could be. | 335 | I/O error messages are not as helpful as they could be. |
379 | _B_z_i_p_2 tries hard to detect I/O errors and exit cleanly, | 336 | _b_z_i_p_2 tries hard to detect I/O errors and exit cleanly, |
380 | but the details of what the problem is sometimes seem | 337 | but the details of what the problem is sometimes seem |
381 | rather misleading. | 338 | rather misleading. |
382 | 339 | ||
383 | This manual page pertains to version 0.9.0 of _b_z_i_p_2_. Com- | 340 | This manual page pertains to version 0.9.5 of _b_z_i_p_2_. Com- |
384 | pressed data created by this version is entirely forwards | 341 | pressed data created by this version is entirely forwards |
385 | and backwards compatible with the previous public release, | 342 | and backwards compatible with the previous public |
386 | version 0.1pl2, but with the following exception: 0.9.0 | 343 | releases, versions 0.1pl2 and 0.9.0, but with the follow- |
387 | can correctly decompress multiple concatenated compressed | 344 | ing exception: 0.9.0 and above can correctly decompress |
388 | files. 0.1pl2 cannot do this; it will stop after decom- | 345 | multiple concatenated compressed files. 0.1pl2 cannot do |
389 | pressing just the first file in the stream. | 346 | this; it will stop after decompressing just the first file |
390 | 347 | in the stream. | |
391 | 348 | ||
392 | 349 | _b_z_i_p_2_r_e_c_o_v_e_r uses 32-bit integers to represent bit posi- | |
393 | 350 | tions in compressed files, so it cannot handle compressed | |
394 | 6 | 351 | files more than 512 megabytes long. This could easily be |
395 | |||
396 | |||
397 | |||
398 | |||
399 | |||
400 | bzip2(1) bzip2(1) | ||
401 | |||
402 | |||
403 | Wildcard expansion for Windows 95 and NT is flaky. | ||
404 | |||
405 | _b_z_i_p_2_r_e_c_o_v_e_r uses 32-bit integers to represent bit posi- | ||
406 | tions in compressed files, so it cannot handle compressed | ||
407 | files more than 512 megabytes long. This could easily be | ||
408 | fixed. | 352 | fixed. |
409 | 353 | ||
410 | 354 | ||
411 | AAUUTTHHOORR | 355 | AAUUTTHHOORR |
412 | Julian Seward, jseward@acm.org. | 356 | Julian Seward, jseward@acm.org. |
357 | |||
413 | http://www.muraroa.demon.co.uk | 358 | http://www.muraroa.demon.co.uk |
414 | 359 | ||
415 | The ideas embodied in _b_z_i_p_2 are due to (at least) the fol- | 360 | The ideas embodied in _b_z_i_p_2 are due to (at least) the fol- |
416 | lowing people: Michael Burrows and David Wheeler (for the | 361 | lowing people: Michael Burrows and David Wheeler (for the |
417 | block sorting transformation), David Wheeler (again, for | 362 | block sorting transformation), David Wheeler (again, for |
418 | the Huffman coder), Peter Fenwick (for the structured cod- | 363 | the Huffman coder), Peter Fenwick (for the structured cod- |
419 | ing model in the original _b_z_i_p_, and many refinements), and | 364 | ing model in the original _b_z_i_p_, and many refinements), and |
420 | Alistair Moffat, Radford Neal and Ian Witten (for the | 365 | Alistair Moffat, Radford Neal and Ian Witten (for the |
421 | arithmetic coder in the original _b_z_i_p_)_. I am much | 366 | arithmetic coder in the original _b_z_i_p_)_. I am much |
422 | indebted for their help, support and advice. See the man- | 367 | indebted for their help, support and advice. See the man- |
423 | ual in the source distribution for pointers to sources of | 368 | ual in the source distribution for pointers to sources of |
424 | documentation. Christian von Roques encouraged me to look | 369 | documentation. Christian von Roques encouraged me to look |
425 | for faster sorting algorithms, so as to speed up compres- | 370 | for faster sorting algorithms, so as to speed up compres- |
426 | sion. Bela Lubkin encouraged me to improve the worst-case | 371 | sion. Bela Lubkin encouraged me to improve the worst-case |
427 | compression performance. Many people sent patches, helped | 372 | compression performance. Many people sent patches, helped |
428 | with portability problems, lent machines, gave advice and | 373 | with portability problems, lent machines, gave advice and |
429 | were generally helpful. | 374 | were generally helpful. |
430 | 375 | ||
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