How to pass STDIN to child process? - c++

Question

void WriteToPipe(void)
// Read from a file and write its contents to the pipe for the child's STDIN.
// Stop when there is no more data.
{
DWORD dwRead, dwWritten;
CHAR chBuf[BUFSIZE];
BOOL bSuccess = FALSE;
char * name = malloc(100);
fgets(name, 100, stdin);
bSuccess = WriteFile(g_hChildStd_IN_Wr, name, 10, &dwWritten, NULL);
if (!bSuccess)
ErrorExit("");
}
void ReadFromPipe(void)
// Read output from the child process's pipe for STDOUT
// and write to the parent process's pipe for STDOUT.
// Stop when there is no more data.
{
DWORD dwRead, dwWritten;
CHAR chBuf[BUFSIZE];
BOOL bSuccess = FALSE;
HANDLE hParentStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
bSuccess = ReadFile(g_hChildStd_OUT_Rd, chBuf, BUFSIZE, &dwRead, NULL);
if (!bSuccess || dwRead == 0)
return 100;
bSuccess = WriteFile(hParentStdOut, chBuf,
dwRead, &dwWritten, NULL);
if (!bSuccess)
return 101;
}
The main (not full):
while (1)
{
Sleep(500);
ReadFromPipe();
WriteToPipe();
}
I am trying to open the cmd as a child process and to pass the parent input to the child STDIN stream, and than to print the STDOUT of the child.
As you can see, it works at the first time but then I get this "more?" back from the child process (the cmd) and then it gets stuck waiting for output.
Why am I getting this "more?" back?
What is that "more?"

Answer 1

The only way of the redirection of parent input which I found - is creation an additional thread. The common algorithm is:
Create pipe - (hPipeRead, hPipeWrite)
Create child process with standard input - hPipeRead
Create new thread in parent process that is reading GetStdHandle(STD_INPUT_HANDLE) and is writing read buffer to hPipeWrite immediately. Thread is completed when stdInput is over.
Parent process is waiting additional thread
This way is described in Microsoft support article.