Run a bash command until diff between two files is non-empty

Question

I have a two versions of a program, say : normalProgram and bruteProgram.

I have an input generator for both of these : programGenerator

Now I want to do this:

• Put the output of ./programGenerator into input.txt : ./programGenerator > input.txt
• Redirect input.txt as the input of normalProgram : cat input.txt | ./normalProgram
  • Put the output of ./normalProgram into op1.txt : (cat input.txt | ./normalProgram) > op1.txt
• Similar thing for ./bruteProgram :
  • (cat input.txt | ./bruteProgram) > op2.txt
• Now I want to compare op1.txt and op2.txt : diff op1.txt op2.txt

The whole command will look like this:

./programGenerator > input.txt &&
(cat input.txt | ./normalProgram) > op1.txt &&
(cat input.txt | ./bruteProgram) > op2.txt &&
diff op1.txt op2.txt

So this is a one time command.

I want to run this until diff op1.txt op2.txt gives a non-empty response.

I tried putting diff op1.txt op2.txt as the condition for until (or while, just to check whether the conditional is correct)

But this didn't work, and I got an error that, that is not a correct conditional.

Example:

while [diff normalOp.txt bruteOp.txt]
do
echo "hello"
done

This is giving me the error:

zsh: bad pattern: [diff

Answer 1

I just had to remove the square brackets from the condition:

while diff normalOp.txt bruteOp.txt  
do
echo "hello"
done

And this started working.

---

The exact bash command in this case would be:

while diff op1.txt op2.txt
while> do
while> ./programGenerator > input.txt   
while> (cat input.txt | ./normalProgram) > op1.txt
while> (cat input.txt | ./bruteProgram) > op2.txt
while> done