wingetty.c

#define WIN32_LEAN_AND_MEAN
#include <stdio.h>
#include <windows.h>

int main(int argc, char *argv[])
{
    char devname[MAX_PATH] = "\\\\.\\";
    HANDLE serial;
    BOOL ret;
    PROCESS_INFORMATION pi;
    DCB dcb = {
        .DCBlength = sizeof(DCB),
        .BaudRate = CBR_115200,
        .ByteSize = 8,
        .Parity = NOPARITY,
        .StopBits = ONESTOPBIT,
    };

    if (argc != 2) {
        puts("no device supplied");
        return 1;
    }

    if (strlen(devname) + strlen(argv[1]) > MAX_PATH) {
        puts("invalid device");
        return 1;
    }

    strcat(devname, argv[1]);

    serial = CreateFile(devname, GENERIC_READ | GENERIC_WRITE, 0, NULL,
                    OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

    if (serial == INVALID_HANDLE_VALUE) {
        puts("CreateFile() failed");
        return 1;
    }
    SetCommState(serial, &dcb);

    /* Method 1: via STARTUPINFO.hStd{Input,Output,Error} */
    STARTUPINFO si = {
        .cb = sizeof(si),
        .dwFlags = STARTF_USESTDHANDLES,
        .hStdInput = serial,
        .hStdOutput = serial,
        .hStdError = serial,
    }

    ret = CreateProcess(NULL, "cmd.exe", NULL, NULL, FALSE,
                HIGH_PRIORITY_CLASS, NULL, "C:\\", &si, &pi);

    /* Method 2: via handle inheritance */
    if (!SetStdHandle(STD_INPUT_HANDLE, serial)) {
        puts("SetStdHandle(STD_INPUT_HANDLE) failed");
        return 1;
    }
    if (!SetStdHandle(STD_OUTPUT_HANDLE, serial)) {
        puts("SetStdHandle(STD_OUTPUT_HANDLE) failed");
        return 1;
    }
    if (!SetStdHandle(STD_ERROR_HANDLE, serial)) {
        puts("SetStdHandle(STD_ERROR_HANDLE) failed");
        return 1;
    }

    ret = CreateProcess(NULL, "cmd.exe", NULL, NULL, TRUE,
                HIGH_PRIORITY_CLASS, NULL, "C:\\", &si, &pi);

    if (!ret) {
        puts("CreateProcess() failed");
        return 1;
    }

    return 0;
}