There is no program called "echo". Output into a shell is provided by a shell function called "echo", so you would always get a "can't run program" error if you try to invoke it.
What are you trying to output, where are you trying to output it, and why? When I need to output anything, I tend to use the testExec class in a JSR-223 step, as it can output to log files and to the test execution results. Various examples of the use of this class can be found in DevTest 8.0 - Scripting Guide - V1.1.pdf