cmd: Add pidfile support (closes #3235)

cmd/commandfuncs.go

@@ -41,6 +41,7 @@ import (
 func cmdStart(fl Flags) (int, error) {
 	startCmdConfigFlag := fl.String("config")
 	startCmdConfigAdapterFlag := fl.String("adapter")
+	startCmdPidfileFlag := fl.String("pidfile")
 	startCmdWatchFlag := fl.Bool("watch")
 
 	// open a listener to which the child process will connect when
@@ -71,6 +72,9 @@ func cmdStart(fl Flags) (int, error) {
 	if startCmdWatchFlag {
 		cmd.Args = append(cmd.Args, "--watch")
 	}
+	if startCmdPidfileFlag != "" {
+		cmd.Args = append(cmd.Args, "--pidfile", startCmdPidfileFlag)
+	}
 	stdinpipe, err := cmd.StdinPipe()
 	if err != nil {
 		return caddy.ExitCodeFailedStartup,
@@ -149,6 +153,7 @@ func cmdRun(fl Flags) (int, error) {
 	runCmdResumeFlag := fl.Bool("resume")
 	runCmdPrintEnvFlag := fl.Bool("environ")
 	runCmdWatchFlag := fl.Bool("watch")
+	runCmdPidfileFlag := fl.String("pidfile")
 	runCmdPingbackFlag := fl.String("pingback")
 
 	// if we are supposed to print the environment, do that first
@@ -225,6 +230,16 @@ func cmdRun(fl Flags) (int, error) {
 		go watchConfigFile(configFile, runCmdConfigAdapterFlag)
 	}
 
+	// create pidfile
+	if runCmdPidfileFlag != "" {
+		err := caddy.PIDFile(runCmdPidfileFlag)
+		if err != nil {
+			caddy.Log().Error("unable to write PID file",
+				zap.String("pidfile", runCmdPidfileFlag),
+				zap.Error(err))
+		}
+	}
+
 	// warn if the environment does not provide enough information about the disk
 	hasXDG := os.Getenv("XDG_DATA_HOME") != "" &&
 		os.Getenv("XDG_CONFIG_HOME") != "" &&