read_string/3

Availability:built-in

read_string(+Stream, ?Length, -String)

Read at most Length characters from Stream and return them in the string String. If Length is unbound, Stream is read to the end and Length is unified with the number of characters read. Note that characters must be read as Unicode code points, not bytes.

Examples

Read all lines to a list

file_lines(File, Lines) :-
    setup_call_cleanup(open(File, read, In),
       stream_lines(In, Lines),
       close(In)).

stream_lines(In, Lines) :-
    read_string(In, _, Str),
    split_string(Str, "\n", "", Lines).

This loads all lines to memory as strings. If we use the Unix dictionary words:

?- file_lines("/usr/share/dict/words", Lines).
Words = ["A", "a", "aa", "aal", "aalii", "aam", "Aani", "aardvark", "aardwolf"|...].