Signal to stop a container.

Allow to set the signal to stop a container in `docker run`:
- Use `--stop-signal` with docker-run to set the default signal the container will use to exit.

Signed-off-by: David Calavera <david.calavera@gmail.com>

signal/signal.go

@@ -3,8 +3,12 @@
 package signal
 
 import (
+	"fmt"
 	"os"
 	"os/signal"
+	"strconv"
+	"strings"
+	"syscall"
 )
 
 // CatchAll catches all signals and relays them to the specified channel.
@@ -21,3 +25,20 @@ func StopCatch(sigc chan os.Signal) {
 	signal.Stop(sigc)
 	close(sigc)
 }
+
+// ParseSignal translates a string to a valid syscall signal.
+// It returns an error if the signal map doesn't include the given signal.
+func ParseSignal(rawSignal string) (syscall.Signal, error) {
+	s, err := strconv.Atoi(rawSignal)
+	if err == nil {
+		if s == 0 {
+			return -1, fmt.Errorf("Invalid signal: %s", rawSignal)
+		}
+		return syscall.Signal(s), nil
+	}
+	signal, ok := SignalMap[strings.TrimPrefix(strings.ToUpper(rawSignal), "SIG")]
+	if !ok {
+		return -1, fmt.Errorf("Invalid signal: %s", rawSignal)
+	}
+	return signal, nil
+}