Recently, an automatic patch update of OSX Yosemite 10.10 made my terminal window not understand any bash commands, e.g.
*********
Last login: Fri Sep 25 18:46:40 on ttys000
test-mac:~ test$ ls
-bash: ls: command not found
test-mac:~ test$ vi
-bash: vi: command not found
test-mac:~ test$
*********
I tried the solution suggested in stackexchange, and that did the trick!:
$export PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin