go/src/bufio: fmt.Print files differently for windows/amd64 and linux/amd64

[msmarino]

What version of Go are you using (go version)?

$ go version
go1.12.1 windows/amd64

>ver

Microsoft Windows [Versión 10.0.17134.590]

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\tecop\AppData\Local\go-build
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOOS=windows
set GOPATH=D:\Documents\Dev\Go
set GOPROXY=
set GORACE=
set GOROOT=C:\Go
set GOTMPDIR=
set GOTOOLDIR=C:\Go\pkg\tool\windows_amd64
set GCCGO=gccgo
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=D:\Documents\Dev\term\go.mod
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\tecop\AppData\Local\Temp\go-build251247510=/tmp/go-build -gno-record-gcc-switches

What did you do?

package main

import (
	"bufio"
	"fmt"
	"io"
	"log"
	"os/exec"
	"time"
)

func main() {
	cmd := exec.Command("bash")

	in, _ := cmd.StdinPipe()
	out, _ := cmd.StdoutPipe()

	if err := cmd.Start(); err != nil {
		log.Fatal(err)
	}

	go func() {
		reader := bufio.NewReader(out)
		for {
			s, err := reader.ReadString('\n')
			if err != nil {
				fmt.Print("Done!")
				return
			}
			// log.Print(s)
			fmt.Print(s)
		}
	}()

	io.WriteString(in, "ls -lha\n")

	io.WriteString(in, "exit\n")

	time.Sleep(2 * time.Second)

	cmd.Wait()
}

What did you expect to see?

Output from go version
go1.12.1 linux/amd64

total 4.0K
drwxrwxrwx 1 marcos marcos 4.0K Mar 16 09:54 .
drwxrwxrwx 1 marcos marcos 4.0K Mar 15 22:28 ..
drwxrwxrwx 1 marcos marcos 4.0K Mar 15 22:48 .git
-rwxrwxrwx 1 marcos marcos   46 Mar 15 22:34 go.mod
-rwxrwxrwx 1 marcos marcos  576 Mar 16 09:46 main.go
Done!

What did you see instead?

total 4.0Ktotal 4.0K
drwxrwxrwx 1 marcos marcos 4.0K Mar 16 09:54 .drwxrwxrwx 1 marcos marcos 4.0K Mar 16 09:54 .
drwxrwxrwx 1 marcos marcos 4.0K Mar 15 22:28 ..drwxrwxrwx 1 marcos marcos 4.0K Mar 15 22:28 ..
drwxrwxrwx 1 marcos marcos 4.0K Mar 15 22:48 .gitdrwxrwxrwx 1 marcos marcos 4.0K Mar 15 22:48 .git
-rwxrwxrwx 1 marcos marcos   46 Mar 15 22:34 go.mod-rwxrwxrwx 1 marcos marcos   46 Mar 15 22:34 go.mod
-rwxrwxrwx 1 marcos marcos  576 Mar 16 09:46 main.go-rwxrwxrwx 1 marcos marcos  576 Mar 16 09:46 main.go
Done!

Sometimes some lines are output correctly and others not.
log.Print seem to always output correctly on Windows

[katiehockman]

Looking at the expected vs. the actual output, I'm not sure that this is actually a bug, or just a difference in formatting depending on the OS that the program is being run against.

/cc @bradfitz @ianlancetaylor ?

[bradfitz]

I'm guessing that on Windows you probably have some '\r' bytes in there from bash messing up the output. This isn't really a Go issue, though. Try removing them before printing.