POSIX says: SHELL This variable shall represent a pathname of the user's preferred command language interpreter. If this interpreter does not conform to the Shell Command Language in XCU Chapter 2 (on page 2345), utilities may behave differently from those described in POSIX.1-2017.
There is no requirement to match one of the /etc/shells pathnames. The user or scripts should be free to use any arbitrary pathname to the command language interpreter available on the system, and Debian should ensure that this is allowed, in particular the one give by the realpath command. -- Vincent Lefèvre <vinc...@vinc17.net> - Web: <https://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)