TrueAbility - Linux Showdown 8 (Round 1) script.

#! /bin/bash
#
# You can find more info about this competition at following url:
# https://community.trueability.com/t/the-sub-par-assembler-round-1/911
#

#Main section.
spasm_dir_path="."
#spasm_dir_path="/var/lib/spasm"
print_error () {
  echo "Operation not supported or syntax error!"
}

#Check if there is any syntax error.
if ! [[ $(echo "$1" | grep -P "\b(mov|add|sub|mul|eq|lt|gt)\b") ]]; then
  print_error
  exit 1
elif ! [[ $(echo "$2" | grep -P "\bR(1|2|3|4)\b") ]]; then
  print_error
  exit 1
elif [[ ! $(echo "$3" | grep -P "(R(1|2|3|4)\b|%\b)") ]]; then
  print_error
  exit 1
fi

#Get target number.
target_number=$(cat ${spasm_dir_path}/$2 | grep -P -o "\d+")

#Get value number.
if [[ $(echo "$3" | grep -P "\bR(1|2|3|4)\b") ]]; then
  value_number=$(cat ${spasm_dir_path}/$3 | grep -P -o "\d+")
elif [[ $(echo "$3" | grep -P "%\b") ]]; then
  value_number=$(echo "$3" | grep -P -o "\d+")
fi

#Check Operations.
case $1 in
  mov)
  echo $value_number > ${spasm_dir_path}/$2
;;
  add)
  [[ -f ${spasm_dir_path}/$2 ]] && echo $(( $target_number + $value_number )) > ${spasm_dir_path}/$2 || print_error; exit 1
;;
  sub)
  [[ -f ${spasm_dir_path}/$2 ]] && echo $(( $target_number - $value_number )) > ${spasm_dir_path}/$2 || print_error; exit 1
;;
  mul)
  [[ -f ${spasm_dir_path}/$2 ]] && echo $(( $target_number * $value_number )) > ${spasm_dir_path}/$2 || print_error; exit 1
;;
  eq)
  [[ $target_number -eq $value_number ]] && echo -n "0" > ${spasm_dir_path}/CP || echo -n "1" > ${spasm_dir_path}/CP
;;
  lt)
  [[ $target_number -lt $value_number ]] && echo -n "0" > ${spasm_dir_path}/CP || echo -n "1" > ${spasm_dir_path}/CP
;;
  gt)
  [[ $target_number -gt $value_number ]] && echo -n "0" > ${spasm_dir_path}/CP || echo -n "1" > ${spasm_dir_path}/CP
;;
esac