Pinvoke CreateProcess input/output from file

Question

I use code from example in this answer. It works.

But I need to redirect standart input/output into files. Process startup info struct has fields:

public IntPtr hStdInput;
public IntPtr hStdOutput;
public IntPtr hStdError;

I tried something like this:

StartupInfo startupInfo = new StartupInfo();
startupInfo.cb = Marshal.SizeOf((object)startupInfo);
startupInfo.dwFlags = 128;

FileStream fs = new FileStream(filePath, FileMode.Open);
startupInfo.hStdInput = fs.Handle;

And it does not work.

How can I pass file as standart input/output?

UPD1.

How do I call CreateProccess:

StartupInfo startupInfo = new StartupInfo();
startupInfo.cb = Marshal.SizeOf((object)startupInfo);
startupInfo.dwFlags = 128;

FileStream fs = new FileStream(filePath, FileMode.Open);
startupInfo.hStdInput = fs.Handle;

Pinvoke.SetErrorMode(ErrorModes.SEM_FAILCRITICALERRORS | ErrorModes.SEM_NOALIGNMENTFAULTEXCEPT | ErrorModes.SEM_NOGPFAULTERRORBOX | ErrorModes.SEM_NOOPENFILEERRORBOX);
CreationFlags dwCreationFlags = CreationFlags.CREATE_BREAKAWAY_FROM_JOB | CreationFlags.CREATE_SUSPENDED | CreationFlags.CREATE_SEPARATE_WOW_VDM;
SecurityAttributes securityAttributes = new SecurityAttributes();
securityAttributes.bInheritHandle = 1;
ProcessInformation pi;

if (!Pinvoke.CreateProcess(null, configuration.RunString, ref securityAttributes, ref securityAttributes, boolInheritHandles: true, dwCreationFlags: dwCreationFlags, lpEnvironment: IntPtr.Zero, lpszCurrentDir: configuration.Directory, startupInfo: ref startupInfo, pi: out pi))
    throw new Win32Exception(Marshal.GetLastWin32Error());

UPD2. I added SetHandleInformation call, but it does not help:

FileStream fs = new FileStream(@"C:\input.txt", FileMode.Open, FileAccess.Read);
Pinvoke.SetHandleInformation(fs.Handle, 0x00000001, 0x00000001);
startupInfo.hStdInput = fs.Handle;

file handles must be *inheritable* and process must be created with *bInheritHandles == true* — RbMm, Jun 18 '17 at 14:52
@RbMm thank you for your comment. I added true in `CreateProcess` call and in `securityAttributes`, but it does not help — Backs, Jun 18 '17 at 15:01
but you need use securityAttributes in create/open file handle - not process — RbMm, Jun 18 '17 at 15:03
`FileStream fs = new FileStream(filePath, FileMode.Open);` - this is `fs.Handle;` not inheritable handle — RbMm, Jun 18 '17 at 15:04
@RbMm ok, I see... It's difficult for me :) thank you for comments, I'll try! — Backs, Jun 18 '17 at 15:07
@DavidHeffernan or use [`SetHandleInformation()`](https://msdn.microsoft.com/en-us/library/windows/desktop/ms724935.aspx) to turn on the `HANDLE_FLAG_INHERIT` flag. — Remy Lebeau, Jun 18 '17 at 19:38
@RemyLebeau I added this call, but it does not help. Maybe, I do something wrong — Backs, Jun 19 '17 at 02:17
It's pointless to wrap the handle in a file stream. Not least because there is buffering at play. Call CreateFile. A classic mistake is to do this all from C# without having once learnt how to do it from C++ code. Easier to experiment in C++ code because all prototypes, constants etc. are available. Once you know how to do it, translate to pinvoke. — David Heffernan, Jun 19 '17 at 06:27
`#define STARTF_USESTDHANDLES 0x00000100` - this flag you must use in `STARTUPINFO` but you use `startupInfo.dwFlags = 128;` - `128==0x80!=0x100` — RbMm, Jun 19 '17 at 08:06
and better of course just create file as inheritable in single api call (via createfile) than do 2 system calls - first create file handle not inheritable and than change this — RbMm, Jun 19 '17 at 08:09
@RbMm yes, that's was is. You can turn this comment to answer, I'll accept it. — Backs, Jun 19 '17 at 08:25
@DavidHeffernan @RbMm thank you both for help. I'm really bad at wiapi and C++, but your comments give me right direction for search. I'll try to do it as you described: work with files with `CreateFile`. — Backs, Jun 19 '17 at 08:27

score 0 · Accepted Answer · answered Jun 21 '17 at 14:30

Based on comments.

Set startupInfo.dwFlags to 0x00000100

Add new function CreateFile:

[DllImport("kernel32.dll", SetLastError = true)]
public static extern IntPtr CreateFile(string lpFileName, DesiredAccess dwDesiredAccess, uint dwShareMode, ref SecurityAttributes lpSecurityAttributes, CreationDisposition dwCreationDisposition, uint dwFlagsAndAttributes, IntPtr hTemplateFile);

Create input/output handlers:

var input = Pinvoke.CreateFile(inputFile, DesiredAccess.GENERIC_READ, 0, ref securityAttributes,
            CreationDisposition.OPEN_EXISTING, 0, IntPtr.Zero);

var output = Pinvoke.CreateFile(outputFile, DesiredAccess.GENERIC_WRITE, 0, ref securityAttributes,
             CreationDisposition.CREATE_NEW, 0, IntPtr.Zero);

startupInfo.hStdInput = input;
startupInfo.hStdOutput = output;

...

public enum DesiredAccess : uint
{
    GENERIC_WRITE = 30,
    GENERIC_READ = 31
}

public enum CreationDisposition : uint
{
    CREATE_NEW = 1,
    CREATE_ALWAYS = 2,
    OPEN_EXISTING = 3,
    OPEN_ALWAYS = 4,
    TRUNCATE_EXISTING = 5
}

Pinvoke CreateProcess input/output from file

1 Answers1