System.Environment F# snippets

snippets/fsharp/System/Environment+SpecialFolder/Overview/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="getfolderpath.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/Environment+SpecialFolder/Overview/getfolderpath.fs

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+//<snippet1>
+// Sample for the Environment.GetFolderPath method
+open System
+
+printfn $"\nGetFolderPath: {Environment.GetFolderPath Environment.SpecialFolder.System}"
+
+// This example produces the following results:
+//     GetFolderPath: C:\WINNT\System32
+//</snippet1>

snippets/fsharp/System/Environment/CommandLine/commandline.fs

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+//<snippet1>
+open System
+
+//  Invoke this sample with an arbitrary set of command line arguments.
+printfn $"\nCommandLine: {Environment.CommandLine}"
+// The example displays output like the following:
+//       C:\>env0 ARBITRARY TEXT
+//
+//       CommandLine: env0 ARBITRARY TEXT
+//</snippet1>

snippets/fsharp/System/Environment/CommandLine/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="commandline.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/Environment/CurrentDirectory/Vars1.fs

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+//<Snippet4>
+open System
+open System.IO
+
+if Environment.OSVersion.Platform = PlatformID.Win32NT then
+    // Change the directory to %WINDIR%
+    Environment.CurrentDirectory <- Environment.GetEnvironmentVariable "windir"
+
+    let info = DirectoryInfo "."
+
+    printfn $"Directory Info:   {info.FullName}"
+else
+    printfn "This example runs on Windows only."
+// The example displays output like the following on a .NET implementation running on Windows:
+//        Directory Info:   C:\windows
+// The example displays the following output on a .NET implementation on Unix-based systems:
+//        This example runs on Windows only.
+//</Snippet4>

snippets/fsharp/System/Environment/CurrentDirectory/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Vars1.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/Environment/ExitCode/double.fs

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+module double
+
+// <Snippet1>
+open System
+open System.Numerics
+
+let ERROR_BAD_ARGUMENTS = 0xA0
+let ERROR_ARITHMETIC_OVERFLOW = 0x216
+let ERROR_INVALID_COMMAND_LINE = 0x667
+
+let args = Environment.GetCommandLineArgs()
+if args.Length = 1 then
+    Environment.ExitCode <- ERROR_INVALID_COMMAND_LINE
+else
+    match BigInteger.TryParse args[1] with
+    | true, value ->
+        if value <= bigint Int32.MinValue || value >= bigint Int32.MaxValue then
+            Environment.ExitCode <- ERROR_ARITHMETIC_OVERFLOW
+        else
+            printfn $"Result: {value * 2I}"
+    | _ ->
+        Environment.ExitCode <- ERROR_BAD_ARGUMENTS
+// </Snippet1>

snippets/fsharp/System/Environment/ExitCode/double1.fs

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+module double1
+
+// <Snippet2>
+open System
+open System.Numerics
+
+let ERROR_SUCCESS = 0
+let ERROR_BAD_ARGUMENTS = 0xA0
+let ERROR_ARITHMETIC_OVERFLOW = 0x216
+let ERROR_INVALID_COMMAND_LINE = 0x667
+
+[<EntryPoint>]
+let main _ =
+    let args = Environment.GetCommandLineArgs()
+    if args.Length = 1 then
+        ERROR_INVALID_COMMAND_LINE
+    else
+        match BigInteger.TryParse args[1] with
+        | true, value ->
+            if value <= bigint Int32.MinValue || value >= bigint Int32.MaxValue then
+                ERROR_ARITHMETIC_OVERFLOW
+            else
+                printfn $"Result: {value * 2I}"
+                ERROR_SUCCESS
+        | _ ->
+            ERROR_BAD_ARGUMENTS
+// </Snippet2>

snippets/fsharp/System/Environment/ExitCode/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="double.fs" />
+    <Compile Include="double1.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/Environment/ExpandEnvironmentVariables/expandenvironmentvariables.fs

