Golang File reader scopes mistake

Question

I'm trying to understand difference between two file-reading cases.

Code below works fine. We reading file line-by-line to the variable:

reader := bufio.NewReader(file)

var line string
for err != io.EOF {
    line, err = reader.ReadString('\n')
    log.Println(line)
}

But if I want to init (using reader) in for scope reader will infinitely read only first line of code:

reader := bufio.NewReader(file)

var line string
for line, err = reader.ReadString('\n'); err != io.EOF; {
    log.Println(line)
}

Please, explain me why it happens? Thanks

because you're performing read only in initialization block (which is run only once). Move it to the post statement as well. https://tour.golang.org/flowcontrol/1 — Kishore Bandi, Jul 15 '20 at 14:04
Welcome. posted the same answer. You can close the question. — Kishore Bandi, Jul 15 '20 at 14:09

score 0 · Accepted Answer · answered Jul 15 '20 at 14:08

0

Move it from initialization (Which runs only once) to post-statement. Change it to

for line, err = reader.ReadString('\n'); err != io.EOF; line, err = reader.ReadString('\n') {
    log.Println(line)
}

answered Jul 15 '20 at 14:08

Kishore Bandi

Maybe it's not the best decision (we have repeated code) but I could see true difference. Thank you. It solves my problem – Anatol' Jul 15 '20 at 14:14

1 Answers1