Simple command line app to switch display modes on Windows via a CLI.

DisplayConfig.c

#include <windows.h>

LONG DisplayConfigSetDisplayMode(DISPLAYCONFIG_PATH_INFO *pPath, PDEVMODEW pDevMode, DWORD dwFlags)
{
    DISPLAYCONFIG_SOURCE_DEVICE_NAME dcSourceDeviceName = {.header = {.type = DISPLAYCONFIG_DEVICE_INFO_GET_SOURCE_NAME,
                                                                      .size = sizeof(DISPLAYCONFIG_SOURCE_DEVICE_NAME),
                                                                      .adapterId = pPath->sourceInfo.adapterId,
                                                                      .id = pPath->sourceInfo.id}};
    DisplayConfigGetDeviceInfo(&dcSourceDeviceName.header);

    return ChangeDisplaySettingsExW(dcSourceDeviceName.viewGdiDeviceName, pDevMode, NULL, dwFlags, NULL);
}

VOID DisplayConfigOutputDisplayName(DISPLAYCONFIG_PATH_INFO *pPath)
{
    DISPLAYCONFIG_SOURCE_DEVICE_NAME dcSourceDeviceName = {.header = {.type = DISPLAYCONFIG_DEVICE_INFO_GET_SOURCE_NAME,
                                                                      .size = sizeof(DISPLAYCONFIG_SOURCE_DEVICE_NAME),
                                                                      .adapterId = pPath->sourceInfo.adapterId,
                                                                      .id = pPath->sourceInfo.id}};
    DisplayConfigGetDeviceInfo(&dcSourceDeviceName.header);

    DISPLAYCONFIG_TARGET_DEVICE_NAME dcTargetDeviceName = {.header = {.type = DISPLAYCONFIG_DEVICE_INFO_GET_TARGET_NAME,
                                                                      .size = sizeof(DISPLAYCONFIG_TARGET_DEVICE_NAME),
                                                                      .adapterId = pPath->targetInfo.adapterId,
                                                                      .id = pPath->targetInfo.id}};
    DisplayConfigGetDeviceInfo(&dcTargetDeviceName.header);

    __builtin_printf("%ls\n", dcTargetDeviceName.flags.friendlyNameFromEdid
                                  ? dcTargetDeviceName.monitorFriendlyDeviceName
                                  : dcSourceDeviceName.viewGdiDeviceName);
}

VOID DisplayConfigOutputDisplayModes(DISPLAYCONFIG_PATH_INFO *pPath)
{
    DISPLAYCONFIG_SOURCE_DEVICE_NAME dcSourceDeviceName = {.header = {.type = DISPLAYCONFIG_DEVICE_INFO_GET_SOURCE_NAME,
                                                                      .size = sizeof(DISPLAYCONFIG_SOURCE_DEVICE_NAME),
                                                                      .adapterId = pPath->sourceInfo.adapterId,
                                                                      .id = pPath->sourceInfo.id}};
    DisplayConfigGetDeviceInfo(&dcSourceDeviceName.header);

    DEVMODEW dm = {.dmSize = sizeof(DEVMODEW)};
    DWORD iModeNum = 0;

    while (EnumDisplaySettingsW(dcSourceDeviceName.viewGdiDeviceName, iModeNum, &dm))
    {
        if (!dm.dmDisplayFixedOutput)
            __builtin_printf("\t%ld x %ld @ %ld Hz%s\n", dm.dmPelsWidth, dm.dmPelsHeight, dm.dmDisplayFrequency,
                             dm.dmDisplayFlags ? " (Interlaced)" : "");
        iModeNum++;
    }
}

int wmain(int argc, wchar_t *wargv[])
{
    UINT fArgument = 0;

