Unknown size of array in assembly 8086

I need to get a string input from user but i don't know the size of the string he would enter and i need to prepare an array in the memory as the size of the string because I'm using the interrupt 21h, ah=0ah. So my question is how to get an input of string if I don't know the size of it? Is there any other interrupt I can use? I searched but I didn't find anything.

Solution

I suggest you create a buffer with a fixed size and use a loop with the interrupt 21h, ah=8 for direct character input.

That way you can check how many bytes the user enters and terminate if this number exceeds your buffer size.

In short:

create a buffer with a sufficient size
grab a single char until
- it is a linebreak
- the number of entered chars will exceed your buffer
do not forget to zero terminate your string

And if you really need to read the whole string you can maybe find a way to reallocate your buffer dynamically.