4.6.8 Reading the State of Opened Streams

Byte, character, line count and line position for a specified stream are obtained as follows:

• byte_count(Stream, N) unifies N with the total number of bytes either read or written on the open binary stream Stream.
• character_count(Stream, N) unifies N with the total number of characters either read or written on the open text stream Stream.
• line_count(Stream, N) unifies N with the total number of lines either read or written on the open text stream Stream. A freshly opened text stream has a line count of 0, i.e. this predicate counts the number of newlines seen.
• line_position(Stream, N) unifies N with the total number of characters either read or written on the current line of the open text stream Stream. A fresh line has a line position of 0, i.e. this predicate counts the length of the current line.