## Property

### Description

Sets a property (by name and value), or set of properties (from file or resource) in the project. Properties are case sensitive.

Properties are immutable: whoever sets a property first freezes it for the rest of the build; they are most definately not variable.

There are five ways to set properties:

- By supplying both the name and value attribute.
- By supplying both the name and refid attribute.
- By setting the file attribute with the filename of the property file to load. This property file has the format as defined by the file used in the class java.util.Properties.
- By setting the resource attribute with the resource name of the property file to load. This property file has the format as defined by the file used in the class java.util.Properties.
- By setting the environment attribute with a prefix to use. Properties will be defined for every environment variable by prefixing the supplied name and a period to the name of the variable.

Although combinations of these ways are possible, only one should be used at a time. Problems might occur with the order in which properties are set, for instance.

The value part of the properties being set, might contain references to other properties. These references are resolved at the time these properties are set. This also holds for properties loaded from a property file.

A list of predefined properties can be found here.

### Parameters

Attribute | Description | Required
name | the name of the property to set. | No
value | the value of the property. | One of these, when using the name attribute
location | Sets the property to the absolute filename of the given file. If the value of this attribute is an absolute path, it is left unchanged (with / and \ characters converted to the current platforms conventions). Otherwise it is taken as a path relative to the project's basedir and expanded.
refid | Reference to an object defined elsewhere. Only yields reasonable results for references to PATH like structures or properties.
resource | the resource name of the property file. | One of these, when not using the name attribute
file | the filename of the property file .
environment | the prefix to use when retrieving environment variables. Thus if you specify environment="myenv" you will be able to access OS-specific environment variables via property names "myenv.PATH" or "myenv.TERM". Note that if you supply a property name with a final "." it will not be doubled. ie environment="myenv." will still allow access of environment variables through "myenv.PATH" and "myenv.TERM". This functionality is currently only implemented on select platforms. Feel free to send patches to increase the number of platforms this functionality is supported on ;). Note also that properties are case sensitive, even if the environment variables on your operating system are not, e.g. it will be ${env.Path} not ${env.PATH} on Windows 2000.
classpath | the classpath to use when looking up a resource. | No
classpathref | the classpath to use when looking up a resource, given as reference to a <path> defined elsewhere.. | No
prefix | Prefix to apply to properties loaded using `file` or `resource`. A "." is appended to the prefix if not specified. | No

### Parameters specified as nested elements

#### classpath

`Property`'s classpath attribute is a PATH like structure and can also be set via a nested classpath element.

### Examples

      <property name="foo.dist" value="dist"/>

sets the property `foo.dist` to the value "dist".

      <property file="foo.properties"/>

reads a set of properties from a file called "foo.properties".

      <property resource="foo.properties"/>

reads a set of properties from a resource called "foo.properties".

Note that you can reference a global properties file for all of your Ant builds using the following:

      <property file="${user.home}/.ant-global.properties"/>

since the "user.home" property is defined by the Java virtual machine to be your home directory. This technique is more appropriate for Unix than Windows since the notion of a home directory doesn't exist on Windows. On the JVM that I tested, the home directory on Windows is "C:\". Different JVM implementations may use other values for the home directory on Windows.

      <property environment="env"/>
      <echo message="Number of Processors = ${env.NUMBER_OF_PROCESSORS}"/>
      <echo message="ANT_HOME is set to = ${env.ANT_HOME}"/>

reads the system environment variables and stores them in properties, prefixed with "env". Note that this only works on select operating systems. Two of the values are shown being echoed.

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