In /usr/bin/showfigfonts line 13:
DIR=`dirname $0`
    ^----------^ SC2006: Use $(...) notation instead of legacy backticked `...`.
             ^-- SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
DIR=$(dirname "$0")


In /usr/bin/showfigfonts line 17:
FIGLETVERSION=`$FIGLET -I1 2>/dev/null`
              ^-----------------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
FIGLETVERSION=$($FIGLET -I1 2>/dev/null)


In /usr/bin/showfigfonts line 22:
USAGE="Usage: `basename $0` [ -d directory ] [ word ]"
              ^-----------^ SC2006: Use $(...) notation instead of legacy backticked `...`.
                        ^-- SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
USAGE="Usage: $(basename "$0") [ -d directory ] [ word ]"


In /usr/bin/showfigfonts line 39:
    FONTDIR="`$FIGLET -F | sed -e '1d' -e '3,$d' -e 's/Font directory: //'`"
             ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
    FONTDIR="$($FIGLET -F | sed -e '1d' -e '3,$d' -e 's/Font directory: //')"


In /usr/bin/showfigfonts line 42:
    FONTDIR="`$FIGLET -I2`"
             ^-----------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
    FONTDIR="$($FIGLET -I2)"


In /usr/bin/showfigfonts line 46:
FONTLIST=`ls "$FONTDIR"/*.flf | sed 's!.*/\(.*\)\.flf$!\1!'`
         ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.
          ^-----------------^ SC2012: Use find instead of ls to better handle non-alphanumeric filenames.

Did you mean: 
FONTLIST=$(ls "$FONTDIR"/*.flf | sed 's!.*/\(.*\)\.flf$!\1!')

For more information:
  https://www.shellcheck.net/wiki/SC2012 -- Use find instead of ls to better ...
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
  https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le...