$ which cd
cd: dukesh built-in command
$ which echo
echo: dukesh built-in command
$ which pwd
pwd: dukesh built-in command
$ which which
which: dukesh built-in command
$ which ./bin/ls
./bin/ls
$ which ./bin/head
./bin/head
$ which ls
/usr/bin/ls
$ which head
/usr/bin/head
$ quit