implementing loops in a c brainfuck interpreter

I have written a simple brainfuck interpreter in c. all the commands work fine, except for loops. currently, I am handeling them like this:

I have a function to find the matching square bracket:

int findbracket(char *commands, int currentpos){
    int lb = 0;
    int rb = 0;

    for(int i = currentpos; i != strlen(commands); ++i){
        if(commands[i] == '[') ++lb;
        if(commands[i] == ']') ++rb;

        if(lb == rb){
            return i;
        }
    }
}

and the I have a stack to keep track of all the brackets:

void interpret(char *commands){
    int stack[10];
    int top = 0;

    for(int i = 0; i < strlen(commands); ++i){
        char command = commands[i];
        
        //other commands...
        else if(command == '['){
            if(*ptr == 0){
                i = findbracket(commands, i);
            }
            else{
                stack[top] = i;
                ++top;
            }
        }
        else if(command == ']'){
            if(*ptr != 0){
                i = stack[top];
            }
            else{
                --top;
            }
        }
    }
}

however, this doesn't seem to work. for example, when executing hello world: ++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++. it gives no output at all. what am I doing wrong?

You want:

            if(*ptr != 0){
                i = stack[top-1];
            }

"top" marks where the next thing will go on the stack, just above where the last thing was added.