gistfile1.c

void execute_command(char command, FILE *input){
	char c;
	long pos;

	switch(command) {
	case '>':
		++p;
		if(!*p)
			++last_p;
		break;
	case '<':
		--p;
		break;
	case '+':
		++*p;
		break;
	case '-':
		--*p;
		break;
	case '.':
		*curr_c = *p;
		++curr_c;
		++last_c;
		break;
	case ',':
		printf("Enter a character: ");
		*p = getchar();
		break;
	case '[':
		if ((*p) == 0) {
			int loopc = 0;
			for(;;)
			{
				c = getc(input);
				if (loopc == 0 && c == ']') break;
				if (c == ']') loopc--;
				if (c == '[') loopc++;
			}
		}else{
			break;
		}
	case ']':
		if((*p) != 0){
			pos = ftell(input)-1;
			int loopc = 0;
			for(;;)
			{
				fseek(input, --pos, SEEK_SET);
				c = getc(input);
				if (loopc == 0 && c == '[') break;
				if (c == ']') loopc++;
				if (c == '[') loopc--;
			}
		}else{
			break;
		}
	}
}