IO::Compress::Xz(3pm)

1IO::Compress::Xz(3)   User Contributed Perl Documentation  IO::Compress::Xz(3)
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NAME

6       IO::Compress::Xz - Write xz files/buffers
7

SYNOPSIS

9           use IO::Compress::Xz qw(xz $XzError) ;
10
11           my $status = xz $input => $output [,OPTS]
12               or die "xz failed: $XzError\n";
13
14           my $z = IO::Compress::Xz->new( $output [,OPTS] )
15               or die "xz failed: $XzError\n";
16
17           $z->print($string);
18           $z->printf($format, $string);
19           $z->write($string);
20           $z->syswrite($string [, $length, $offset]);
21           $z->flush();
22           $z->tell();
23           $z->eof();
24           $z->seek($position, $whence);
25           $z->binmode();
26           $z->fileno();
27           $z->opened();
28           $z->autoflush();
29           $z->input_line_number();
30           $z->newStream( [OPTS] );
31
32           $z->close() ;
33
34           $XzError ;
35
36           # IO::File mode
37
38           print $z $string;
39           printf $z $format, $string;
40           tell $z
41           eof $z
42           seek $z, $position, $whence
43           binmode $z
44           fileno $z
45           close $z ;
46

DESCRIPTION

48       This module provides a Perl interface that allows writing xz compressed
49       data to files or buffer.
50
51       For reading xz files/buffers, see the companion module
52       IO::Uncompress::UnXz.
53

