From b0c4969472a8a101a40631d124047dfb8df9c587 Mon Sep 17 00:00:00 2001
From: Steve Lee <slee@microsoft.com>
Date: Wed, 7 Jun 2017 13:37:43 -0700
Subject: [PATCH] when powershell is used in a shebang script
 (#!/usr/bin/powershell) without a ps1 extension, powershell treats it as a
 native command so this ends up in a recursive loop.  fix is to inspect the
 command to see if it is a shebang script and one we should handle.  if so,
 just treat it like a ps1 script.

---
 .../engine/CommandSearcher.cs                 | 36 ++++++++++++++++++-
 test/powershell/Host/ConsoleHost.Tests.ps1    | 12 +++++++
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/src/System.Management.Automation/engine/CommandSearcher.cs b/src/System.Management.Automation/engine/CommandSearcher.cs
index 65ac77eb577..142352aa98b 100644
--- a/src/System.Management.Automation/engine/CommandSearcher.cs
+++ b/src/System.Management.Automation/engine/CommandSearcher.cs
@@ -635,7 +635,41 @@ private CommandInfo GetInfoFromPath(string path)
                     break;
                 }
 
-                if (String.Equals(extension, StringLiterals.PowerShellScriptFileExtension, StringComparison.OrdinalIgnoreCase))
+                // handle case where we are called by the OS to handle a shebang script using us as the interpreter
+                bool isShebangScript = false;
+                try
+                {
+                    using(FileStream fileStream = new FileStream(path, FileMode.Open, FileAccess.Read))
+                    {
+                        byte[] bytes = new byte[2];
+                        int bytesRead = fileStream.Read(bytes, 0, 2);  // read the first two bytes to determine if shebang
+                        if (bytesRead == 2)
+                        {
+                            if (bytes[0] == '#' && bytes[1] == '!')
+                            {
+                                // see if we are supposed to be the interpreter
+                                using(StreamReader file = new StreamReader(fileStream))
+                                {
+                                    string interpreter = file.ReadLine();
+                                    System.Reflection.Assembly assembly = System.Reflection.Assembly.GetEntryAssembly();
+                                    // this returns path to powershell.dll
+                                    string powershellPath = assembly.Location.Replace(".dll","");
+                                    // need to handle both powershell and powershell.exe
+                                    if (interpreter.Split(' ',2)[0].Replace(".exe","") == powershellPath)
+                                    {
+                                        isShebangScript = true;
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+                catch(Exception)
+                {
+                    // If we can't read the file, safe to assume it's not a script
+                }
+
+                if (isShebangScript || String.Equals(extension, StringLiterals.PowerShellScriptFileExtension, StringComparison.OrdinalIgnoreCase) || isShebangScript)
                 {
                     if ((_commandTypes & CommandTypes.ExternalScript) != 0)
                     {
diff --git a/test/powershell/Host/ConsoleHost.Tests.ps1 b/test/powershell/Host/ConsoleHost.Tests.ps1
index 50dd8fb17df..bd0ac3a1960 100644
--- a/test/powershell/Host/ConsoleHost.Tests.ps1
+++ b/test/powershell/Host/ConsoleHost.Tests.ps1
@@ -176,6 +176,18 @@ Describe "ConsoleHost unit tests" -tags "Feature" {
             # no extraneous output
             $observed | should be $currentVersion
         }
+
+        $testCases =
+            @{interpreter = "#!${pshome}/powershell"},
+            @{interpreter = "#!${pshome}/powershell.exe"}
+
+        It "Should properly execute shebang script that doesn't have .ps1 extension" -TestCases $testCases {
+            param($Interpreter)
+            $scriptPath = "~/shebangtest"
+            Set-Content -Path $scriptPath -Value $Interpreter
+            Add-Content -Path $scriptPath -Value "'hello'"
+            & $powershell $scriptPath | Should BeExactly 'hello'
+        }
     }
 
     Context "Pipe to/from powershell" {