Thanks Thomas for your post, it helped me too, but there is one more thing i still would like to understand, in the question rascal asked for running a rostopic echo from a launch, you answered that.
But notice in the question example rascal used a filename output specification (for directory and file name), for example i can use:
$rostopic echo /fix>/home/user/directory/filename.txt
and it will write the messages in the specified directory, is there any way I can run the rostopic echo from a launch like the one you gave, but specifing also the output file directory? Personally I would like to output addicional messages with output="screen" and output topic messages in the .txt file specified in the directory
but im not able to find the way to output the file in a specified directory
Thank you very much,
Pablo Payno