The
shells file contains a list of the shells on the system. It can be used in conjunction with the Hesiod domain ‘shells', and the NIS map ‘shells', as controlled by
nsswitch.conf(5).
For each shell a single line should be present, consisting of the shell's path, relative to root.
A hash (“#”) indicates the beginning of a comment; subsequent characters up to the end of the line are not interpreted by the routines which search the file. Blank lines are also ignored.