Dears,
how to determine the commands that could be used by certain user..like I want to prevent some users from running pwd command????

Thanx

pwd being a shell builtin, you'll have a hard time disabling it outside patching the shell itself or building your own limited one.

I dont know how to patch the shell ?? is there any other way???

Maybe you can fool your users inserting in their environment these custom functions:

builtin() { echo "builtin is disabled"; }
unset() { echo "unset is disabled"; }
pwd() { echo "pwd is disabled"; }

For now I don't have any clever ideas

I guess the right solution is using an existing restricted shell (eg: rksh). I was just pointing "pwd" isn't a command easy to neutralize. robotronic functions should work though along with rksh which forbids the user to run the "cd" command, something certainly more useful than forbidding "pwd".

"man rksh" for details.