Question

I have a property that contains multiple values, and I want to execute a command with a separate “-j” argument for each value in the property.

E.g. <property name="arguments" value="foo bar hello world"/>

Should execute: mycommand -j foo -j bar -j hello -j world

I’m using Ant 1.7.1, so I can’t use the “prefix” attribute (Ant 1.8) on the <arg> element of an <exec> task.

One workaround is to insert the “-j” directly into the property by hand and then use the “line” attribute of <arg>:

<property name="args" value="-j foo -j bar -j hello -j world"/>
<exec executable="mycommand">
    <arg line="${args}"/>
</exec>

…But I prefer to have the property be a simple list without the embedded arguments.

Edit: Actually, my arguments are paths within an XML file, so a more accurate argument list would be:

<property name="arguments" value="/foo/bar /hello/world /a/very/long/path"/>

I would like the command to then execute with arguments: “-j /foo/bar -j /hello/world -j /a/very/long/path”. Note that the slashes remain forward slashes even under Windows (these are arguments to a command, not filenames).

Answer 1

You can use Ant resource tools for this.

<property name="arg_list" value="foo bar hello world"/>    
<resources id="arguments">
  <mappedresources>
    <string value="${arg_list}" />
    <filtermapper>
      <replacestring from=" " to=" -j "/>
    </filtermapper>
  </mappedresources>
</resources>
<property name="arguments" value="-j ${toString:arguments}" />

The above will result in property arguments having the value -j foo -j bar -j hello -j world, which can then be used in the exec arg line.

Alternatively a pathconvert task can help in this regard:

<property name="arg_list" value="foo bar hello world"/>    
<pathconvert property="arguments" pathsep=" ">
  <chainedmapper>
    <flattenmapper />
    <regexpmapper from="(.*)" to="-j \1" />
  </chainedmapper>
  <filelist files="${arg_list}" />
</pathconvert>

If you have absolute paths, rather than just strings in the list, then remove the flattenmapper.

If you have relative paths, replace the flattenmapper line with:

<globmapper from="${basedir}/*" to="*" />

to prevent the paths being converted to absolute.

In the event that you have UNIX-like paths in the arg_list on a Windows system the default settings for pathconvert won’t work – the paths get converted to Windows style. Instead, to process the list use:

<pathconvert property="arguments" pathsep=" " targetos="unix">
  <chainedmapper>
    <regexpmapper from="C:(.*)" to="-j \1" />
  </chainedmapper>
  <filelist files="${arg_list}" />
</pathconvert>

Note the targetos setting and the revised regexmapper from argument.