Thru CL how can I display a message on the message line?
Which “message line”? A message line for a system display? A message line occupied by a message subfile? A message line for some other program that calls your CL?
And what kind of message? Is it an error message that should persist after your CL completes or is it a status message that is transient and exists only while your CL is actually running?
There are many variations for different uses within different environments. You need to describe the scenario. Describe programs in the call stack and point out which programs control message lines.