[Discuss-gnuradio] control of message_source flowgraph

[Ben Hiett]

I have a top block with two flow graphs in it


both of which are defined as hier blocks

one flowgraph consists of a message source that writes to a file sink

the other flowgraph detects an incoming signal (from a usrp2 source) and writes 
n samples of it to the message source

each time the file sink is written to I would like to copy and rename that file 
and delete the original 

therefore I can obtain multiple files of signals I've detected and not just 
append to the same file each time a subsequent signal is detected

what I can't quite figure out is how to trigger the copy/rename/delete of the 
file sink file

e.g. is there an event of some sort I can use when the message source flowgraph 
completes?

I have looked at some of the relevant files e.g. rx_voice.py and I have a 
suspicion i could do it with a callback function but I can't quite see how it 
works

any pointers gratefully received

PS is it still the case you cannot have multiple instances of top_block (i seem 
to have managed it without any error messages)