Just go through the manual page of useradd command. As per menual:
-s, --shell SHELL
The name of the user's login shell. The default is to leave this field blank, which causes the system to select the default login shell specified by the SHELL variable in /etc/default/useradd, or an empty string by default.
Thus, with other command line options, you can use -s
option to specify user's default shell. Moroever, you can use separately use the chsh
command to change user's shell (this option may not be available in all Unix variant).
# chsh [-s shell] [username]