feat(arguments): Arguments can now be passed as environment variables.

The following flags have an equivalent environment variable:
- a : FALCOSIDEKICK_UI_ADDR
- p : FALCOSIDEKICK_UI_PORT
- r : FALCOSIDEKICK_UI_REDIS_URL
- x : FALCOSIDEKICK_UI_DEV

The precedence order is:
- Command line flag
- Environment
- Default Value

Signed-off-by: Lyonel Martinez <[email protected]>

README.md

@@ -13,16 +13,17 @@ Events are stored in a `Redis` server with [`Redisearch`](https://github.com/Red
 ## Usage
 
 ### Options
+#### Precedence: flag value -> environment variable value -> default value
 
 ```shell
   -a string
-        Listen Address (default "0.0.0.0")
+        Listen Address (default "0.0.0.0", environment "FALCOSIDEKICK_UI_ADDR")
   -d    Enable dark mode as default
   -p int
-        Listen Port (default 2802)
+        Listen Port (default 2802, environment "FALCOSIDEKICK_UI_PORT")
   -r string
-        Redis server address (default "localhost:6379")
-  -x    Allow CORS for development
+        Redis server address (default "localhost:6379", environment "FALCOSIDEKICK_UI_REDIS_URL")
+  -x    Allow CORS for development (environment "FALCOSIDEKICK_UI_DEV")
 ```
 
 ### Run with docker

internal/utils/utils.go

@@ -1,8 +1,10 @@
 package utils
 
 import (
+	"flag"
 	"fmt"
 	"log"
+	"os"
 	"regexp"
 	"sort"
 	"strconv"
@@ -77,3 +79,16 @@ func RemoveDuplicate(input []string) []string {
 	sort.Strings(singleKeys)
 	return singleKeys
 }
+
+func GetFlagOrEnvParam(flagString string, envVar string, defaultValue string, usage string) *string {
+	res := flag.String(flagString, "NON-SET", usage)
+	if *res == "NON-SET" {
+		str, present := os.LookupEnv(envVar)
+		if present {
+			*res = str
+		} else {
+			*res = defaultValue
+		}
+	}
+	return res
+}

main.go

@@ -6,6 +6,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"strconv"
 
 	"github.com/falcosecurity/falcosidekick-ui/configuration"
 	"github.com/falcosecurity/falcosidekick-ui/internal/api"
@@ -34,12 +35,20 @@ type CustomValidator struct {
 }
 
 func init() {
-	addr := flag.String("a", "0.0.0.0", "Listen Address")
-	port := flag.Int("p", 2802, "Listen Port")
+	addr := utils.GetFlagOrEnvParam("a", "FALCOSIDEKICK_UI_ADDR", "0.0.0.0", "Listen Address")
+	portString := utils.GetFlagOrEnvParam("p", "FALCOSIDEKICK_UI_PORT", "2802", "Listen Port")
+	port, err := strconv.Atoi(*portString)
+	if err != nil {
+		utils.WriteLog("error", "Failed to parse Listen Port", true)
+	}
+	redisserver := utils.GetFlagOrEnvParam("r", "FALCOSIDEKICK_UI_REDIS_URL", "localhost:6379", "Redis server address")
+	dev := flag.Bool("x", false, "Allow CORS for development")
+	if !*dev {
+		_, *dev = os.LookupEnv("FALCOSIDEKICK_UI_DEV")
+	}
+
 	// darkmod := flag.Bool("d", false, "Enable dark mode as default")
 	version := flag.Bool("v", false, "Print version")
-	dev := flag.Bool("x", false, "Allow CORS for development")
-	redisserver := flag.String("r", "localhost:6379", "Redis server address")
 	flag.Parse()
 
 	if *version {
@@ -54,7 +63,7 @@ func init() {
 		utils.WriteLog("error", "Failed to parse Listen Address", true)
 	}
 	config.ListenAddress = *addr
-	config.ListenPort = *port
+	config.ListenPort = port
 	// config.DisplayMode = light
 	// if *darkmod {
 	// 	config.DisplayMode = dark