IO::Uncompress::UnXz(3pm)

1IO::Uncompress::UnXz(3)User Contributed Perl DocumentatioInO::Uncompress::UnXz(3)
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NAME

6       IO::Uncompress::UnXz - Read xz files/buffers
7

SYNOPSIS

9           use IO::Uncompress::UnXz qw(unxz $UnXzError) ;
10
11           my $status = unxz $input => $output [,OPTS]
12               or die "unxz failed: $UnXzError\n";
13
14           my $z = IO::Uncompress::UnXz->new( $input [OPTS] )
15               or die "unxz failed: $UnXzError\n";
16
17           $status = $z->read($buffer)
18           $status = $z->read($buffer, $length)
19           $status = $z->read($buffer, $length, $offset)
20           $line = $z->getline()
21           $char = $z->getc()
22           $char = $z->ungetc()
23           $char = $z->opened()
24
25           $data = $z->trailingData()
26           $status = $z->nextStream()
27           $data = $z->getHeaderInfo()
28           $z->tell()
29           $z->seek($position, $whence)
30           $z->binmode()
31           $z->fileno()
32           $z->eof()
33           $z->close()
34
35           $UnXzError ;
36
37           # IO::File mode
38
39           <$z>
40           read($z, $buffer);
41           read($z, $buffer, $length);
42           read($z, $buffer, $length, $offset);
43           tell($z)
44           seek($z, $position, $whence)
45           binmode($z)
46           fileno($z)
47           eof($z)
48           close($z)
49

DESCRIPTION

51       This module provides a Perl interface that allows the reading of lzma
52       files/buffers.
53
54       For writing xz files/buffers, see the companion module
55       IO::Compress::Xz.
56

Functional Interface

58       A top-level function, "unxz", is provided to carry out "one-shot"
59       uncompression between buffers and/or files. For finer control over the
60       uncompression process, see the "OO Interface" section.
61
62           use IO::Uncompress::UnXz qw(unxz $UnXzError) ;
63
64           unxz $input_filename_or_reference => $output_filename_or_reference [,OPTS]
65               or die "unxz failed: $UnXzError\n";
66
67       The functional interface needs Perl5.005 or better.
68
69   unxz $input_filename_or_reference => $output_filename_or_reference [, OPTS]
70       "unxz" expects at least two parameters, $input_filename_or_reference
71       and $output_filename_or_reference and zero or more optional parameters
72       (see "Optional Parameters")
73
74       The $input_filename_or_reference parameter
75
76       The parameter, $input_filename_or_reference, is used to define the
77       source of the compressed data.
78
79       It can take one of the following forms:
80
81       A filename
82            If the $input_filename_or_reference parameter is a simple scalar,
83            it is assumed to be a filename. This file will be opened for
84            reading and the input data will be read from it.
85
86       A filehandle
87            If the $input_filename_or_reference parameter is a filehandle, the
88            input data will be read from it.  The string '-' can be used as an
89            alias for standard input.
90
91       A scalar reference
92            If $input_filename_or_reference is a scalar reference, the input
93            data will be read from $$input_filename_or_reference.
94
95       An array reference
96            If $input_filename_or_reference is an array reference, each
97            element in the array must be a filename.
98
99            The input data will be read from each file in turn.
100
101            The complete array will be walked to ensure that it only contains
102            valid filenames before any data is uncompressed.
103
104       An Input FileGlob string
105            If $input_filename_or_reference is a string that is delimited by
106            the characters "<" and ">" "unxz" will assume that it is an input
107            fileglob string. The input is the list of files that match the
108            fileglob.
109
110            See File::GlobMapper for more details.
111
112       If the $input_filename_or_reference parameter is any other type,
113       "undef" will be returned.
114
115       The $output_filename_or_reference parameter
116
117       The parameter $output_filename_or_reference is used to control the
118       destination of the uncompressed data. This parameter can take one of
119       these forms.
120
121       A filename
122            If the $output_filename_or_reference parameter is a simple scalar,
123            it is assumed to be a filename.  This file will be opened for
124            writing and the uncompressed data will be written to it.
125
126       A filehandle
127            If the $output_filename_or_reference parameter is a filehandle,
128            the uncompressed data will be written to it.  The string '-' can
129            be used as an alias for standard output.
130
131       A scalar reference
132            If $output_filename_or_reference is a scalar reference, the
133            uncompressed data will be stored in
134            $$output_filename_or_reference.
135
136       An Array Reference
137            If $output_filename_or_reference is an array reference, the
138            uncompressed data will be pushed onto the array.
139
140       An Output FileGlob
141            If $output_filename_or_reference is a string that is delimited by
142            the characters "<" and ">" "unxz" will assume that it is an output
143            fileglob string. The output is the list of files that match the
144            fileglob.
145
146            When $output_filename_or_reference is an fileglob string,
147            $input_filename_or_reference must also be a fileglob string.
148            Anything else is an error.
149
150            See File::GlobMapper for more details.
151
152       If the $output_filename_or_reference parameter is any other type,
153       "undef" will be returned.
154
155   Notes
156       When $input_filename_or_reference maps to multiple compressed
157       files/buffers and $output_filename_or_reference is a single
158       file/buffer, after uncompression $output_filename_or_reference will
159       contain a concatenation of all the uncompressed data from each of the
160       input files/buffers.
161
162   Optional Parameters
163       The optional parameters for the one-shot function "unxz" are (for the
164       most part) identical to those used with the OO interface defined in the
165       "Constructor Options" section. The exceptions are listed below
166
167       "AutoClose => 0|1"
168            This option applies to any input or output data streams to "unxz"
169            that are filehandles.
170
171            If "AutoClose" is specified, and the value is true, it will result
172            in all input and/or output filehandles being closed once "unxz"
173            has completed.
174
175            This parameter defaults to 0.
176
177       "BinModeOut => 0|1"
