public Boolean call() throws Exception {
if (File.pathSeparatorChar==';') return false; // Windows
OutputStream o = Channel.current().getUnderlyingOutput();
if (o instanceof StandardOutputStream) {
StandardOutputStream stdout = (StandardOutputStream)o;
// duplicate the OS file descriptor and create FileOutputStream around it
int out = GNUCLibrary.LIBC.dup(1);
if (out<0) throw new IOException("Failed to dup(1)");
Constructor<FileDescriptor> c = FileDescriptor.class.getDeclaredConstructor(int.class);
c.setAccessible(true);
FileOutputStream fos = new FileOutputStream(c.newInstance(out));
// swap it into channel so that it'll use the new file descriptor
stdout.swap(fos);
// close fd=1 (stdout) and duplicate fd=2 (stderr) into fd=1 (stdout)
GNUCLibrary.LIBC.close(1);
GNUCLibrary.LIBC.dup2(2,1);
return true;