F5 has multiple command line access:
From 11.x code version, F5 decided to focus future development only on tmsh. So, if you are trying to learn one of them, concentrate on tmsh. The cli is useful when we have to execute multiple commands within a short span of time like during a maintenance window.
Moving from TMSH to Bash:
root@lbal1(Active)(tmos)# run util bash
Moving from Bash to TMSH:
[root@lbal1:Active] log #tmsh
TMSH has the “(tmos)” in the prompt and the Bash CLI looks more like Linux prompt.