Added --add, --remove, and --list options to edit a list of processes in a configuration file. Implemented StoreConfiguration func to save changes back to a file. Changed version text.

main.go

@@ -37,6 +37,8 @@ import (
 
 // ErrPgrepNotFound occurs when pgrep program is not found.
 var ErrPgrepNotFound = errors.New("pgrep not found")
+var ErrNotFound = errors.New("process is not on list")
+var ErrIsOnList = errors.New("process is already on list")
 
 // Configuration holds a list of process names to be tracked and a listen address.
 type Configuration struct {
@@ -60,6 +62,20 @@ func LoadConfiguration(path string) (conf *Configuration, err error) {
 	return conf, nil
 }
 
+func StoreConfiguration(path string, conf *Configuration) (err error) {
+	config, err := json.Marshal(*conf)
+	if err != nil {
+		return err
+	}
+
+	err = ioutil.WriteFile(path, config, 0644)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
 // ProcessList is a map of processes' statuses.
 type ProcessList map[string]bool
 
@@ -113,23 +129,83 @@ func AreProcessesUp(processes *[]string) func(http.ResponseWriter, *http.Request
 	}
 }
 
-func version() {
-	fmt.Println("httpprocwatchd ver. 1.0")
-	fmt.Println("Copyright (c) 2021 Alexander \"Arav\" Andreev <me@arav.top>")
-	fmt.Println("This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.")
-    fmt.Println("This is free software, and you are welcome to redistribute it")
-    fmt.Println("under certain conditions; type `show c' for details.")
+func AddProcessToList(process string, conf *Configuration, configPath string) error {
+	for _, v := range conf.Processes {
+		if v == process {
+			return ErrIsOnList
+		}
+	}
+
+	conf.Processes = append(conf.Processes, process)
+	if err := StoreConfiguration(configPath, conf); err != nil {
+		return err
+	}
+
+	return nil
 }
 
+func RemoveProcessFromList(process string, conf *Configuration, configPath string) error {
+	for k, v := range conf.Processes {
+		if v == process {
+			copy(conf.Processes[:k], conf.Processes[k+1:])
+			
+			if err := StoreConfiguration(configPath, conf); err != nil {
+				return err
+			}
+
+			return nil
+		}
+	}
+
+	return ErrNotFound
+}
+
+func ListWatchedProcesses(processes *[]string) {
+	lastidx := len(*processes) - 1
+	for k, v := range *processes {
+		if k == lastidx {
+			fmt.Printf("%s\n", v)
+		} else {
+			fmt.Printf("%s, ", v)
+		}
+	}
+}
+
+func version() {
+	fmt.Println("httpprocwatchd ver. 1.1")
+	fmt.Println("Copyright (c) 2021 Alexander \"Arav\" Andreev <me@arav.top>")
+	fmt.Println("License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.")
+    fmt.Println("This is free software, and you are welcome to change and redistribute it.")
+    fmt.Println("There is NO WARRANTY, to the extent permitted by law.")
+}
+
+var oConfigPath string
+var oShowVersion bool
+var oListProcesses bool
+
+var oAddProcess string
+var oRemoveProcess string
+
 func main() {
 	log.SetFlags(0)
 
-	configPath := flag.String("config", "processes.json", "path to configuration file")
-	showVersion := flag.Bool("version", false, "show version")
+	flag.StringVar(&oConfigPath, "config", "processes.json", "path to configuration file")
+	flag.StringVar(&oConfigPath, "c", "processes.json", "path to configuration file (shorthand)")
+	flag.BoolVar(&oShowVersion, "version", false, "show version")
+	flag.BoolVar(&oShowVersion, "v", false, "show version (shorthand)")
+
+	flag.BoolVar(&oListProcesses, "list", false, "list watched processes")
+	flag.BoolVar(&oListProcesses, "l", false, "list watched processes (shorthand)")
+
+	flag.StringVar(&oAddProcess, "add", "", "add process to list")
+	flag.StringVar(&oAddProcess, "a", "", "add process to list (shorthand)")
+
+	flag.StringVar(&oRemoveProcess, "remove", "", "remove process from list")
+	flag.StringVar(&oRemoveProcess, "r", "", "remove process from list (shorthand)")
 
 	flag.Parse()
 
-	if *showVersion {
+	if oShowVersion {
 		version()
 		return
 	}
@@ -138,11 +214,31 @@ func main() {
 		log.Fatalln(ErrPgrepNotFound)
 	}
 
-	conf, err := LoadConfiguration(*configPath)
+	conf, err := LoadConfiguration(oConfigPath)
 	if err != nil {
 		log.Fatalf("Cannot load configuration file: %s\n", err)
 	}
 
+	if oListProcesses {
+		ListWatchedProcesses(&conf.Processes)
+		return
+	}
+
+	if oAddProcess != "" {
+		err := AddProcessToList(oAddProcess, conf, oConfigPath)
+		if err != nil {
+				log.Fatalf("Cannot add process: %s\n", err)
+		}
+		return
+	}
+
+	if oRemoveProcess != "" {
+		err := RemoveProcessFromList(oRemoveProcess, conf, oConfigPath)
+		if err != nil {
+				log.Fatalf("Cannot remove process: %s\n", err)
+		}
+		return
+	}
 	router := http.NewServeMux()
 	router.HandleFunc("/processes", AreProcessesUp(&conf.Processes))