eof

Builtin index · File I/O

result = eof(f)

Input: f · Output: result

What it is

Checks whether f (file handle, opened readable) has any bytes left to read from the current position.

Overloads

One call shape — this function is not overloaded.

Examples

From the documentation, and run by the build -- the output and the figure below are what the engine actually produced. Simplest first.

f = fopen("streaming_demo.txt", "w")
for i = 0 to 4
    write_line(f, "line " + str(i))
end for
close(f)

g = fopen("streaming_demo.txt", "r")
n = 0
while not eof(g)
    line = read_line(g)
    n = n + 1
end while
close(g)
print("lines read = {n}")

from tour

n = fopen("notes.txt", "w")
write_line(n, "line one")
write_line(n, "line two")
close(n)

function drain(s)
    total = ""
    while not eof(s)
        total = total + read_line(s) + "|"
    end while
    close(s)
    return total
end function

a = drain(StreamFile("notes.txt"))
print(a)                                    # line one|line two|


b = drain(StreamURL("https://example.com/"))
print(length(b) > 0)                        # true -- some HTML came back

line one|line two|
true

from file-io

function drain(s)
    total = ""
    while not eof(s)
        total = total + read_line(s) + "|"
    end while
    close(s)
    return total
end function

# Written here so the file half runs; the URL half cannot be, since a

# documentation build must not depend on the network being up or on a

# third party's page not changing under it.

w = fopen("stream_notes.txt", "w")
write_line(w, "one")
write_line(w, "two")
close(w)

a = drain(StreamFile("stream_notes.txt"))
b = drain(StreamURL("https://example.com/"))
print("a = {a}")
print("b length = {length(b)}")

from tour

How it works

§ file/directory I/O extensions + type casts (2026-08-26, keep this already-large match's diff footprint small while another pass concurrently edits this same file. See fs_ops::call's own doc comment for what each name does. eof(f) on a Value::UrlStream (from StreamURL) — see net_ops::stream_eof's own doc comment. Pulled out of the combined fs_ops arm just below (which only knows about Value::File) so eof dispatches across both stream kinds, the same "same method name, same behavior" polymorphism read_line/read_all/close above already give.

From the note above this builtin in the interpreter, where the reasoning was written down as it was built.