Constantly feeds user input to given command and displays output

feeder.bash

#!/bin/bash

# feeder script
# Constantly feeds user input to given command and displays output

fullStr=""

while true; do

    read -n 1 -s nextChar

    # Check if character is backspace
    hexChar="$(echo $nextChar | hexdump)"
    if [[ "$hexChar" =~ .*0a7f.* ]]; then
        if [[ fullStr = "" ]]; then
            # If the string is empty, exit the program
            exit
        else
            # Otherwise, remove last character
            fullStr="${fullStr:0:-1}"
        fi
    elif [[ "$hexChar" =~ .*000a.* ]]; then
        # Space character entered
        fullStr="$fullStr "
    else
        # If not backspace, add character to string
        fullStr="$fullStr$nextChar"
    fi

    clear

    termHeight="$(stty size | cut -d' ' -f1)"
    termHeight="$(($termHeight - 6))"

    echo "$@ $fullStr"
    echo "----------------------------------------------------"

    # Run command
    echo "$($@ $fullStr | head -$termHeight)"

done