What is it?

You can use this small ocaml library to detect the dimensions of the terminal window attached to a process. It contains the two following functions:

val get_rows : unit -> int option
val get_columns : unit -> int option

How does it work?

Usually, to get this information, one would open a pipe from tput cols or stty size and parsing the output. Instead, this uses the ioctl that these commands use, TIOCGWINSZ.