Add support to pass env vars to in addition to args to configure cmk

Author: vishesh92

README.md

@@ -79,6 +79,27 @@ If cloudmonkey is being upgraded from a version lower than v6.0.0, it must be no
 that the cloudmonkey configuration path is changed from `~/.cloudmonkey/config` to 
 `~/.cmk/config` and a default `localcloud` profile is created. One must first set up basic configurations such as apikey/secretkey/username/password/url for the required profile(s) as required
 
+### Environment Variables
+
+`cmk` supports environment variables that mirror its CLI flags. CLI flags take
+precedence over environment variables, which take precedence over values in the
+config file.
+
+| Environment variable | Flag | Description |
+|----------------------|------|-------------|
+| `CMK_CONFIG` | `-c` | Config file path |
+| `CMK_PROFILE` | `-p` | Server profile |
+| `CMK_URL` | `-u` | CloudStack's API endpoint URL |
+| `CMK_API_KEY` | `-k` | CloudStack user's API key |
+| `CMK_SECRET_KEY` | `-s` | CloudStack user's secret key |
+| `CMK_OUTPUT` | `-o` | API response output format |
+| `CMK_DEBUG` | `-d` | Enable debug mode when set to `true` or `1` |
+
+`CMK_CONFIG` must point to an existing config file, and `CMK_PROFILE` must name
+an existing profile in the config; otherwise `cmk` exits with an error. A profile
+selected via `CMK_PROFILE` applies only to that invocation and is not persisted
+to the config file.
+
 ### License
 
 Licensed to the Apache Software Foundation (ASF) under one

cmd/command.go

@@ -65,13 +65,15 @@ CloudMonkey (cmk) 🐵 is a command line interface for Apache CloudStack.
 Allowed flags:
   -h        Show this help message or API doc when specified after an API
   -v        Print version
-  -o        API response output format: json, text, table, column, csv
-  -p        Server profile
-  -d        Enable debug mode
-  -c        Different config file path
-  -u	    CloudStack's API endpoint URL
-  -s	    CloudStack user's secret Key
-  -k	    CloudStack user's API Key
+  -o        API response output format: json, text, table, column, csv (env: CMK_OUTPUT)
+  -p        Server profile (env: CMK_PROFILE)
+  -d        Enable debug mode (env: CMK_DEBUG)
+  -c        Different config file path (env: CMK_CONFIG)
+  -u	    CloudStack's API endpoint URL (env: CMK_URL)
+  -s	    CloudStack user's secret Key (env: CMK_SECRET_KEY)
+  -k	    CloudStack user's API Key (env: CMK_API_KEY)
+
+CLI flags take precedence over their environment variables.
 
 Default commands:
 %s

cmk.go

@@ -53,6 +53,34 @@ func main() {
 	flag.Parse()
 	args := flag.Args()
 
+	// Fall back to environment variables for flags not passed on the
+	// command line; CLI flags take precedence over environment variables.
+	if *configFilePath == "" {
+		*configFilePath = os.Getenv(config.ConfigFileEnvVar)
+	}
+	if *profile == "" {
+		*profile = os.Getenv(config.ProfileEnvVar)
+	}
+	if *acsURL == config.DefaultACSAPIEndpoint {
+		if value := os.Getenv(config.URLEnvVar); value != "" {
+			*acsURL = value
+		}
+	}
+	if *apiKey == "" {
+		*apiKey = os.Getenv(config.APIKeyEnvVar)
+	}
+	if *secretKey == "" {
+		*secretKey = os.Getenv(config.SecretKeyEnvVar)
+	}
+	if *outputFormat == "" {
+		*outputFormat = os.Getenv(config.OutputEnvVar)
+	}
+	if !*debug {
+		if value := os.Getenv(config.DebugEnvVar); value == "true" || value == "1" {
+			*debug = true
+		}
+	}
+
 	cfg := config.NewConfig(configFilePath)
 
 	if *showVersion {

config/config.go

@@ -56,6 +56,24 @@ var nonEmptyConfigKeys = map[string]bool{
 // DefaultACSAPIEndpoint is the default API endpoint for CloudStack.
 const DefaultACSAPIEndpoint = "http://localhost:8080/client/api"
 
+// Environment variables that mirror CLI flags; flags take precedence.
+const (
+	// ConfigFileEnvVar sets the config file path when -c is not passed
+	ConfigFileEnvVar = "CMK_CONFIG"
+	// ProfileEnvVar sets the server profile when -p is not passed
+	ProfileEnvVar = "CMK_PROFILE"
+	// URLEnvVar sets CloudStack's API endpoint URL when -u is not passed
+	URLEnvVar = "CMK_URL"
+	// APIKeyEnvVar sets CloudStack user's API key when -k is not passed
+	APIKeyEnvVar = "CMK_API_KEY"
+	// SecretKeyEnvVar sets CloudStack user's secret key when -s is not passed
+	SecretKeyEnvVar = "CMK_SECRET_KEY"
+	// OutputEnvVar sets the API response output format when -o is not passed
+	OutputEnvVar = "CMK_OUTPUT"
+	// DebugEnvVar enables debug mode when set to true or 1 and -d is not passed
+	DebugEnvVar = "CMK_DEBUG"
+)
+
 // ServerProfile describes a management server
 type ServerProfile struct {
 	URL       string       `ini:"url"`
@@ -435,7 +453,7 @@ func NewConfig(configFilePath *string) *Config {
 	if *configFilePath != "" {
 		defaultConf.ConfigFile, _ = filepath.Abs(*configFilePath)
 		if _, err := os.Stat(defaultConf.ConfigFile); os.IsNotExist(err) {
-			fmt.Println("Config file doesn't exist.")
+			fmt.Printf("Config file '%s' doesn't exist.\n", defaultConf.ConfigFile)
 			os.Exit(1)
 		}
 	}