In /usr/bin/nroff line 34:
case "`exec 2>/dev/null ; locale charmap`" in
      ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
case "$(exec 2>/dev/null ; locale charmap)" in


In /usr/bin/nroff line 68:
for i
^-^ SC2034: i appears unused. Verify use (or export if used externally).


In /usr/bin/nroff line 136:
PATH="$GROFF_RUNTIME$PATH" groff -mtty-char $T $opts ${1+"$@"}
                                               ^---^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
PATH="$GROFF_RUNTIME$PATH" groff -mtty-char $T "$opts" ${1+"$@"}

For more information:
  https://www.shellcheck.net/wiki/SC2034 -- i appears unused. Verify use (or ...
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
  https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le...