jar-The Java Archive Tool


Documentation Contents


p, li {font-size: medium;
font-family: serif}

code, tt, pre {font-size: 125%;
font-family: monospace;
font-weight;
color: black;
}

.red {color: red }



jar-The Java Archive Tool

jar combines multiple files into a single JAR archive file.


Synopsis
Description
Options
Command Line Argument Files
Examples
See Also




SYNOPSIS





Create jar file
jar c[v0Mmfe] [manifest] [jarfile] [entrypoint] [-C dir] inputfiles [-Joption]


Update jar file
jar u[v0Mmfe] [manifest] [jarfile] [entrypoint] [-C dir] inputfiles [-Joption]


Extract jar file
jar x[vf] [jarfile] [inputfiles] [-Joption]


List table of contents of jar file
jar t[vf] [jarfile] [inputfiles] [-Joption]


Add index to jar file
jar i jarfile [-Joption]




where:



cuxtiv0Mmfe
Options that control the jar command.



jarfile
Jar file to be created (c),
updated (u), extracted (x),
or have its table of contents viewed (t).
The -f option and filename jarfile
are a pair -- if either is present, they must both appear.
Note that omitting f and jarfile
accepts a "jar file" from standard input (for x and t)
or sends the "jar file" to standard output (for c and u).



inputfiles
Files or directories, separated by spaces, to be combined
into jarfile (for c and u), or to be extracted
(for x) or listed (for t) from jarfile.
All directories are processed recursively. The files
are compressed unless option 0 (zero) is used.



manifest
Pre-existing manifest file whose
name: value
pairs are to be included in MANIFEST.MF in the jar file.
The -m option and filename manifest
are a pair -- if either is present, they must both appear.
The letters m, f and e must appear in
the same order that manifest, jarfile,
entrypoint appear.



entrypoint
The name of the class that set as the application entry
point for stand-alone applications bundled into
executable jar file. The -e option and entrypoint
are a pair -- if either is present, they must both appear.
The letters m, f and e must appear in
the same order that manifest, jarfile,
entrypoint appear.


-C dir
Temporarily changes directories to dir while
processing the following inputfiles argument.
Multiple -C dir inputfiles
sets are allowed.


-Joption
Option to be passed into the Java runtime environment.
(There must be no space between -J and
option).








DESCRIPTION

The jar tool combines multiple
files into a single JAR archive file. jar is a general-purpose archiving
and compression tool, based on ZIP and the ZLIB
compression format. However, jar was designed mainly package java applets or applications into a single archive. When
the components of an applet or application (files, images and sounds)
are combined into a single archive, they can be downloaded by a java agent
(like a browser) in a single HTTP transaction, rather than requiring a
new connection for each piece. This dramatically improves download times.
jar also compresses files and so further improves download time.
In addition, it allows individual entries in a file to be signed by the
applet author so that their origin can be authenticated. The syntax for
the jar tool is almost identical to the syntax for the tar command.
A jar archive can be used as a class path
entry, whether or not it is compressed.


Typical usage to combine files into a jar file is:

% jar cf myFile.jar *.class


In this example, all the class files in the current directory are placed
into the file named myFile.jar. The jar tool automatically generates a manifest file entry named
META-INF/MANIFEST.MF. It is always the first entry in the jar file. The manifest file declares meta-information about the archive, and stores that data as
name : value pairs.
Refer to the JAR file
specification for details explaining how the jar tool stores meta-information in the manifest file.

If a jar file should include name : value pairs contained in an existing manifest file, specify that file using the -m option:


% jar cmf myManifestFile myFile.jar *.class


An existing manifest file must end with a
new line character.  jar does not parse the last line of a manifest file if it does not end with a new line character.

Note:  A jar command that specifies cfm on the command line instead of cmf (the
order of the m and -f options are reversed), the jar command line must specify the name of the
jar archive first, followed by the name of the manifest file:

% jar cfm myFile.jar myManifestFile *.class


The manifest is in a text format inspired by RFC822 ASCII format,
so it is easy to view and process manifest-file contents.

To extract the files from a jar file, use x:

% jar xf myFile.jar


To extract individual files from a jar file, supply their filenames:

% jar xf myFile.jar foo bar


Beginning with version 1.3 of the Java 2 SDK, the jar utility
supports JarIndex,
which allows application class loaders to load classes more efficiently from
jar files. If an application or applet is bundled into multiple jar
files, 
only the necessary jar files will be downloaded and opened to load classes.
This performance optimization is enabled by running jar with the
-ioption. It will generate package location information for
the specified main jar file and all the jar files it depends on, which
need to be specified in the Class-Path attribute of the main jar
file's manifest.
% jar i main.jar


In this example, an INDEX.LIST file is inserted into the META-INF directory
of main.jar.
The application class loader uses the information stored in this
file for efficient class loading. 
For details about how location information is stored in the index file, refer to the JarIndex specification.


