현재 쉘 보기

$ env | grep SHELL
SHELL=... //로그인 쉘

$ echo $0
-bash

$ ps $$
  PID TTY      STAT   TIME COMMAND
23752 pts/0    Rs     0:00 -bash

$ ps -p $$
  PID TTY          TIME CMD
23752 pts/0    00:00:00 bash

$ sh

# echo $0
sh

# ps -p $$
  PID TTY          TIME CMD
24794 pts/0    00:00:00 sh

$ env | grep SHELL
SHELL=... //처음과 동일함. sh가 아님.