178            This option is now a no-op. All files will be written  in binmode.
179
180       "Append => 0|1"
181            The behaviour of this option is dependent on the type of output
182            data stream.
183
184            •    A Buffer
185
186                 If "Append" is enabled, all uncompressed data will be append
187                 to the end of the output buffer. Otherwise the output buffer
188                 will be cleared before any uncompressed data is written to
189                 it.
190
191            •    A Filename
192
193                 If "Append" is enabled, the file will be opened in append
194                 mode. Otherwise the contents of the file, if any, will be
195                 truncated before any uncompressed data is written to it.
196
197            •    A Filehandle
198
199                 If "Append" is enabled, the filehandle will be positioned to
200                 the end of the file via a call to "seek" before any
201                 uncompressed data is written to it.  Otherwise the file
202                 pointer will not be moved.
203
204            When "Append" is specified, and set to true, it will append all
205            uncompressed data to the output data stream.
206
207            So when the output is a filehandle it will carry out a seek to the
208            eof before writing any uncompressed data. If the output is a
209            filename, it will be opened for appending. If the output is a
210            buffer, all uncompressed data will be appended to the existing
211            buffer.
212
213            Conversely when "Append" is not specified, or it is present and is
214            set to false, it will operate as follows.
215
216            When the output is a filename, it will truncate the contents of
217            the file before writing any uncompressed data. If the output is a
218            filehandle its position will not be changed. If the output is a
219            buffer, it will be wiped before any uncompressed data is output.
220
221            Defaults to 0.
222
223       "MultiStream => 0|1"
224            If the input file/buffer contains multiple compressed data
225            streams, this option will uncompress the whole lot as a single
226            data stream.
227
228            Defaults to 0.
229
230       "TrailingData => $scalar"
231            Returns the data, if any, that is present immediately after the
232            compressed data stream once uncompression is complete.
233
234            This option can be used when there is useful information
235            immediately following the compressed data stream, and you don't
236            know the length of the compressed data stream.
237
238            If the input is a buffer, "trailingData" will return everything
239            from the end of the compressed data stream to the end of the
240            buffer.
241
242            If the input is a filehandle, "trailingData" will return the data
243            that is left in the filehandle input buffer once the end of the
244            compressed data stream has been reached. You can then use the
245            filehandle to read the rest of the input file.
246
247            Don't bother using "trailingData" if the input is a filename.
248
249            If you know the length of the compressed data stream before you
250            start uncompressing, you can avoid having to use "trailingData" by
251            setting the "InputLength" option.
252
253   Examples
254       To read the contents of the file "file1.txt.xz" and write the
255       uncompressed data to the file "file1.txt".
256
257           use strict ;
258           use warnings ;
259           use IO::Uncompress::UnXz qw(unxz $UnXzError) ;
260
261           my $input = "file1.txt.xz";
262           my $output = "file1.txt";
263           unxz $input => $output
264               or die "unxz failed: $UnXzError\n";
265
266       To read from an existing Perl filehandle, $input, and write the
267       uncompressed data to a buffer, $buffer.
268
269           use strict ;
270           use warnings ;
271           use IO::Uncompress::UnXz qw(unxz $UnXzError) ;
272           use IO::File ;
273
274           my $input = IO::File->new( "<file1.txt.xz" )
275               or die "Cannot open 'file1.txt.xz': $!\n" ;
276           my $buffer ;
277           unxz $input => \$buffer
278               or die "unxz failed: $UnXzError\n";
279
280       To uncompress all files in the directory "/my/home" that match
281       "*.txt.xz" and store the compressed data in the same directory
282
283           use strict ;
284           use warnings ;
285           use IO::Uncompress::UnXz qw(unxz $UnXzError) ;
286
287           unxz '</my/home/*.txt.xz>' => '</my/home/#1.txt>'
288               or die "unxz failed: $UnXzError\n";
289
290       and if you want to compress each file one at a time, this will do the
291       trick
292
293           use strict ;
294           use warnings ;
295           use IO::Uncompress::UnXz qw(unxz $UnXzError) ;
296
297           for my $input ( glob "/my/home/*.txt.xz" )
298           {
299               my $output = $input;
300               $output =~ s/.xz// ;
301               unxz $input => $output
302                   or die "Error compressing '$input': $UnXzError\n";
303           }
304