Functional Interface

55       A top-level function, "xz", is provided to carry out "one-shot"
56       compression between buffers and/or files. For finer control over the
57       compression process, see the "OO Interface" section.
58
59           use IO::Compress::Xz qw(xz $XzError) ;
60
61           xz $input_filename_or_reference => $output_filename_or_reference [,OPTS]
62               or die "xz failed: $XzError\n";
63
64       The functional interface needs Perl5.005 or better.
65
66   xz $input_filename_or_reference => $output_filename_or_reference [, OPTS]
67       "xz" expects at least two parameters, $input_filename_or_reference and
68       $output_filename_or_reference and zero or more optional parameters (see
69       "Optional Parameters")
70
71       The $input_filename_or_reference parameter
72
73       The parameter, $input_filename_or_reference, is used to define the
74       source of the uncompressed data.
75
76       It can take one of the following forms:
77
78       A filename
79            If the $input_filename_or_reference parameter is a simple scalar,
80            it is assumed to be a filename. This file will be opened for
81            reading and the input data will be read from it.
82
83       A filehandle
84            If the $input_filename_or_reference parameter is a filehandle, the
85            input data will be read from it.  The string '-' can be used as an
86            alias for standard input.
87
88       A scalar reference
89            If $input_filename_or_reference is a scalar reference, the input
90            data will be read from $$input_filename_or_reference.
91
92       An array reference
93            If $input_filename_or_reference is an array reference, each
94            element in the array must be a filename.
95
96            The input data will be read from each file in turn.
97
98            The complete array will be walked to ensure that it only contains
99            valid filenames before any data is compressed.
100
101       An Input FileGlob string
102            If $input_filename_or_reference is a string that is delimited by
103            the characters "<" and ">" "xz" will assume that it is an input
104            fileglob string. The input is the list of files that match the
105            fileglob.
106
107            See File::GlobMapper for more details.
108
109       If the $input_filename_or_reference parameter is any other type,
110       "undef" will be returned.
111
112       The $output_filename_or_reference parameter
113
114       The parameter $output_filename_or_reference is used to control the
115       destination of the compressed data. This parameter can take one of
116       these forms.
117
118       A filename
119            If the $output_filename_or_reference parameter is a simple scalar,
120            it is assumed to be a filename.  This file will be opened for
121            writing and the compressed data will be written to it.
122
123       A filehandle
124            If the $output_filename_or_reference parameter is a filehandle,
125            the compressed data will be written to it.  The string '-' can be
126            used as an alias for standard output.
127
128       A scalar reference
129            If $output_filename_or_reference is a scalar reference, the
130            compressed data will be stored in $$output_filename_or_reference.
131
132       An Array Reference
133            If $output_filename_or_reference is an array reference, the
134            compressed data will be pushed onto the array.
135
136       An Output FileGlob
137            If $output_filename_or_reference is a string that is delimited by
138            the characters "<" and ">" "xz" will assume that it is an output
139            fileglob string. The output is the list of files that match the
140            fileglob.
141
142            When $output_filename_or_reference is an fileglob string,
143            $input_filename_or_reference must also be a fileglob string.
144            Anything else is an error.
145
146            See File::GlobMapper for more details.
147
148       If the $output_filename_or_reference parameter is any other type,
149       "undef" will be returned.
150
151   Notes
152       When $input_filename_or_reference maps to multiple files/buffers and
153       $output_filename_or_reference is a single file/buffer the input
154       files/buffers will be stored in $output_filename_or_reference as a
155       concatenated series of compressed data streams.
156
157   Optional Parameters
158       The optional parameters for the one-shot function "xz" are (for the
159       most part) identical to those used with the OO interface defined in the
160       "Constructor Options" section. The exceptions are listed below
161
162       "AutoClose => 0|1"
163            This option applies to any input or output data streams to "xz"
164            that are filehandles.
165
166            If "AutoClose" is specified, and the value is true, it will result
167            in all input and/or output filehandles being closed once "xz" has
168            completed.
169
170            This parameter defaults to 0.
171
172       "BinModeIn => 0|1"
173            This option is now a no-op. All files will be read in binmode.
174
175       "Append => 0|1"
176            The behaviour of this option is dependent on the type of output
177            data stream.
178
179            •    A Buffer
180
181                 If "Append" is enabled, all compressed data will be append to
182                 the end of the output buffer. Otherwise the output buffer
183                 will be cleared before any compressed data is written to it.
184
185            •    A Filename
186
187                 If "Append" is enabled, the file will be opened in append
188                 mode. Otherwise the contents of the file, if any, will be
189                 truncated before any compressed data is written to it.
190
191            •    A Filehandle
192
193                 If "Append" is enabled, the filehandle will be positioned to
194                 the end of the file via a call to "seek" before any
195                 compressed data is written to it.  Otherwise the file pointer
196                 will not be moved.
197
198            When "Append" is specified, and set to true, it will append all
199            compressed data to the output data stream.
200
201            So when the output is a filehandle it will carry out a seek to the
202            eof before writing any compressed data. If the output is a
203            filename, it will be opened for appending. If the output is a
204            buffer, all compressed data will be appended to the existing
205            buffer.
206
207            Conversely when "Append" is not specified, or it is present and is
208            set to false, it will operate as follows.
209
210            When the output is a filename, it will truncate the contents of
211            the file before writing any compressed data. If the output is a
212            filehandle its position will not be changed. If the output is a
213            buffer, it will be wiped before any compressed data is output.
214
215            Defaults to 0.
216
217   Examples
218       Here are a few example that show the capabilities of the module.
219
220       Streaming
221
222       This very simple command line example demonstrates the streaming
223       capabilities of the module.  The code reads data from STDIN, compresses
224       it, and writes the compressed data to STDOUT.
225
226           $ echo hello world | perl -MIO::Compress::Xz=xz -e 'xz \*STDIN => \*STDOUT' >output.xz
227
228       The special filename "-" can be used as a standin for both "\*STDIN"
229       and "\*STDOUT", so the above can be rewritten as
230
231           $ echo hello world | perl -MIO::Compress::Xz=xz -e 'xz "-" => "-"' >output.xz
232
233       Compressing a file from the filesystem
234
235       To read the contents of the file "file1.txt" and write the compressed
236       data to the file "file1.txt.xz".
237
238           use strict ;
239           use warnings ;
240           use IO::Compress::Xz qw(xz $XzError) ;
241
242           my $input = "file1.txt";
243           xz $input => "$input.xz"
244               or die "xz failed: $XzError\n";
245
246       Reading from a Filehandle and writing to an in-memory buffer
247
248       To read from an existing Perl filehandle, $input, and write the
249       compressed data to a buffer, $buffer.
250
251           use strict ;
252           use warnings ;
253           use IO::Compress::Xz qw(xz $XzError) ;
254           use IO::File ;
255
256           my $input = IO::File->new( "<file1.txt" )
257               or die "Cannot open 'file1.txt': $!\n" ;
258           my $buffer ;
259           xz $input => \$buffer
260               or die "xz failed: $XzError\n";
261
262       Compressing multiple files
263
264       To compress all files in the directory "/my/home" that match "*.txt"
265       and store the compressed data in the same directory
266
267           use strict ;
268           use warnings ;
269           use IO::Compress::Xz qw(xz $XzError) ;
270
271           xz '</my/home/*.txt>' => '<*.xz>'
272               or die "xz failed: $XzError\n";
273
274       and if you want to compress each file one at a time, this will do the
275       trick
276
277           use strict ;
278           use warnings ;
279           use IO::Compress::Xz qw(xz $XzError) ;
280
281           for my $input ( glob "/my/home/*.txt" )
282           {
283               my $output = "$input.xz" ;
284               xz $input => $output
285                   or die "Error compressing '$input': $XzError\n";
286           }
287

