This message indicates that the Bourne shell could not find the program name given as a command.
Check the form and spelling of the command line. If that looks correct, echo $PATH to see if the user's search path is correct. When communications are garbled, it is possible to unset a search path to such an extent that only built-in shell commands are available. Here is a command to reset a basic search path:
$ PATH=/usr/bin:/usr/ccs/bin:/usr/openwin/bin:. |