OO Interface

306   Constructor
307       The format of the constructor for IO::Uncompress::UnXz is shown below
308
309           my $z = IO::Uncompress::UnXz->new( $input [OPTS] )
310               or die "IO::Uncompress::UnXz failed: $UnXzError\n";
311
312       Returns an "IO::Uncompress::UnXz" object on success and undef on
313       failure.  The variable $UnXzError will contain an error message on
314       failure.
315
316       If you are running Perl 5.005 or better the object, $z, returned from
317       IO::Uncompress::UnXz can be used exactly like an IO::File filehandle.
318       This means that all normal input file operations can be carried out
319       with $z.  For example, to read a line from a compressed file/buffer you
320       can use either of these forms
321
322           $line = $z->getline();
323           $line = <$z>;
324
325       The mandatory parameter $input is used to determine the source of the
326       compressed data. This parameter can take one of three forms.
327
328       A filename
329            If the $input parameter is a scalar, it is assumed to be a
330            filename. This file will be opened for reading and the compressed
331            data will be read from it.
332
333       A filehandle
334            If the $input parameter is a filehandle, the compressed data will
335            be read from it.  The string '-' can be used as an alias for
336            standard input.
337
338       A scalar reference
339            If $input is a scalar reference, the compressed data will be read
340            from $$input.
341
342   Constructor Options
343       The option names defined below are case insensitive and can be
344       optionally prefixed by a '-'.  So all of the following are valid
345
346           -AutoClose
347           -autoclose
348           AUTOCLOSE
349           autoclose
350
351       OPTS is a combination of the following options:
352
353       "AutoClose => 0|1"
354            This option is only valid when the $input parameter is a
355            filehandle. If specified, and the value is true, it will result in
356            the file being closed once either the "close" method is called or
357            the IO::Uncompress::UnXz object is destroyed.
358
359            This parameter defaults to 0.
360
361       "MultiStream => 0|1"
362            Allows multiple concatenated compressed streams to be treated as a
363            single compressed stream. Decompression will stop once either the
364            end of the file/buffer is reached, an error is encountered
365            (premature eof, corrupt compressed data) or the end of a stream is
366            not immediately followed by the start of another stream.
367
368            This parameter defaults to 0.
369
370       "Prime => $string"
371            This option will uncompress the contents of $string before
372            processing the input file/buffer.
373
374            This option can be useful when the compressed data is embedded in
375            another file/data structure and it is not possible to work out
376            where the compressed data begins without having to read the first
377            few bytes. If this is the case, the uncompression can be primed
378            with these bytes using this option.
379
380       "Transparent => 0|1"
381            If this option is set and the input file/buffer is not compressed
382            data, the module will allow reading of it anyway.
383
384            In addition, if the input file/buffer does contain compressed data
385            and there is non-compressed data immediately following it, setting
386            this option will make this module treat the whole file/buffer as a
387            single data stream.
388
389            This option defaults to 1.
390
391       "BlockSize => $num"
392            When reading the compressed input data, IO::Uncompress::UnXz will
393            read it in blocks of $num bytes.
394
395            This option defaults to 4096.
396
397       "InputLength => $size"
398            When present this option will limit the number of compressed bytes
399            read from the input file/buffer to $size. This option can be used
400            in the situation where there is useful data directly after the
401            compressed data stream and you know beforehand the exact length of
402            the compressed data stream.
403
404            This option is mostly used when reading from a filehandle, in
405            which case the file pointer will be left pointing to the first
406            byte directly after the compressed data stream.
407
408            This option defaults to off.
409
410       "Append => 0|1"
411            This option controls what the "read" method does with uncompressed
412            data.
413
414            If set to 1, all uncompressed data will be appended to the output
415            parameter of the "read" method.
416
417            If set to 0, the contents of the output parameter of the "read"
418            method will be overwritten by the uncompressed data.
419
420            Defaults to 0.
421
422       "Strict => 0|1"
423            This option controls whether the extra checks defined below are
424            used when carrying out the decompression. When Strict is on, the
425            extra tests are carried out, when Strict is off they are not.
426
427            The default for this option is off.
428
429       "MemLimit => $number"
430            Default is 128Meg.
431
432       "Flags => $flags"
433            Default is 0.
434
435   Examples
436       TODO
437

