Obtains the total number of characters either input from or output to the current line of the open text stream Stream and unifies it with Count.
A valid open text stream.
The resulting line count of the stream.
A fresh line has a line position of 0, i.e. this predicate counts the length of the current line. Line count for an interactive stream reflects the total line input from or output to any interactive stream, i.e. all interactive streams share the same counter.
The count is reset by
Stream errors (see ref-iou-sfh-est).