OO Interface

289   Constructor
290       The format of the constructor for "IO::Compress::Xz" is shown below
291
292           my $z = IO::Compress::Xz->new( $output [,OPTS] )
293               or die "IO::Compress::Xz failed: $XzError\n";
294
295       It returns an "IO::Compress::Xz" object on success and undef on
296       failure.  The variable $XzError will contain an error message on
297       failure.
298
299       If you are running Perl 5.005 or better the object, $z, returned from
300       IO::Compress::Xz can be used exactly like an IO::File filehandle.  This
301       means that all normal output file operations can be carried out with
302       $z.  For example, to write to a compressed file/buffer you can use
303       either of these forms
304
305           $z->print("hello world\n");
306           print $z "hello world\n";
307
308       The mandatory parameter $output is used to control the destination of
309       the compressed data. This parameter can take one of these forms.
310
311       A filename
312            If the $output parameter is a simple scalar, it is assumed to be a
313            filename. This file will be opened for writing and the compressed
314            data will be written to it.
315
316       A filehandle
317            If the $output parameter is a filehandle, the compressed data will
318            be written to it.  The string '-' can be used as an alias for
319            standard output.
320
321       A scalar reference
322            If $output is a scalar reference, the compressed data will be
323            stored in $$output.
324
325       If the $output parameter is any other type, "IO::Compress::Xz"::new
326       will return undef.
327
328   Constructor Options
329       "OPTS" is any combination of zero or more the following options:
330
331       "AutoClose => 0|1"
332            This option is only valid when the $output parameter is a
333            filehandle. If specified, and the value is true, it will result in
334            the $output being closed once either the "close" method is called
335            or the "IO::Compress::Xz" object is destroyed.
336
337            This parameter defaults to 0.
338
339       "Append => 0|1"
340            Opens $output in append mode.
341
342            The behaviour of this option is dependent on the type of $output.
343
344            •    A Buffer
345
346                 If $output is a buffer and "Append" is enabled, all
347                 compressed data will be append to the end of $output.
348                 Otherwise $output will be cleared before any data is written
349                 to it.
350
351            •    A Filename
352
353                 If $output is a filename and "Append" is enabled, the file
354                 will be opened in append mode. Otherwise the contents of the
355                 file, if any, will be truncated before any compressed data is
356                 written to it.
357
358            •    A Filehandle
359
360                 If $output is a filehandle, the file pointer will be
361                 positioned to the end of the file via a call to "seek" before
362                 any compressed data is written to it.  Otherwise the file
363                 pointer will not be moved.
364
365            This parameter defaults to 0.
366
367       "Preset => $preset"
368            Used to choose the compression preset.
369
370            Valid values are 0-9 and "LZMA_PRESET_DEFAULT".
371
372            0 is the fastest compression with the lowest memory usage and the
373            lowest compression.
374
375            9 is the slowest compression with the highest memory usage but
376            with the best compression.
377
378            Defaults to "LZMA_PRESET_DEFAULT" (6).
379
380       "Extreme => 0|1"
381            Makes the compression a lot slower, but a small compression gain.
382
383            Defaults to 0.
384
385       "Check => $check"
386            Used to specify the integrrity check used in the xz data stream.
387            Valid values are "LZMA_CHECK_NONE", "LZMA_CHECK_CRC32",
388            "LZMA_CHECK_CRC64", "LZMA_CHECK_SHA256".
389
390            Defaults to "LZMA_CHECK_CRC32".
391
392       "Strict => 0|1"
393            This is a placeholder option.
394
395   Examples
396       TODO
397

