How to find out if a specific file has been checked out to specific task?

Here is the command for you:

ccm query -name <file name>"status='working' and is_associated_object_of('task<task number>#1:task:probtrac')" -u -f TRUE

for example:

$> ccm query -name strings.xml "status='working' and is_associated_object_of('task202873#1:task:probtrac')" -u -TRUE

If the file IS associated with THE task, you will get a line of the output with a single word "TRUE", if not - you will get a "new line" only:

$> TRUE

Enjoy :)