Checking available shell and shell depth

□ Checking Available shells : cat /etc/shells
□ Environment variable for recording depth of shell : SHLVL(=SHell LeVeL)


ps.

1. Checking Shell depth : env | grpe SH
2. SHLVL = 1 is a state that only login-shell is executed
3. Based on Ubuntu

It is also posted at : cysecguide.blogspot.com/2016/08/checking-available-shell-and-shell-depth.html