Synopsis

jar c|t|u|x[f][m][M][0][v] [jar-file] [manifest] [-C directory] [input-files]
jar i [jar-file]

Description

jar is a tool that can create and manipulate Java Archive ( JAR) files. A JAR file is a ZIP file that contains Java class files, auxiliary resource files required by those classes, and optional meta-information. This meta-information includes a manifest file that lists the contents of the JAR archive and provides auxiliary information about each file.

The jar command can create JAR files, list the contents of JAR files, and extract files from a JAR archive. In Java 1.2 and later, it can also add files to an existing archive or update the manifest file of an archive. In Java 1.3 and later, jar can also add an index entry to a JAR file.

The syntax of the jar command is reminiscent of the Unix tar (tape archive) command. Most options to jar are specified as a block of concatenated letters passed as a single argument rather than as individual command-line arguments. The first letter of the first argument specifies what action jar is to perform; it is required. Other letters are optional. The various file arguments depend on which letters are specified.

As in javac, any command-line argument that begins with @ is taken to be the name of a file that contains options or filenames.

Command options

The first letter of the first option to jar specifies the basic operation jar is to perform. The available options are:

c

Creates a new JAR archive. A list of input files and/or directories must be specified as the final arguments to jar. The newly created JAR file has a META-INF/MANIFEST.MF file as its first entry. This automatically created manifest lists the contents of the JAR file and contains a message digest for each file.

i

Indexes the contents of this JAR file as well as the contents of all JAR files it refers to in the Class-Path manifest attribute. The resulting index is stored in the JAR file as META-INF/INDEX.LIST and can be used by a Java interpreter or applet viewer to optimize its class and resource lookup algorithm and avoid downloading unnecessary JAR files. This i option must be followed by the name of the JAR file to be indexed. No other options are allowed. Java 1.3 and later.

t

Lists the contents of a JAR archive.

u

Updates the contents of a JAR archive. Any files listed on the command line are added to the archive. When used with the m option, this adds the specified manifest information to the JAR file. Java 1.2 and later.

x

Extracts the contents of a JAR archive. The files and directories specified on the command line are extracted and created in the current working directory. If no file or directory names are specified, all the files and directories in the JAR file are extracted.

Modifier options

Each of the four command specifier letters can be followed by additional letters that provide further detail about the operation to be performed:

f

Indicates that jar is to operate on a JAR file whose name is specified on the command line. If this option is not present, jar reads a JAR file from standard input and/or writes a JAR file to standard output. If the f option is present, the command line must contain the name of the JAR file to operate on.

m

When jar creates or updates a JAR file, it automatically creates (or updates) a manifest file named META-INF/MANIFEST.MF in the JAR archive. This default manifest simply lists the contents of the JAR file. Many JAR files require additional information to be specified in the manifest; the m option tells the jar command that a manifest template is specified on the command line. jar reads this manifest file and stores all the information it contains into the META-INF/MANIFEST.MF file it creates. This m option should be used only with the c or u commands, not with the t or x commands.

M

Used with the c and u commands to tell jar not to create a default manifest file.

v

Tells jar to produce verbose output.

0

Used with the c and u commands to tell jar to store files in the JAR archive without compressing them. Note that this option is the digit zero, not the letter O.

Files

The first option to jar consists of an initial command letter and various option letters. This first option is followed by a list of files:

jar-file

If the first option contains the letter f, that option must be followed by the name of the JAR file to create or manipulate.

manifest-file

If the first option contains the letter m, that option must be followed by the name of the file that contains manifest information. If the first option contains both the letters f and m, the JAR and manifest files should be listed in the same order the f and m options appear. jar automatically creates a manifest for the JAR file it creates unless the M option is specified. The manifest-file specified with the m option should contain additional manifest entries to be placed in the manifest in addition to the automatically generated entries.

files

The list of one or more files and/or directories to be inserted into or extracted from the JAR archive.

Additional options

In addition to all the options listed previously, jar also supports the following:

-C dir

Used within the list of files to process; it tells jar to change to the specified dir while processing the subsequent files and directories. The subsequent file and directory names are interpreted relative to dir and are inserted into the JAR archive without dir as a prefix. Any number of -C options can be used; each remains in effect until the next is encountered. The directory specified by a -C option is interpreted relative to the current working directory, not the directory specified by the previous -C option. Java 1.2 and later.

-J javaopt

Passes the option javaopt to the Java interpreter.

Examples

The jar command has a confusing array of options, but, in most cases, its use is quite simple. To create a simple JAR file that contains all the class files in the current directory and all files in a subdirectory called images, you can type:

% jar cf my.jar *.class images

To verbosely list the contents of a JAR archive:

% jar tvf your.jar

To extract the manifest file from a JAR file for examination or editing:

% jar xf the.jar META-INF/MANIFEST.MF

To update the manifest of a JAR file:

% jar ufm my.jar manifest.template

See also

jarsigner