How can I tell if I'm in a child shell

Question

If I'm using bash and type bash I'm in the child shell and need to type exit to go back to the original parent shell. If I forget which one I'm in how do I check?

Answer 1

Use the SHLVL environment variable.

man bash:

SHLVL : Incremented by one each time an instance of bash is started.

$ echo "$SHLV"
1

$ bash

$ echo "$SHLV"
2

$ exit

$ echo "$SHLV"
1