as Rick said. To elaborate: What 'chmod u+x' does (for some scripts it might be safer to use 'a+x', so that not only the owner of the file but anyone - including the root user - can execute it) is to set the 'executable' bit on the shell script file, so that it can be executed. Alternatively, the shell 'sh' can be executed, with the file name as parameter (the 'sh' program is in the default PATH, so no explicit path (./ in the btup case) is needed, and it already has the 'x' bit set)

(That was today's little generic Unix/Linux lession..)