add config element to load environment variables from a file

doc/xmlConfigFile.md

@@ -139,6 +139,14 @@ This optional element can be specified multiple times if necessary to specify en
 <env name="HOME" value="c:\abc" />
 ```
 
+### Environment File
+
+This optional element can be specified one time to specify a file to load environment variables from. Each variable definition must be on a separate line and in the format "key=value". Empty lines an lines starting with "#" are ignored. The syntax is:
+
+```xml
+<envFile>%BASE%/env.txt</env-file>
+```
+
 ### interactive
 
 If this optional element is specified, the service will be allowed to interact with the desktop, such as by showing a new window and dialog boxes. 

doc/yamlConfigFile.md

@@ -171,6 +171,14 @@ env:
         value: host1;host2
 ```
 
+### Environment File
+
+This optional element can be specified one time to specify a file to load environment variables from. Each variable definition must be on a separate line and in the format "key=value". Empty lines an lines starting with "#" are ignored. The syntax is:
+
+```yaml
+envFile: '%BASE%/env.txt'
+```
+
 ### interactive
 
 If this optional element is specified, the service will be allowed to interact with the desktop, such as by showing a new window and dialog boxes. 

src/WinSW.Core/Configuration/DefaultSettings.cs

@@ -129,6 +129,8 @@ namespace WinSW.Configuration
 
         public Dictionary<string, string> EnvironmentVariables => new(0);
 
+        public string? EnvironmentVariablesFile => null;
+
         // Misc
         public bool BeepOnShutdown => false;
 

src/WinSW.Core/Configuration/XmlServiceConfig.cs

@@ -65,6 +65,8 @@ namespace WinSW
             // Also inject system environment variables
             Environment.SetEnvironmentVariable(WinSWSystem.EnvVarNameServiceId, this.Name);
 
+            this.LoadEnvironmentVariablesFromFile();
+
             this.environmentVariables = this.LoadEnvironmentVariables();
         }
 
@@ -528,6 +530,11 @@ namespace WinSW
         /// </summary>
         public Dictionary<string, string> EnvironmentVariables => new(this.environmentVariables);
 
+        /// <summary>
+        /// File from which environment variables are loaded.
+        /// </summary>
+        public string? EnvironmentVariablesFile => this.SingleElement("envFile", optional: true);
+
         /// <summary>
         /// List of downloads to be performed by the wrapper before starting
         /// a service.
@@ -690,6 +697,18 @@ namespace WinSW
             return environment;
         }
 
+        private void LoadEnvironmentVariablesFromFile()
+        {
+            var envFile = this.SingleElement("envFile", optional: true);
+
+            if (envFile is null)
+            {
+                return;
+            }
+
+            ConfigHelper.LoadEnvironmentVariablesFile(envFile);
+        }
+
         public List<YamlExtensionConfig>? YamlExtensions => Defaults.YamlExtensions;
     }
 }

src/WinSW.Core/Configuration/YamlServiceConfig.cs

@@ -43,6 +43,8 @@ namespace WinSW.Configuration
             // Also inject system environment variables
             Environment.SetEnvironmentVariable(WinSWSystem.EnvVarNameServiceId, this.Name);
 
+            this.LoadEnvironmentVariablesFromFile();
+
             this.LoadEnvironmentVariables();
         }
 
@@ -201,6 +203,8 @@ namespace WinSW.Configuration
 
         public Dictionary<string, string> EnvironmentVariables { get; set; } = new Dictionary<string, string>();
 
+        public string? EnvironmentVariablesFile => Expand(this.raw.EnvFile) ?? this.defaults.EnvironmentVariablesFile;
+
         public void LoadEnvironmentVariables()
         {
             if (this.raw.Env is null)
@@ -224,6 +228,18 @@ namespace WinSW.Configuration
             }
         }
 
+        private void LoadEnvironmentVariablesFromFile()
+        {
+            string? envFile = Expand(this.raw.EnvFile);
+
+            if (envFile is null)
+            {
+                return;
+            }
+
+            ConfigHelper.LoadEnvironmentVariablesFile(envFile);
+        }
+
         public ServiceAccount ServiceAccount
         {
             get
@@ -315,6 +331,7 @@ namespace WinSW.Configuration
             public string? Priority;
             public string? BeepOnShutdown;
             public List<RawYamlEnv>? Env;
+            public string? EnvFile;
             public List<RawYamlFailureAction>? OnFailure;
             public string? DelayedAutoStart;
             public string? SecurityDescriptor;

src/WinSW.Core/Util/ConfigHelper.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 
 namespace WinSW.Util
 {
@@ -45,5 +46,29 @@ namespace WinSW.Util
 
             return false;
         }
+
+        public static void LoadEnvironmentVariablesFile(string envFile)
+        {
+            foreach (string line in File.ReadAllLines(envFile))
+            {
+                if (line.Length == 0 || line.StartsWith("#"))
+                {
+                    // ignore empty lines and comments
+                    continue;
+                }
+
+                int equalsSignIndex = line.IndexOf("=");
+
+                if (equalsSignIndex == -1)
+                {
+                    throw new WinSWException("The environment variables file (env-file) contains one or more invalid entries. Each variable definition must be on a separate line and in the format \"key=value\".");
+                }
+
+                string key = line.Substring(0, equalsSignIndex);
+                string value = line.Substring(equalsSignIndex + 1);
+
+                Environment.SetEnvironmentVariable(key, value);
+            }
+        }
     }
 }