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+//<snippet1>
+// Sample for the Environment.ExpandEnvironmentVariables method
+open System
+
+let nl = Environment.NewLine
+
+//  <-- Keep this information secure! -->
+let query = "My system drive is %SystemDrive% and my system root is %SystemRoot%"
+let str = Environment.ExpandEnvironmentVariables query
+printfn $"\nExpandEnvironmentVariables: {nl}  {str}"
+
+// This example produces the following results:
+//     ExpandEnvironmentVariables:
+//       My system drive is C: and my system root is C:\WINNT
+//</snippet1>

snippets/fsharp/System/Environment/ExpandEnvironmentVariables/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="expandenvironmentvariables.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/Environment/FailFast/ff.fs

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+//<snippet1>
+open System
+
+let causeOfFailure = "A catastrophic failure has occurred."
+
+// Assume your application has failed catastrophically and must
+// terminate immediately. The try-finally block is not executed
+// and is included only to demonstrate that instructions within
+// try-catch blocks and finalizers are not performed.
+try
+    Environment.FailFast causeOfFailure
+finally
+    printfn "This finally block will not be executed."
+
+// The example produces no output because the application is terminated.
+// However, an entry is made in the Windows Application event log, and
+// the log entry contains the text from the causeOfFailure variable.
+//</snippet1>

snippets/fsharp/System/Environment/FailFast/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="ff.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/Environment/GetCommandLineArgs/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="getcommandlineargs.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/Environment/GetCommandLineArgs/getcommandlineargs.fs

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+//<snippet1>
+open System
+
+//  Invoke this sample with an arbitrary set of command line arguments.
+let arguments = Environment.GetCommandLineArgs()
+
+String.concat ", " arguments
+|> printfn "\nGetCommandLineArgs: %s"
+
+// This example produces output like the following:
+//     C:\>GetCommandLineArgs ARBITRARY TEXT
+//
+//       GetCommandLineArgs: GetCommandLineArgs, ARBITRARY, TEXT
+// </snippet1>

snippets/fsharp/System/Environment/GetEnvironmentVariable/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="getenvironmentvariableex1.fs" />
+    <Compile Include="gsev.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/Environment/GetEnvironmentVariable/getenvironmentvariableex1.fs

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+module Example
+
+open System
+
+let mutable toDelete = false
+
+// Check whether the environment variable exists.
+let value = 
+    let v = Environment.GetEnvironmentVariable "Test1"
+    // If necessary, create it.
+    if isNull v then
+        Environment.SetEnvironmentVariable("Test1", "Value1")
+        toDelete <- true
+        Environment.GetEnvironmentVariable "Test1"
+    else 
+        v
+
+// Display the value.
+printfn $"Test1: {value}\n"
+
+// Confirm that the value can only be retrieved from the process
+// environment block if running on a Windows system.
+if Environment.OSVersion.Platform = PlatformID.Win32NT then
+    printfn "Attempting to retrieve Test1 from:"
+    for enumValue in Enum.GetValues typeof<EnvironmentVariableTarget> do
+        let value = Environment.GetEnvironmentVariable("Test1", enumValue :?> EnvironmentVariableTarget)
+        printfn $"""   {enumValue}: {if value <> null then "found" else "not found"}"""
+    printfn ""
+
+// If we've created it, now delete it.
+if toDelete then
+    Environment.SetEnvironmentVariable("Test1", null)
+    // Confirm the deletion.
+    if Environment.GetEnvironmentVariable "Test1" |> isNull then
+        printfn "Test1 has been deleted."
+// The example displays the following output if run on a Windows system:
+//      Test1: Value1
+//
+//      Attempting to retrieve Test1 from:
+//         Process: found
+//         User: not found
+//         Machine: not found
+//
+//      Test1 has been deleted.
+//
+// The example displays the following output if run on a Unix-based system:
+//      Test1: Value1
+//
+//      Test1 has been deleted.