feat: allow logging to stdout, stderr

changelog/unreleased/pull-217

@@ -0,0 +1,13 @@
+Feature: Log to stdout using the `--log -` option
+
+Logging to stdout was possible using `--log /dev/stdout`. However,
+when the rest server is run as a different user, for example, using
+
+	`sudo -u restic rest-server [...] --log /dev/stdout`
+
+this did not work due to permission issues.
+
+For logging to stdout, the `--log` option now supports the special
+filename `-` which also works in these cases.
+
+https://github.com/restic/rest-server/pull/217

cmd/rest-server/main.go

@@ -46,7 +46,7 @@ func init() {
 	flags.StringVar(&cpuProfile, "cpu-profile", cpuProfile, "write CPU profile to file")
 	flags.BoolVar(&server.Debug, "debug", server.Debug, "output debug messages")
 	flags.StringVar(&server.Listen, "listen", server.Listen, "listen address")
-	flags.StringVar(&server.Log, "log", server.Log, "write HTTP requests in the combined log format to the specified `filename`")
+	flags.StringVar(&server.Log, "log", server.Log, "write HTTP requests in the combined log format to the specified `filename` (use \"-\" for logging to stdout)")
 	flags.Int64Var(&server.MaxRepoSize, "max-size", server.MaxRepoSize, "the maximum size of the repository in bytes")
 	flags.StringVar(&server.Path, "path", server.Path, "data directory")
 	flags.BoolVar(&server.TLS, "tls", server.TLS, "turn on TLS support")

mux.go

@@ -2,6 +2,7 @@ package restserver
 
 import (
 	"fmt"
+	"io"
 	"log"
 	"net/http"
 	"os"
@@ -21,9 +22,16 @@ func (s *Server) debugHandler(next http.Handler) http.Handler {
 }
 
 func (s *Server) logHandler(next http.Handler) http.Handler {
-	accessLog, err := os.OpenFile(s.Log, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
-	if err != nil {
-		log.Fatalf("error: %v", err)
+	var accessLog io.Writer
+
+	if s.Log == "-" {
+		accessLog = os.Stdout
+	} else {
+		var err error
+		accessLog, err = os.OpenFile(s.Log, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
+		if err != nil {
+			log.Fatalf("error: %v", err)
+		}
 	}
 
 	return handlers.CombinedLoggingHandler(accessLog, next)