To copy directories, first compress files in dir1
to stdout, then extract from stdin to dir2 (omitting the
-f option from both jar commands):

% (cd dir1; jar c .) | (cd dir2; jar x)


To review command samples which use jar to opeate on jar files and jar file manifests, see Examples, below. Also refer to the jar trail
of the Java Tutorial.





OPTIONS






c


Creates a new archive file named jarfile
(if f is specified) or to standard output
(if f and jarfile are omitted).
Add to it the files and directories specified by
inputfiles.




u


Updates an existing file jarfile (when
f is specified) by adding to it files
and directories specified by
inputfiles.

For example:


jar uf foo.jar foo.class


would add the file foo.class to the existing jar file foo.jar.
The -u option can also update the manifest
entry, as given by this example:


jar umf manifest foo.jar


updates the foo.jar manifest with the
name : value pairs in
manifest.





x


Extracts files and directories from
jarfile (if f
is specified) or standard input (if f and
jarfile are omitted). If
inputfiles
is specified, only those specified files and directories
are extracted. Otherwise, all files and directories are
extracted. The time and date of the extracted files are
those given in the archive.




t


Lists the table of contents from
jarfile (if f
is specified) or standard input (if f and
jarfile are omitted). If
inputfiles
is specified, only those specified files and directories
are listed. Otherwise, all files and directories are
listed.




i
Generate index information for the specified
jarfile and its
dependent jar files. For example:

jar i foo.jar

would generate an INDEX.LIST file in foo.jar which
contains location information for each package in foo.jar and
all the jar files specified in the Class-Path attribute
of foo.jar.

See the index example.




f


Specifies the file jarfile
to be created (c),
updated (u), extracted (x),
indexed (i), or viewed (t).
The -f option and filename jarfile
are a pair -- if present, they must both appear.
Omitting f and jarfile accepts a jar file name
from stdin(for x and t) or sends jar file to
stdout (for c and u).




v


Generates verbose output to standard output.
Examples shown below.




0


(zero) Store without using ZIP compression.




M


Do not create a manifest file entry (for c and u),
or delete a manifest file entry if one exists (for u).




m


Includes name : value attribute pairs from the
specified manifest file manifest in the file at
META-INF/MANIFEST.MF. jar adds a name : value
pair unless an entry already exists with the same
name, in which case jar updates its value.


On the command line, the letters m and f must appear in
the same order that manifest and jarfile appear.
Example use:


jar cmf myManifestFile myFile.jar *.class


You can add special-purpose name : value
attribute pairs to the manifest that aren't contained in the default manifest. For example, you can add attributes specifying vendor
information, version information,
package sealing, or to make JAR-bundled applications executable.
See the JAR
Files trail in the Java Tutorial for examples of using the -m
option.





e


Sets entrypoint as the application entry
point for stand-alone applications bundled into executable jar file.
The use of this option creates or overrides the Main-Class attribute
value in the manifest file.

This option can be used during creation of jar
file or while updating the jar file.


This option specifies the application entry point without editing or
creating the manifest file.


For example, this command creates Main.jar where the Main-Class attribute value in the manifest is set to Main:


jar cfe Main.jar Main Main.class



The java runtime can directly invoke this application by running the following command:



java -jar Main.jar


If the entrypoint class name is in a package it may use either a dot (".")
or slash ("/") character as the delimiter.
For example, if Main.class is in a package called
foo the entry point can be specified in the following ways:

jar -cfe Main.jar foo/Main foo/Main.class

or

jar -cfe Main.jar foo.Main foo/Main.class


Note:  specifying both -m and -e options together when the given
manifest also contains the Main-Class attribute results in an ambigous
Main.class specification, leading to an error and the jar creation or
update operation is aborted.




-C  dir


Temporarily changes directories (cd dir)
during execution of the jar command
while processing the following inputfiles argument. Its
operation is intended to be similar to the -C option of
the UNIX tar utility.

For example, this command changes to the classes directory and adds the bar.class
from that directory to foo.jar:


jar uf foo.jar -C classes bar.class


This command changes to the classes directory and adds to foo.jar
all files within the classes directory (without creating
a classes directory in the jar file), then changes back to the
original directory before changing to the bin directory
to add xyz.class to foo.jar.


jar uf foo.jar -C classes . -C bin xyz.class


If classes
holds files bar1 and bar2, then here's
what the jar file will contain using jar tf foo.jar:


META-INF/
META-INF/MANIFEST.MF
bar1
bar2
xyz.class







-Joption
Pass option to the Java runtime environment, where
option is one of the options described on the
reference page for the java application
launcher. For example, -J-Xmx48M sets the
maximum memory to 48 megabytes. It is a common convention for -J
to pass options to the underlying runtime environment.







