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 JDK, 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 Packaging Programs in JAR Files lesson 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

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