jar-The Java Archive Tool
jar combines multiple files into a single JAR archive file.
Create jar file
jar c[v0Mmfe] [manifest] [jarfile] [entrypoint] [-C dir] inputfiles
Update jar file
jar u[v0Mmfe] [manifest] [jarfile] [entrypoint] [-C dir] inputfiles
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]
Options that control the jar command.
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).
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.
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.
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.
Temporarily changes directories to dir while processing the
following inputfiles argument. Multiple -C dir inputfiles sets
Option to be passed into the Java runtime environment. (There
must be no space between -J and option).
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 @
http://www.gzip.org/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 @
http://ccc.sfbay/4291383/attachment/classpath.html 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 @
http://ccc.sfbay/guide/jar/jar.html#JAR%20Manifest for details
explaining how the jar tool stores meta-information in the manifest
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
http://ccc.sfbay/guide/jar/jar.html#JAR%20Index, 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
% 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
To copy directories, first compress files in dir1 to stdout, then
extract from stdin to dir2 (omitting the -f option from both jar
% (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 @
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 @
http://java.sun.com/docs/books/tutorial/jar/ 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
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
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
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.
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
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:
Pass option to the Java runtime environment, where option is one of
the options described on the reference page for the java application
http://ccc.sfbay/4291383/attachment/java.html#options. 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
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
The example below, classes.list holds the names of files output by a
% 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
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.
1.au Animator.class monkey.jpg
2.au Wave.class spacemusic.au
% jar cvf bundle.jar *
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
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
To add an index file to the jar file for speeding up class loading, use
the i option.
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.
The Jar Overview @
The Jar File Specification @
The JarIndex Spec @
Jar Tutorial @
http://java.sun.com/docs/books/tutorial/jar on the Java Software web
pack200 Reference Page @
05 Aug 2006 jar(1)