#
anything following a # to the end of the current line is treated as a comment and ignored
#!interpreter
if the first line of a script starts with this, then the script is run by the specified interpreter
rsh
running under the restricted shell is equivalent to ksh, except that the following is not allowed:
changing directories
setting value of ENV, PATH, or SHELL
specifying path or command names containing /
redirecting command output command with >, >|, <>, or >>
