Linux® users are often surprised to find that Bash is not the default shell in FreeBSD. In fact, Bash is not included in the default installation. Instead, FreeBSD uses tcsh(1) as the default root shell, and the Bourne shell-compatible sh(1) as the default user shell. sh(1) is very similar to Bash but with a much smaller feature-set. Generally shell scripts written for sh(1) will run in Bash, but the reverse is not always true.
However, Bash and other shells are available for installation using the FreeBSD Packages and Ports Collection.
After installing another shell, use chsh(1) to change
      a user's default shell.  It is recommended that the
      root user's default
      shell remain unchanged since shells which are not included in
      the base distribution are installed to
      /usr/local/bin.  In the event of a problem,
      the file system where /usr/local/bin is
      located may not be mounted.  In this case, root would not have access to
      its default  shell, preventing root from logging in and fixing
      the problem.
All FreeBSD documents are available for download at https://download.freebsd.org/ftp/doc/
Questions that are not answered by the
    documentation may be
    sent to <freebsd-questions@FreeBSD.org>.
    Send questions about this document to <freebsd-doc@FreeBSD.org>.