In /usr/bin/showchar line 7:
        echo "Usage: `basename $0` Font-Name Char-Name" >&2
                     ^-----------^ SC2006: Use $(...) notation instead of legacy backticked `...`.
                               ^-- SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
        echo "Usage: $(basename "$0") Font-Name Char-Name" >&2


In /usr/bin/showchar line 30:
   ($2 from font $1 displayed on `date` by `basename $0` 1.00 (C) AJCD 1991)
                                 ^----^ SC2006: Use $(...) notation instead of legacy backticked `...`.
                                           ^-----------^ SC2006: Use $(...) notation instead of legacy backticked `...`.
                                                     ^-- SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
   ($2 from font $1 displayed on $(date) by $(basename "$0") 1.00 (C) AJCD 1991)

For more information:
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
  https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le...