Redirect stdin and out to sockets

gyula · #1 (**permalink**) 09-01-2008

For windows was pretty simple to redirect the std in a and out of a
child process for "cmd.exe " command prompt terminal to a socket using connected pipes passed to a new process in the STARTUPINFO structure.

Code:

 BOOL b = ::CreatePipe((LPHANDLE)h_stdInRead,(LPHANDLE)hsdtInWriteTmp, &SecAttrib, 0);
    b &= ::CreatePipe((LPHANDLE)hsdtOutReadTmp, (LPHANDLE)h_sdtOutWrite, &SecAttrib, 0);
    b &= ::DuplicateHandle(hProcess, hsdtInWriteTmp, hProcess, h_this2Write, 0, 0, DUPLICATE_SAME_ACCESS);
    b &= ::DuplicateHandle(hProcess, hsdtOutReadTmp, hProcess, h_this2Read, 0, 0, DUPLICATE_SAME_ACCESS);

    hsdtInWriteTmp.Close();
    hsdtOutReadTmp.Close();

    si.dwFlags      = 0;
    si.cb           = sizeof(STARTUPINFO);
    si.dwFlags      = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
    si.wShowWindow  = SW_HIDE;
    si.hStdInput    = h_stdInRead;
    si.hStdOutput   = h_sdtOutWrite;
    si.hStdError    = h_sdtOutWrite;
    si.wShowWindow    = SW_HIDE;
    si.lpDesktop    = 0;   
    si.lpTitle        = "blah" // Version();
   CreateProcess(NULL, "cmd.exe", lps, NULL, 1, CREATE_NEW_CONSOLE, NULL, NULL, psi, ppi) ;
/*
...
...
*/
//handles only 1 connection
 while(1)
{
  if(sock >0)
  {
  if(receive(socket, buffer))
    WriteFile(h_this2Write,..)
  if(ReadFile(h_this2Read))
     send(socket);
  }
  else
  {
     sock = wait_4_connection(); //accept and listen
  }

In above code the context (current directory) of the terminal cmd.exe is not lost between connections, and I can run internal shell commands as start, call, cd, and so on ....

For Linux I've tried to mimic the shell using popen(), and to write and read in the handler returned by popen(), but I cannot run /bash shell commands as cd, cp, mkdir and so on because they are internal bin/bash commands. I would like to have a shell up, and to write and read from it trough it's stdin stdout, available in my app (pipes of file handlers).
Something like:

Code:

//handles only 1 connection
   
  execl_and_get_sddin_and_out("bin/bash"); // keep it up
    ...   
  while(1)
  {
   if(sock >0)
  {
    if(receive(socket, buffer))
      fwrite(shell_stdin,..)
   if(fread(she__stdout))
      send(socket);
  }
  else
  {
     sock = wait_4_connection(); //accept and listen
  }
}

I tried these samples (but they don;t hold the shell up, and the command is sent to a shell, then the shell is closed):

Tying Standard Input and Output to a Socket Connection
http://src.gnu-darwin.org/DarwinSour...h/sshconnect.c

Does anyone has any idea how this can be accomplished.

Thank you.
Gyula.

otheus · #2 (**permalink**) 09-02-2008

Sorry, why are you creating a socket connection? Why don't you use pipe the output of the command back to the user?

Quote:

For Linux I've tried to mimic the shell using popen(), and to write and read in the handler returned by popen(), but I cannot run /bash shell commands as cd, cp, mkdir and so on because they are internal bin/bash commands

Hunh? If you use popen, the only limitation is that you cannot both read from and write into the file descriptor. Only if that limitation is a problem do you need sockets. But you say you can't run them because they are "internal commands". But there almost always external versions of these commands available. (For cd, however, it's useless -- you must do this within the context of your program, or prefix all subsequent commands with a "cd".) Regardless, all one needs to do in this case is run bash and provide it the command to parse.

Code:

fd=popen("/bin/bash -c \"cd /tmp; echo *\"","r");

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