tlog: switch default logger to syslog

...unless "-nosyslog" is passed.

All gocryptfs messages already go to syslog, but the messages
that the go-fuse lib emits were still printed to stdout.

Fixes issue #13 ( https://github.com/rfjakob/gocryptfs/issues/13 )

internal/tlog/log_go1.4.go

@@ -8,5 +8,9 @@ import (
 )
 
 func (l *toggledLogger) SwitchToSyslog(p syslog.Priority) {
-	Debug.Printf("Cannot switch to syslog - need Go 1.5 or higher")
+	Info.Printf("Cannot switch to syslog - need Go 1.5 or higher")
+}
+
+func SwitchLoggerToSyslog(p syslog.Priority) {
+	Info.Printf("Cannot switch to syslog - need Go 1.5 or higher")
 }

internal/tlog/log_go1.5.go

@@ -4,14 +4,26 @@
 package tlog
 
 import (
+	"log"
 	"log/syslog"
 )
 
 func (l *toggledLogger) SwitchToSyslog(p syslog.Priority) {
 	w, err := syslog.New(p, ProgramName)
 	if err != nil {
-		Warn.Printf("Cannot switch 0x%02x to syslog: %v", p, err)
+		Warn.Printf("SwitchToSyslog: %v", err)
 	} else {
 		l.SetOutput(w)
 	}
 }
+
+// SwitchLoggerToSyslog redirects the default log.Logger that the go-fuse lib uses
+// to syslog.
+func SwitchLoggerToSyslog(p syslog.Priority) {
+	w, err := syslog.New(p, ProgramName)
+	if err != nil {
+		Warn.Printf("SwitchLoggerToSyslog: %v", err)
+	} else {
+		log.SetOutput(w)
+	}
+}

main.go

@@ -347,6 +347,7 @@ func main() {
 			tlog.Info.SwitchToSyslog(syslog.LOG_USER | syslog.LOG_INFO)
 			tlog.Debug.SwitchToSyslog(syslog.LOG_USER | syslog.LOG_DEBUG)
 			tlog.Warn.SwitchToSyslog(syslog.LOG_USER | syslog.LOG_WARNING)
+			tlog.SwitchLoggerToSyslog(syslog.LOG_USER | syslog.LOG_WARNING)
 		}
 	}
 	// Wait for SIGINT in the background and unmount ourselves if we get it.