execute shell script

hi

i am trying to execute a shell script within my xpi installation. i 
wrote a very simple test.sh:

-------------test.sh-------------
#!/bin/sh

mkdir /tmp/t
---------------------------------

-------------install.js----------
...
var r = execute("test.sh");
logComment("execute test.sh returned " + r);
...
---------------------------------

-------------install.log---------
** initInstall: 0
** execute test.sh returned 0
** plugins folder: /popeye/usr/lib/mozilla-1.2.1/plugins/
[1/2]	Executing: /tmp/xpinstall.sh
[2/2]	Replacing: 	/popeye/usr/lib/mozilla-1.2.1/plugins/libspcweb.so
** performInstall() returned: 0

Install completed successfully  --  01/05/2004 15:05:08
---------------------------------

as you can see everthing is fine in the install.log,
but there is no directory /tmp/t.

any ideas?

thanks
chris