Methods

399   print
400       Usage is
401
402           $z->print($data)
403           print $z $data
404
405       Compresses and outputs the contents of the $data parameter. This has
406       the same behaviour as the "print" built-in.
407
408       Returns true if successful.
409
410   printf
411       Usage is
412
413           $z->printf($format, $data)
414           printf $z $format, $data
415
416       Compresses and outputs the contents of the $data parameter.
417
418       Returns true if successful.
419
420   syswrite
421       Usage is
422
423           $z->syswrite $data
424           $z->syswrite $data, $length
425           $z->syswrite $data, $length, $offset
426
427       Compresses and outputs the contents of the $data parameter.
428
429       Returns the number of uncompressed bytes written, or "undef" if
430       unsuccessful.
431
432   write
433       Usage is
434
435           $z->write $data
436           $z->write $data, $length
437           $z->write $data, $length, $offset
438
439       Compresses and outputs the contents of the $data parameter.
440
441       Returns the number of uncompressed bytes written, or "undef" if
442       unsuccessful.
443
444   flush
445       Usage is
446
447           $z->flush;
448
449       Flushes any pending compressed data to the output file/buffer.
450
451       Returns true on success.
452
453   tell
454       Usage is
455
456           $z->tell()
457           tell $z
458
459       Returns the uncompressed file offset.
460
461   eof
462       Usage is
463
464           $z->eof();
465           eof($z);
466
467       Returns true if the "close" method has been called.
468
469   seek
470           $z->seek($position, $whence);
471           seek($z, $position, $whence);
472
473       Provides a sub-set of the "seek" functionality, with the restriction
474       that it is only legal to seek forward in the output file/buffer.  It is
475       a fatal error to attempt to seek backward.
476
477       Empty parts of the file/buffer will have NULL (0x00) bytes written to
478       them.
479
480       The $whence parameter takes one the usual values, namely SEEK_SET,
481       SEEK_CUR or SEEK_END.
482
483       Returns 1 on success, 0 on failure.
484
485   binmode
486       Usage is
487
488           $z->binmode
489           binmode $z ;
490
491       This is a noop provided for completeness.
492
493   opened
494           $z->opened()
495
496       Returns true if the object currently refers to a opened file/buffer.
497
498   autoflush
499           my $prev = $z->autoflush()
500           my $prev = $z->autoflush(EXPR)
501
502       If the $z object is associated with a file or a filehandle, this method
503       returns the current autoflush setting for the underlying filehandle. If
504       "EXPR" is present, and is non-zero, it will enable flushing after every
505       write/print operation.
506
507       If $z is associated with a buffer, this method has no effect and always
508       returns "undef".
509
510       Note that the special variable $| cannot be used to set or retrieve the
511       autoflush setting.
512
513   input_line_number
514           $z->input_line_number()
515           $z->input_line_number(EXPR)
516
517       This method always returns "undef" when compressing.
518
519   fileno
520           $z->fileno()
521           fileno($z)
522
523       If the $z object is associated with a file or a filehandle, "fileno"
524       will return the underlying file descriptor. Once the "close" method is
525       called "fileno" will return "undef".
526
527       If the $z object is associated with a buffer, this method will return
528       "undef".
529
530   close
531           $z->close() ;
532           close $z ;
533
534       Flushes any pending compressed data and then closes the output
535       file/buffer.
536
537       For most versions of Perl this method will be automatically invoked if
538       the IO::Compress::Xz object is destroyed (either explicitly or by the
539       variable with the reference to the object going out of scope). The
540       exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In these
541       cases, the "close" method will be called automatically, but not until
542       global destruction of all live objects when the program is terminating.
543
544       Therefore, if you want your scripts to be able to run on all versions
545       of Perl, you should call "close" explicitly and not rely on automatic
546       closing.
547
548       Returns true on success, otherwise 0.
549
550       If the "AutoClose" option has been enabled when the IO::Compress::Xz
551       object was created, and the object is associated with a file, the
552       underlying file will also be closed.
553
554   newStream([OPTS])
555       Usage is
556
557           $z->newStream( [OPTS] )
558
559       Closes the current compressed data stream and starts a new one.
560
561       OPTS consists of any of the options that are available when creating
562       the $z object.
563
564       See the "Constructor Options" section for more details.
565

Importing

567       No symbolic constants are required by IO::Compress::Xz at present.
568
569       :all Imports "xz" and $XzError.  Same as doing this
570
571                use IO::Compress::Xz qw(xz $XzError) ;
572

EXAMPLES

SUPPORT

575       General feedback/questions/bug reports should be sent to
576       <https://github.com/pmqs/IO-Compress-Lzma/issues> (preferred) or
577       <https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress-Lzma>.
578

AUTHOR

595       This module was written by Paul Marquess, "pmqs@cpan.org".
596

MODIFICATION HISTORY

598       See the Changes file.
599

COPYRIGHT AND LICENSE

601       Copyright (c) 2005-2021 Paul Marquess. All rights reserved.
602
603       This program is free software; you can redistribute it and/or modify it
604       under the same terms as Perl itself.
605
606
607
608perl v5.34.0                      2021-07-22               IO::Compress::Xz(3)