I already referred the above link. using that i am able to get attachments in source list. But not from task attachments.
In below image as you can see we have to enter the listName. There i am not getting option to enter the task list name. If i hard code the name of workflow task list web service is failing.
Have you tried adding the name of the list in the variable and then referencing that variable in the listName parameter? The Web service should work as explained by Vadin here.
I dint try by saving the name into a variable, instead I directly wrote in list name section. I will try your suggestion.
I have one more doubt in vadim’s link, do I need to install the file .uda?
what error do you get for task list?
web service call configuration is quite straightforward
note this webservice method returns just attachment links. to get attachment's content itself you'll have to use following Vadim's UDA - Nintex Workflow - Get List Item Attachment in Base64 Custom Action (Happy Thanksgiving) - Vadim Taba...
so that's about how to get either task's attachments links or content into workflow.
to be able to access task's attachments from source list item, you can either populate (all the) links into a field (typically rich enabled multiline text field), or you can copy over whole attachments (content). for details see the link Kapil Joshi posted above