    if (CompareStringOrdinal(L"/enumerate", -1, wargv[1], -1, TRUE) == CSTR_EQUAL && argc == 2)
        fArgument = 1;
    else if (CompareStringOrdinal(L"/get", -1, wargv[1], -1, TRUE) == CSTR_EQUAL && argc == 3)
        fArgument = 2;
    else if (CompareStringOrdinal(L"/set", -1, wargv[1], -1, TRUE) == CSTR_EQUAL && argc == 7)
        fArgument = 3;
    else if (CompareStringOrdinal(L"/save", -1, wargv[1], -1, TRUE) == CSTR_EQUAL && argc == 7)
        fArgument = 4;
    else
    {
        __builtin_printf("DisplayConfig:\n\n"
                         "\t/Enumerate\n\t\tEnumerate displays.\n\n"
                         "\t/Get <Index>\n\t\tObtain display modes for a given display.\n\n"
                         "\t/Set <Index> <Width> <Height> <Refresh Rate> <Orientation>\n\t\tSet the display mode with "
                         "specified parameters.\n\n"
                         "\t/Save <Index> <Width> <Height> <Refresh Rate> <Orientation>\n\t\tSaves the specified "
                         "display mode to the registry.\n\n");
        return 0;
    }

    UINT numPathArrayElements = 0, numModeInfoArrayElements = 0;
    GetDisplayConfigBufferSizes(QDC_ONLY_ACTIVE_PATHS, &numPathArrayElements, &numModeInfoArrayElements);

    HANDLE hHeap = GetProcessHeap();

    DISPLAYCONFIG_PATH_INFO *pathArray = HeapAlloc(hHeap, 0, sizeof(DISPLAYCONFIG_PATH_INFO) * numPathArrayElements);
    DISPLAYCONFIG_MODE_INFO *modeInfoArray =
        HeapAlloc(hHeap, 0, sizeof(DISPLAYCONFIG_MODE_INFO) * numModeInfoArrayElements);
    QueryDisplayConfig(QDC_ONLY_ACTIVE_PATHS, &numPathArrayElements, pathArray, &numModeInfoArrayElements,
                       modeInfoArray, NULL);

    switch (fArgument)
    {
    case 1: {
        for (UINT32 nIndex = 0; nIndex < numPathArrayElements; nIndex++)
        {
            __builtin_printf("%d : ", nIndex);
            DisplayConfigOutputDisplayName(&pathArray[nIndex]);
        }
    }
    break;

    case 2: {
        LONG nIndex = _wtol(wargv[2]);
        if (numPathArrayElements - 1 >= nIndex)
            DisplayConfigOutputDisplayModes(&pathArray[nIndex]);
        else
            __builtin_printf("Error: Invalid Display Index.");
    }
    break;

    case 3:
    case 4: {
        LONG nIndex = _wtol(wargv[2]);
        DEVMODEW dm = {.dmSize = sizeof(DEVMODEW),
                       .dmPelsWidth = _wtol(wargv[3]),
                       .dmPelsHeight = _wtol(wargv[4]),
                       .dmDisplayFrequency = _wtol(wargv[5]),
                       .dmFields = DM_PELSWIDTH | DM_PELSHEIGHT | DM_DISPLAYFREQUENCY | DM_DISPLAYORIENTATION};

        if (CompareStringOrdinal(L"landscape", -1, wargv[6], -1, TRUE) == CSTR_EQUAL)
            dm.dmDisplayOrientation = DMDO_DEFAULT;
        else if (CompareStringOrdinal(L"landscape-flipped", -1, wargv[6], -1, TRUE) == CSTR_EQUAL)
            dm.dmDisplayOrientation = DMDO_180;
        else if (CompareStringOrdinal(L"portrait", -1, wargv[6], -1, TRUE) == CSTR_EQUAL)
            dm.dmDisplayOrientation = DMDO_90;
        else if (CompareStringOrdinal(L"portrait-flipped", -1, wargv[6], -1, TRUE) == CSTR_EQUAL)
            dm.dmDisplayOrientation = DMDO_270;

        if (numPathArrayElements - 1 >= nIndex)
            if (DisplayConfigSetDisplayMode(&pathArray[nIndex], &dm, CDS_TEST))
                __builtin_printf("Error: Invalid Display Mode.");
            else
                DisplayConfigSetDisplayMode(&pathArray[nIndex], &dm, fArgument == 3 ? 0 : CDS_UPDATEREGISTRY);
        else
            __builtin_printf("Error: Invalid Display Index.");
    }
    break;
    }
    return 0;
}