ctr: move shim to commands

Signed-off-by: Jess Valarezo <valarezo.jessica@gmail.com>

cmd/ctr/commands/shim/io_unix.go

@@ -0,0 +1,68 @@
+// +build !windows
+
+package shim
+
+import (
+	gocontext "context"
+	"io"
+	"os"
+	"sync"
+
+	"github.com/containerd/fifo"
+	"golang.org/x/sys/unix"
+)
+
+func prepareStdio(stdin, stdout, stderr string, console bool) (wg *sync.WaitGroup, err error) {
+	wg = &sync.WaitGroup{}
+	ctx := gocontext.Background()
+
+	f, err := fifo.OpenFifo(ctx, stdin, unix.O_WRONLY|unix.O_CREAT|unix.O_NONBLOCK, 0700)
+	if err != nil {
+		return nil, err
+	}
+	defer func(c io.Closer) {
+		if err != nil {
+			c.Close()
+		}
+	}(f)
+	go func(w io.WriteCloser) {
+		io.Copy(w, os.Stdin)
+		w.Close()
+	}(f)
+
+	f, err = fifo.OpenFifo(ctx, stdout, unix.O_RDONLY|unix.O_CREAT|unix.O_NONBLOCK, 0700)
+	if err != nil {
+		return nil, err
+	}
+	defer func(c io.Closer) {
+		if err != nil {
+			c.Close()
+		}
+	}(f)
+	wg.Add(1)
+	go func(r io.ReadCloser) {
+		io.Copy(os.Stdout, r)
+		r.Close()
+		wg.Done()
+	}(f)
+
+	f, err = fifo.OpenFifo(ctx, stderr, unix.O_RDONLY|unix.O_CREAT|unix.O_NONBLOCK, 0700)
+	if err != nil {
+		return nil, err
+	}
+	defer func(c io.Closer) {
+		if err != nil {
+			c.Close()
+		}
+	}(f)
+	if !console {
+		wg.Add(1)
+		go func(r io.ReadCloser) {
+			io.Copy(os.Stderr, r)
+			r.Close()
+			wg.Done()
+		}(f)
+	}
+
+	return wg, nil
+}