在循环中进入bufio ReadString是无限的

Question

I have the next code:

resp, err := http.Get("https://www.google.com")

if err != nil{
    panic(err)
}

r := bufio.NewReader(resp.Body)

for v, e := r.ReadString('
'); e == nil; {
    fmt.Println(v)
}

So, I want to read responce body in loop but reader r reads first line of Body infinitely.

While in the same time, this code works fine:

v, e := r.ReadString('
')
for e == nil {
    fmt.Println(v)
    v, e = r.ReadString('
')
}

Can someone explain why the first solution has such behaviour?

Answer 1

Structure of the loop is:

for init; condition; post { }

The init part of the loop is called only once, at the beginning. That means that the...

v, e := r.ReadString('
')

...part from your loop is called only once, which explains why your loop implementation reads only the first line from r and why e is always nil, resulting in an infinite loop.

---

You may want to do something like this instead:

for v, e := "", (error)(nil); e == nil; {
    v, e = r.ReadString('
')
    fmt.Println(v)
}

Or if that looks weird to you, something like this:

var v string
var e error
for ; e == nil; {
    v, e = r.ReadString('
')
    fmt.Println(v)
}

More info here:

• https://golang.org/doc/effective_go.html#for
• https://golang.org/ref/spec#For_statements