I actually fixed this a couple of days ago (see here
<http://github.com/rikonor/stdio-wrapper>) without realizing what the issue
was, but now I understand! Thank you!
On Fri, Feb 9, 2018 at 10:27 PM Matt Harden <matt.har...@gmail.com> wrote:
> You need to close fIn after the copy is done. As it is now, fIn.Close()
> happens after io.Copy(os.Stdout, buf), which completes after your cat
> command finishes. But cat won't finish until its input pipe returns EOF,
> which happens after fIn.Close().
>
> On Wed, Feb 7, 2018 at 5:46 PM Or Rikon <riko...@gmail.com> wrote:
>
>> Hi!
>>
>> I asked this previously on Stack Overflow but so far have not received a
>> response, so I figured I will try here as well.
>>
>> I'm trying to wrap an executable that takes an input and output file
>> paths as arguments, such that it will be possible to provide the input and
>> output as stdin and stdout.
>>
>> I've written a short script in Go that attempts to do this, but for some
>> reason which eludes me, it hangs forever.
>>
>>
>> Here is the script:
>>
>>
>> package main
>> import (
>> "bytes"
>> "io"
>> "log"
>> "os"
>> "strings"
>> "syscall"
>>
>> "golang.org/x/sync/errgroup")
>> /*
>> Expected behavior:
>>
>> # Terminal 1
>> $ go run main.go
>>
>> # Terminal 2
>> $ cat inPipe > outPipe
>>
>> The go program is writing to inPipe and reading from outPipe
>>
>> Actual behavior: The program stalls
>> */
>>
>> func main() {
>> eg := &errgroup.Group{}
>>
>> inPipe := "inPipe"
>> outPipe := "outPipe"
>>
>> if err := syscall.Mkfifo(inPipe, 0644); err != nil {
>> log.Fatal(err)
>> }
>> defer os.Remove(inPipe)
>>
>> if err := syscall.Mkfifo(outPipe, 0644); err != nil {
>> log.Fatal(err)
>> }
>> defer os.Remove(outPipe)
>>
>> fIn, err := os.OpenFile(inPipe, os.O_WRONLY, os.ModeNamedPipe)
>> if err != nil {
>> log.Fatal(err)
>> }
>> defer fIn.Close()
>>
>> eg.Go(func() error {
>> _, err := io.Copy(fIn, strings.NewReader("123"))
>> return err
>> })
>>
>> fOut, err := os.OpenFile(outPipe, os.O_RDONLY, os.ModeNamedPipe)
>> if err != nil {
>> log.Fatal(err)
>> }
>> defer fOut.Close()
>>
>> buf := &bytes.Buffer{}
>>
>> eg.Go(func() error {
>> _, err := io.Copy(buf, fOut)
>> return err
>> })
>>
>> if err := eg.Wait(); err != nil {
>> log.Fatal(err)
>> }
>>
>> if _, err := io.Copy(os.Stdout, buf); err != nil {
>> log.Fatal(err)
>> }}
>>
>> --
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>
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