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We are running a system which has our Linux & Unix Boxes authenticate against AD and because we have numerous different versions of Unix/Linux, we have to default to /bin/sh to make sure that the logins always work no matter the Server. I am looking to setup a .profile on RHEL to check to see what shell is set to at login and if its not bash, to switch to bash. I am not having any luck google searching for a method to do this and my shell scripting is on the weaker side.
How does one check for shell and switch at login without the control of the passwd file?