UNIX for Dummies Questions & Answers

I am practicing making my own functions in bash for an upcoming exam. For this example, I want to print out a message and maybe add two numbers. What I would do then is:

Code:

bash-3.2$ function practice
{
#code to print
#code to add
}

This would be run using an input file, that would contain such example information:

print hello
2 + 3

So, since "print" isn't how you print in UNIX, I would need to somehow transform this into echo. I could use sed to go through the file and replace every instance of "print" with echo, correct?

For 2 + 3, I am having some issues figuring this out. I don't know the order of the file that I will be inputting, for example, it could be:

2 + 4
5 + 8
8 - 3
print whats up
print hey
3 + 1
print lol

So I cannot hardcode field values using bc! I have to make my code be able to roll with the punches, I guess. Is there a way I can insert bc at the beginning of each line, or is that even the way it should be done?

Changing the input file isn't the way to go. What you need to do is read the input and interpret the contents acting on what you read. The psuedo code might be something like this:

Code:

function add
   echo $1 + $2

function sub
   echo $1 - $2

function printit
   echo $@

while read line from file
do
   case token_1 in 
        digit)   
             if token_2 is + 
                 call add token_1 token_3
             else if token_2 is -
                 call sub token_1 token_3
             end

        'print')   call printit tokens[2-n]

        quit)    exit
   end
done

Hopes this gets started.