You should probably investigate using the output of the which command
to get the path to the executable.
Be careful with 'which' :
145 -> man which
which(1) User Commands which(1)
NAME
which - locate a command; display its pathname or alias
....
BUGS
Only aliases and paths from ~/.cshrc are used; importing
from the current environment is not attempted. Must be exe-
cuted by csh(1), since only csh knows about aliases.
So, (1) if you call it from sh rather than csh, you may have problems.
(2) if you change your path after .cshrc runs, OR if you didn't even
run .cshrc, 'which' will give WRONG answers, since it temporarily
erases the $path and rebuilds it from your .cshrc.
I, personally, would not have listed this under BUGS--I would
introduce a new heading:
STUPIDITIES THAT MAKE IT OF LITTLE USE
If SHELL=ksh, consider 'whence'