COMMAND LINE ARGUMENT FILES


To shorten or simplify the jar command line, you can
specify one or more files that themselves contain
arguments to the jar command (except
-J options). This enables you to create
jar commands of any length, overcoming command line limits
imposed by the operating system.


An argument file can include options and filenames.
The arguments within a file can be space–separated or newline-separated.
Filenames within an argument file are relative to the current
directory, not relative to the location of the argument file. Wildcards (*)
that might otherwise be expanded by the operating system shell
are not expanded. Use of the @ character to recursively
interpret files is not supported. The -J options are
not supported because they are passed to the launcher, which
does not support argument files.


When executing jar, pass in the path and name of each argument
file with the @ leading character.
When jar encounters an argument beginning with
the character @, it expands the contents of
that file into the argument list.

The example below, classes.list holds the names of files output by a find command:



% find . -name '*.class' -print > classes.list


You can then execute the jar command on Classes.list by passing it to jar using argfile syntax:
% jar cf my.jar @classes.list


An argument file can specify a path, but any
filenames inside the argument file that have relative paths
are relative to the current working directory, not to the
path passed in. Here is an example:
% jar @path1/classes.list






EXAMPLES


To add all the files in a particular directory to an archive
(overwriting contents if the archive already exists). Enumerating
verbosely (with the -v option) will tell you more information about
the files in the archive, such as their size and last modified date.

% ls
1.au Animator.class monkey.jpg
2.au Wave.class spacemusic.au
3.au at_work.gif

% jar cvf bundle.jar *
added manifest
adding: 1.au(in = 2324) (out= 67)(deflated 97%)
adding: 2.au(in = 6970) (out= 90)(deflated 98%)
adding: 3.au(in = 11616) (out= 108)(deflated 99%)
adding: Animator.class(in = 2266) (out= 66)(deflated 97%)
adding: Wave.class(in = 3778) (out= 81)(deflated 97%)
adding: at_work.gif(in = 6621) (out= 89)(deflated 98%)
adding: monkey.jpg(in = 7667) (out= 91)(deflated 98%)
adding: spacemusic.au(in = 3079) (out= 73)(deflated 97%)




If you already have separate subdirectories for images, audio files
and classes, you can combine them into a single jar file:



% ls -F
audio/ classes/ images/

% jar cvf bundle.jar audio classes images
added manifest
adding: audio/(in = 0) (out= 0)(stored 0%)
adding: audio/1.au(in = 2324) (out= 67)(deflated 97%)
adding: audio/2.au(in = 6970) (out= 90)(deflated 98%)
adding: audio/3.au(in = 11616) (out= 108)(deflated 99%)
adding: audio/spacemusic.au(in = 3079) (out= 73)(deflated 97%)
adding: classes/(in = 0) (out= 0)(stored 0%)
adding: classes/Animator.class(in = 2266) (out= 66)(deflated 97%)
adding: classes/Wave.class(in = 3778) (out= 81)(deflated 97%)
adding: images/(in = 0) (out= 0)(stored 0%)
adding: images/monkey.jpg(in = 7667) (out= 91)(deflated 98%)
adding: images/at_work.gif(in = 6621) (out= 89)(deflated 98%)

% ls -F
audio/ bundle.jar classes/ images/




To see the entry names in the jarfile, use the t option:



% jar tf bundle.jar
META-INF/
META-INF/MANIFEST.MF
audio/1.au
audio/2.au
audio/3.au
audio/spacemusic.au
classes/Animator.class
classes/Wave.class
images/monkey.jpg
images/at_work.gif







To add an index file to the jar file for speeding up class loading,
use the i option. Example:




If you split the inter-dependent classes for a stock trade application
into three jar files: main.jar, buy.jar,
and sell.jar. If you specify the Class-path attribute
in the main.jar manifest as:

Class-Path: buy.jar sell.jar

then you can use the -i option to speed up the class loading time for your application:

% jar i main.jar

An INDEX.LIST file is inserted to the META-INF directory. This enables the application class loader to download the specified jar files when it is
searching for classes or resources.








SEE ALSO

The Jar Overview

The Jar File Specification

The JarIndex Spec

Jar Tutorial
on the Java Software web site.
pack200 Reference Page









Copyright © 1995-2010 Sun Microsystems, Inc. All Rights Reserved. Please send comments using this Feedback page.

Java Technology