Ant task to determine if a file is readonly - ant

Question

I need to write an ant task to determine if a certain file is readonly, and if it is, fail. I would like to avoid using a custom selector to do this do to the nature of our build system. Anyone have any ideas how to go about doing this? I'm using ant 1.8 + ant-contrib.
Thanks!

Answer 1

Will something like this do the trick?
<condition property="file.is.readonly">
<not>
<isfileselected file="${the.file.in.question}">
<writable />
</isfileselected>
</not>
</condition>
<fail if="file.is.readonly" message="${the.file.in.question} is not writeable" />
This uses the condition task and the isfileselected condition (not a direct link - you'll have to search down the page) combined with the writable selector (and reversed with a not condition).
Update:
An possibly better alternative would be:
<fail message="${the.file.in.question} is not writeable">
<condition>
<not>
<isfileselected file="${the.file.in.question}">
<writable />
</isfileselected>
</not>
</condition>
</fail>
This has the check and the fail as one distinct action rather than two, so you may find it clearer, and it doesn't require using a property name, so your namespace is cleaner.

Answer 2

I'm sure there are better ways but I'll throw a few possible methods out there.
Use the copy task to create a temp duplicate then attempt to copy this file to overwrite the original. The failonerror attribute will come in handy
Use the java task to execute a task which executes some simple code such as:
File f = new File( path );
f.canWrite()......

Answer 3

What about writing a custom condition to be used by the condition task? It is more flexible.
public class IsReadOnly extends ProjectComponent implements Condition
{
private Resource resource;
/**
* The resource to test.
*/
public void add(Resource r) {
if (resource != null) {
throw new BuildException("only one resource can be tested");
}
resource = r;
}
/**
* Argument validation.
*/
protected void validate() throws BuildException {
if (resource == null) {
throw new BuildException("resource is required");
}
}
public boolean eval() {
validate();
if (resource instanceof FileProvider) {
return !((FileProvider)resource).getFile().canWrite();
}
try {
resource.getOutputStream();
return false;
} catch (FileNotFoundException no) {
return false;
} catch (IOException no) {
return true;
}
}
}
Integrate with
<typedef
name="isreadonly"
classname="IsReadOnly"
classpath="${myclasses}"/>
and use it like
<condition property="readonly">
<isreadonly>
<file file="${file}"/>
</isreadonly>
</condition>