pack200 Man page

Resume Wikipedia de Nombre magique (programmation)

En programmation informatique, le terme magic number (en français « nombre magique ») peut désigner :
une constante numérique ou un ensemble de caractères utilisé pour désigner un format de fichier ou un protocole ;
une constante numérique non nommée ou mal documentée ;
un ensemble de valeurs ayant un sens particulier (par exemple, les GUID).

(en) The Linux Information Project, « Magic Number Definition »,‎ 21 août 2006 (consulté le 19 novembre 2009)

pack200 Java Deployment Tools pack200


pack200 – Packages a JAR file into a compressed pack200 file for web


pack200 [options] output-file JAR-file

Options can be in any order. The last option on the command line or in
a properties file supersedes all previously specified options.

The command-line options. See Options.

Name of the output file.

Name of the input file.


The pack200 command is a Java application that transforms a JAR file
into a compressed pack200 file with the Java gzip compressor. The
pack200 files are highly compressed files that can be directly deployed
to save bandwidth and reduce download time.

The pack200 command has several options to fine-tune and set the
compression engine. The typical usage is shown in the following
example, where myarchive.pack.gz is produced with the default pack200
command settings:

pack200 myarchive.pack.gz myarchive.jar


-r, –repack
Produces a JAR file by packing and unpacking a JAR file. The
resulting file can be used as an input to the jarsigner tool.
The following example packs and unpacks the myarchive.jar file:

pack200 –repack myarchive-packer.jar myarchive.jar
pack200 –repack myarchive.jar

The following example preserves the order of files in the input

-g, –no-gzip
Produces a pack200 file. With this option, a suitable compressor
must be used, and the target system must use a corresponding

pack200 –no-gzip myarchive.pack myarchive.jar

-G, –strip-debug
Strips debugging attributes from the output. These include
SourceFile, LineNumberTable, LocalVariableTable and
LocalVariableTypeTable. Removing these attributes reduces the
size of both downloads and installations, but reduces the
usefulness of debuggers.

Preserve the order of files in the input file. This is the
default behavior.

-O, –no-keep-file-order
The packer reorders and transmits all elements. The packer can
also remove JAR directory names to reduce the download size.
However, certain JAR file optimizations, such as indexing, might
not work correctly.

-Svalue , –segment-limit=value
The value is the estimated target size N (in bytes) of each
archive segment. If a single input file requires more than N
bytes, then its own archive segment is provided. As a special
case, a value of -1 produces a single large segment with all
input files, while a value of 0 produces one segment for each
class. Larger archive segments result in less fragmentation and
better compression, but processing them requires more memory.

The size of each segment is estimated by counting the size of
each input file to be transmitted in the segment with the size
of its name and other transmitted properties.

The default is -1, which means that the packer creates a single
segment output file. In cases where extremely large output files
are generated, users are strongly encouraged to use segmenting
or break up the input file into smaller JARs.

A 10 MB JAR packed without this limit typically packs about 10
percent smaller, but the packer might require a larger Java heap
(about 10 times the segment limit).

-Evalue , –effort=value
If the value is set to a single decimal digit, then the packer
uses the indicated amount of effort in compressing the archive.
Level 1 might produce somewhat larger size and faster
compression speed, while level 9 takes much longer, but can
produce better compression. The special value 0 instructs the
pack200 command to copy through the original JAR file directly
with no compression. The JSR 200 standard requires any unpacker
to understand this special case as a pass-through of the entire

The default is 5, to invest a modest amount of time to produce
reasonable compression.

-Hvalue , –deflate-hint=value
Overrides the default, which preserves the input information,
but can cause the transmitted archive to be larger. The possible
values are: true, false, or keep.

If the value is true or false, then the packer200 command sets
the deflation hint accordingly in the output archive and does
not transmit the individual deflation hints of archive elements.

The keep value preserves deflation hints observed in the input
JAR. This is the default.

-mvalue , –modification-time=value
The possible values are latest and keep.

If the value is latest, then the packer attempts to determine
the latest modification time, among all the available entries in
the original archive, or the latest modification time of all the
available entries in that segment. This single value is
transmitted as part of the segment and applied to all the
entries in each segment. This can marginally decrease the
transmitted size of the archive at the expense of setting all
installed files to a single date.

If the value is keep, then modification times observed in the
input JAR are preserved. This is the default.

-Pfile , –pass-file=file
Indicates that a file should be passed through bytewise with no
compression. By repeating the option, multiple files can be
specified. There is no pathname transformation, except that the
system file separator is replaced by the JAR file separator
forward slash (/). The resulting file names must match exactly
as strings with their occurrences in the JAR file. If file is a
directory name, then all files under that directory are passed.

-Uaction , –unknown-attribute=action
Overrides the default behavior, which means that the class file
that contains the unknown attribute is passed through with the
specified action. The possible values for actions are error,
strip, or pass.

If the value is error, then the entire pack200 command operation
fails with a suitable explanation.

If the value is strip, then the attribute is dropped. Removing
the required Java Virtual Machine (JVM) attributes can cause
class loader failures.

If the value is pass, then the entire class is transmitted as
though it is a resource.

-Cattribute-name=layout , –class-attribute=attribute-name=action
See next option.

-Fattribute-name=layout , –field-attribute=attribute-name=action
See next option.

-Mattribute-name=layout , –method-attribute=attribute-name=action
See next option.

-Dattribute-name=layout , –code-attribute=attribute-name=action
With the previous four options, the attribute layout can be
specified for a class entity, such as class-attribute, field-
attribute, method-attribute, and code-attribute. The attribute-
name is the name of the attribute for which the layout or action
is being defined. The possible values for action are some-
layout-string, error, strip, pass.

some-layout-string: The layout language is defined in the JSR
200 specification, for example: –class-

If the value is error, then the pack200 operation fails with an

If the value is strip, then the attribute is removed from the
output. Removing JVM-required attributes can cause class loader
failures. For example, –class-attribute=CompilationID=pass
causes the class file that contains this attribute to be passed
through without further action by the packer.

If the value is pass, then the entire class is transmitted as
though it is a resource.

-f , –
A configuration file, containing Java properties to initialize
the packer, can be specified on the command line.

pack200 -f myarchive.pack.gz myarchive.jar
# Generic properties for the packer.
# This option will cause the files bearing new attributes to
# be reported as an error rather than passed uncompressed.
# Change the segment limit to be unlimited.

-v, –verbose
Outputs minimal messages. Multiple specification of this option
will create more verbose messages.

-q, –quiet
Specifies quiet operation with no messages.

-lfilename , –log-file=filename
Specifies a log file to output messages.

-?, -h, –help
Prints help information about this command.

-V, –version
Prints version information about this command.

Passes the specified option to the Java Virtual Machine. For
more information, see the reference page for the java
command. For example, -J-Xms48m sets the startup memory to 48

The following exit values are returned: 0 for successful completion and
a number greater than 0 when an error occurs.

This command should not be confused with pack(1). The pack and pack200
commands are separate products.

The Java SE API Specification provided with the JDK is the superseding
authority, when there are discrepancies.


· unpack200

· jar

· jarsigner

JDK 8 21 November 2013 pack200

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