No Shell

win32 API

Create Processes

• CreateProcessW

File Association

• Use ShellExecuteEx  or ShellExecuteW , to open files by association (e.g., foo.pdf  with Acrobat).

• CreateProcess  does not handle file associations.

UAC Elevation

• CreateProcessW  runs with the caller’s token. It will not trigger UAC elevation.

• To elevate use ShellExecuteEx  with runas  or use CreateProcessWithTokenW  / CreateProcessAsUser  with the right token.

"Conveniences" you lose by not using a shell

• Built-ins :

  • Will not run dir , cd , or other cmd.exe  built-ins. Those are implemented inside the shell.

• .bat / .ps1 files :

  • *.bat , *.cmd , .ps1  are not native executables.

  • *.bat  must be run by cmd.exe cmd.exe /c yourscript.bat  (or use the shell).

  • *.ps1  must be run by PowerShell (or invoked via pwsh -File ).

• Pipes :

  • This refers to the usage of something like:

    • >

      • cmd.exe: Redirect stdout to a file (overwrite).

      • powershell: Redirect stdout to a file (overwrite).

    • |

      • cmd.exe: byte-stream pipe.

      • powershell: object pipeline.

  • You must create pipes yourself and wire STARTUPINFO.hStdInput / hStdOutput  and bInheritHandles .

  • You control the environment block and current directory. If you want inherited handles or specific stdio redirection you must set those in STARTUPINFO  and use bInheritHandles .

  • Odin does this with the win32  api by:

  &win32.STARTUPINFOW{
      cb = size_of(win32.STARTUPINFOW),
      hStdError  = stderr_handle,
      hStdOutput = stdout_handle,
      hStdInput  = stdin_handle,
      dwFlags = win32.STARTF_USESTDHANDLES,
  },
  

• Conditionals :

  • This refers to the usage of something like:

    • ||

      • cmd.exe: run RHS if LHS fails.

      • powershell: run RHS if LHS fails.

    • &&

      • cmd.exe: run RHS if LHS success.

      • powershell: run RHS if LHS success.

  • Parent or shell must implement conditional logic. Parent must check exit code and decide.

• Sequence invoke :

  • This refers to the usage of something like:

    • &

      • cmd.exe: Command operator. Runs next command unconditionally.

    • ;

      • powershell: Command operator.

  • If you want sequencing invoke multiple CreateProcessW  calls or implement sequencing logic in your program.