Bash convert string to integer
I am new at bash scripting, I need to write a script capable of taking a file with a given text (written numbers and arithmetic operators) and transform these words into integers and ex: +, -, *, %.
The example that I have is a file with the following text : one two three plus nine eight seven. The script needs to change these words and transform them to 123 + 987, then printing the result 1110.
So far I have this, but I am not sure how to compare each word in the file to the ones in my code with the correct values to be able to do the operations.
#!/bin/bash
fileCal="$1" #file in_calc is entered
d=( ["zero"]="0" ["one"]="1" ["two"]="2" ["three"]"3" ["four"]="4"
["five"]"5" ["six"]="6" ["seven"]="7" ["eight"]="8" ["nine"]="9" ["plus"]="+" ["minus"]="-"
["times"]="\*" ["div"]="/" ["modulo"]="%")
if [ "$#" == 0 ]; then echo $error
elif [ -f $fileCal ]; then read -a $fileCal
fi