Methods

439   read
440       Usage is
441
442           $status = $z->read($buffer)
443
444       Reads a block of compressed data (the size of the compressed block is
445       determined by the "Buffer" option in the constructor), uncompresses it
446       and writes any uncompressed data into $buffer. If the "Append"
447       parameter is set in the constructor, the uncompressed data will be
448       appended to the $buffer parameter. Otherwise $buffer will be
449       overwritten.
450
451       Returns the number of uncompressed bytes written to $buffer, zero if
452       eof or a negative number on error.
453
454   read
455       Usage is
456
457           $status = $z->read($buffer, $length)
458           $status = $z->read($buffer, $length, $offset)
459
460           $status = read($z, $buffer, $length)
461           $status = read($z, $buffer, $length, $offset)
462
463       Attempt to read $length bytes of uncompressed data into $buffer.
464
465       The main difference between this form of the "read" method and the
466       previous one, is that this one will attempt to return exactly $length
467       bytes. The only circumstances that this function will not is if end-of-
468       file or an IO error is encountered.
469
470       Returns the number of uncompressed bytes written to $buffer, zero if
471       eof or a negative number on error.
472
473   getline
474       Usage is
475
476           $line = $z->getline()
477           $line = <$z>
478
479       Reads a single line.
480
481       This method fully supports the use of the variable $/ (or
482       $INPUT_RECORD_SEPARATOR or $RS when "English" is in use) to determine
483       what constitutes an end of line. Paragraph mode, record mode and file
484       slurp mode are all supported.
485
486   getc
487       Usage is
488
489           $char = $z->getc()
490
491       Read a single character.
492
493   ungetc
494       Usage is
495
496           $char = $z->ungetc($string)
497
498   getHeaderInfo
499       Usage is
500
501           $hdr  = $z->getHeaderInfo();
502           @hdrs = $z->getHeaderInfo();
503
504       This method returns either a hash reference (in scalar context) or a
505       list or hash references (in array context) that contains information
506       about each of the header fields in the compressed data stream(s).
507
508   tell
509       Usage is
510
511           $z->tell()
512           tell $z
513
514       Returns the uncompressed file offset.
515
516   eof
517       Usage is
518
519           $z->eof();
520           eof($z);
521
522       Returns true if the end of the compressed input stream has been
523       reached.
524
525   seek
526           $z->seek($position, $whence);
527           seek($z, $position, $whence);
528
529       Provides a sub-set of the "seek" functionality, with the restriction
530       that it is only legal to seek forward in the input file/buffer.  It is
531       a fatal error to attempt to seek backward.
532
533       Note that the implementation of "seek" in this module does not provide
534       true random access to a compressed file/buffer. It  works by
535       uncompressing data from the current offset in the file/buffer until it
536       reaches the uncompressed offset specified in the parameters to "seek".
537       For very small files this may be acceptable behaviour. For large files
538       it may cause an unacceptable delay.
539
540       The $whence parameter takes one the usual values, namely SEEK_SET,
541       SEEK_CUR or SEEK_END.
542
543       Returns 1 on success, 0 on failure.
544
545   binmode
546       Usage is
547
548           $z->binmode
549           binmode $z ;
550
551       This is a noop provided for completeness.
552
553   opened
554           $z->opened()
555
556       Returns true if the object currently refers to a opened file/buffer.
557
558   autoflush
559           my $prev = $z->autoflush()
560           my $prev = $z->autoflush(EXPR)
561
562       If the $z object is associated with a file or a filehandle, this method
563       returns the current autoflush setting for the underlying filehandle. If
564       "EXPR" is present, and is non-zero, it will enable flushing after every
565       write/print operation.
566
567       If $z is associated with a buffer, this method has no effect and always
568       returns "undef".
569
570       Note that the special variable $| cannot be used to set or retrieve the
571       autoflush setting.
572
573   input_line_number
574           $z->input_line_number()
575           $z->input_line_number(EXPR)
576
577       Returns the current uncompressed line number. If "EXPR" is present it
578       has the effect of setting the line number. Note that setting the line
579       number does not change the current position within the file/buffer
580       being read.
581
582       The contents of $/ are used to determine what constitutes a line
583       terminator.
584
585   fileno
586           $z->fileno()
587           fileno($z)
588
589       If the $z object is associated with a file or a filehandle, "fileno"
590       will return the underlying file descriptor. Once the "close" method is
591       called "fileno" will return "undef".
592
593       If the $z object is associated with a buffer, this method will return
594       "undef".
595
596   close
597           $z->close() ;
598           close $z ;
599
600       Closes the output file/buffer.
601
602       For most versions of Perl this method will be automatically invoked if
603       the IO::Uncompress::UnXz object is destroyed (either explicitly or by
604       the variable with the reference to the object going out of scope). The
605       exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In these
606       cases, the "close" method will be called automatically, but not until
607       global destruction of all live objects when the program is terminating.
608
609       Therefore, if you want your scripts to be able to run on all versions
610       of Perl, you should call "close" explicitly and not rely on automatic
611       closing.
612
613       Returns true on success, otherwise 0.
614
615       If the "AutoClose" option has been enabled when the
616       IO::Uncompress::UnXz object was created, and the object is associated
617       with a file, the underlying file will also be closed.
618
619   nextStream
620       Usage is
621
622           my $status = $z->nextStream();
623
624       Skips to the next compressed data stream in the input file/buffer. If a
625       new compressed data stream is found, the eof marker will be cleared and
626       $.  will be reset to 0.
627
628       Returns 1 if a new stream was found, 0 if none was found, and -1 if an
629       error was encountered.
630
631   trailingData
632       Usage is
633
634           my $data = $z->trailingData();
635
636       Returns the data, if any, that is present immediately after the
637       compressed data stream once uncompression is complete. It only makes
638       sense to call this method once the end of the compressed data stream
639       has been encountered.
640
641       This option can be used when there is useful information immediately
642       following the compressed data stream, and you don't know the length of
643       the compressed data stream.
644
645       If the input is a buffer, "trailingData" will return everything from
646       the end of the compressed data stream to the end of the buffer.
647
648       If the input is a filehandle, "trailingData" will return the data that
649       is left in the filehandle input buffer once the end of the compressed
650       data stream has been reached. You can then use the filehandle to read
651       the rest of the input file.
652
653       Don't bother using "trailingData" if the input is a filename.
654
655       If you know the length of the compressed data stream before you start
656       uncompressing, you can avoid having to use "trailingData" by setting
657       the "InputLength" option in the constructor.
658

Importing

660       No symbolic constants are required by IO::Uncompress::UnXz at present.
661
662       :all Imports "unxz" and $UnXzError.  Same as doing this
663
664                use IO::Uncompress::UnXz qw(unxz $UnXzError) ;
665

EXAMPLES

SUPPORT

668       General feedback/questions/bug reports should be sent to
669       <https://github.com/pmqs/IO-Compress-Lzma/issues> (preferred) or
670       <https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress-Lzma>.
671

AUTHOR

688       This module was written by Paul Marquess, "pmqs@cpan.org".
689

MODIFICATION HISTORY

691       See the Changes file.
692

COPYRIGHT AND LICENSE

694       Copyright (c) 2005-2021 Paul Marquess. All rights reserved.
695
696       This program is free software; you can redistribute it and/or modify it
697       under the same terms as Perl itself.
698
699
700
701perl v5.34.0                      2021-07-22           IO::Uncompress::UnXz(3)