jar(1) | Basic Tools | jar(1) |
jar - Manipulates Java Archive (JAR) files.
Create JAR file
jar c[efmMnv0] [entrypoint] [jarfile] [manifest] [-C dir] file ... [-Joption ...] [@arg-file ...]
Update JAR file
jar u[efmMnv0] [entrypoint] [jarfile] [manifest] [-C dir] file ... [-Joption ...] [@arg-file ...]
Extract JAR file
jar x[vf] [jarfile] file ... [-Joption ...] [@arg-file ...]
List Contents of JAR file
jar t[vf] [jarfile] file ... [-Joption ...] [@arg-file ...]
Add Index to JAR file
jar i jarfile [-Joption ...] [@arg-file ...]
The jar command is a general-purpose archiving and compression tool, based on ZIP and the ZLIB compression format. However, the jar command was designed mainly to 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 (such as a browser) in a single HTTP transaction, rather than requiring a new connection for each piece. This dramatically improves download times. The jar command also compresses files, which further improves download time. The jar command also allows individual entries in a file to be signed by the applet author so that their origin can be authenticated. A JAR file can be used as a class path entry, whether or not it is compressed.
The syntax for the jar command resembles the syntax for the tar command. It has several operation modes, defined by one of the mandatory operation arguments. Other arguments are either options that modify the behavior of the operation, or operands required to perform the operation.
When using the jar command, you have to select an operation to be performed by specifying one of the following operation arguments. You can mix them up with other one-letter options on the command line, but usually the operation argument is the first argument specified.
Use the following options to customize how the JAR file is created, updated, extracted, or viewed:
For example, the following command creates the Main.jar archive with the Main.class file where the Main-Class attribute value in the manifest is set to Main:
jar cfe Main.jar Main Main.class
The Java Runtime Environment (JRE) can directly call this application by running the following command:
java -jar Main.jar
If the entry point class name is in a package, then it could use either the dot (.) or slash (/) as the delimiter. For example, if Main.class is in a package called mydir, then the entry point can be specified in one of the following ways:
jar -cfe Main.jar mydir/Main mydir/Main.class
jar -cfe Main.jar mydir.Main mydir/Main.class
Note
Specifying both m and e options together when a particular manifest also contains the Main-Class attribute results in an ambiguous Main-Class specification. The ambiguity leads to an error and the jar command creation or update operation is terminated.
You can add special-purpose name-value attribute pairs to the manifest that are not contained in the default manifest file. For example, you can add attributes that specify vendor information, release information, package sealing, or to make JAR-bundled applications executable. For examples of using the m option, see Packaging Programs at http://docs.oracle.com/javase/tutorial/deployment/jar/index.html
jar uf my.jar -C classes Bar.class
The following command changes to the classes directory and adds to my.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 my.jar.
jar uf my.jar -C classes . -C bin Xyz.class
If classes contained files bar1 and bar2, then the JAR file will contain the following after running the previous command:
% jar tf my.jar
META-INF/
META-INF/MANIFEST.MF
bar1
bar2
Xyz.class
The following operands are recognized by the jar command.
When indexing (i) a JAR file, specify the jarfile operand without the f option.
An argument file can include options and arguments of the jar command (except the -J options, because they are passed to the launcher, which does not support argument files). The arguments within a file can be separated by spaces or newline characters. File names within an argument file are relative to the current directory from which you run the jar command, not relative to the location of the argument file. Wild cards, such as the asterisk (*), that might otherwise be expanded by the operating system shell, are not expanded.
The following example, shows how to create a classes.list file with names of files from the current directory output by the find command:
find . -name '*.class' -print > classes.list
You can then execute the jar command and pass the classes.list file to it using the @arg-file syntax:
jar cf my.jar @classes.list
An argument file can be specified with a path, but any file names inside the argument file that have relative paths are relative to the current working directory of the jar command, not to the path passed in, for example:
jar @dir/classes.list
The e, f, and m options must appear in the same order on the command line as the entrypoint, jarfile, and manifest operands, for example:
jar cmef myManifestFile MyMainClass myFile.jar *.class
Example 1 Adding All Files From the Current Directory With Verbose Output
% 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%)
Example 2 Adding Files From Subdirectories
% 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/
Example 3 Listing the Contents of JAR
% 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
Example 4 Adding an Index
Use the i option when you split the interdependent 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, then you can use the i option to speed up the class loading time for your application:
Class-Path: buy.jar sell.jar
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 application class loader uses the information stored in this file for efficient class loading. To copy directories, first compress files in dir1 to stdout, then pipeline and extract from stdin to dir2 (omitting the -f option from both jar commands):
(cd dir1; jar c .) | (cd dir2; jar x)
21 November 2013 | JDK 8 |