无法从伪终端读取

我写了一个高级包装和命令集合，它使用RProc/RPMsg接口与微处理器进行通信，为了尽可能多地测试我为它编写了单元测试一个Linux伪终端代替'真实'的界面。无法从伪终端读取

我的测试没有奏效。我最终简化了测试，它没有包含我的代码痕迹点 - 它仍然不能正常工作：

BOOST_AUTO_TEST_CASE(constructor) 
{ 
    const auto master_pty = ::posix_openpt(O_RDWR); 
    BOOST_REQUIRE(master_pty != -1); 
    BOOST_REQUIRE(::grantpt(master_pty) != -1); 
    BOOST_REQUIRE(::unlockpt(master_pty) != -1); 

    const auto slave_pty_name = ::ptsname(master_pty); 
    const auto slave_pty = ::open(slave_pty_name, O_RDWR); 
    BOOST_REQUIRE(slave_pty != -1); 

    const auto in_data = std::array<std::uint8_t, 4>{1, 2, 3, 4}; 
    const auto bytes_written = ::write(master_pty, in_data.data(), in_data.size()); 
    if (bytes_written < 0) { 
     BOOST_FAIL("Failed to write: " << errno); 
    } 
    BOOST_REQUIRE_EQUAL(in_data.size(), bytes_written); 

    auto out_data = std::array<std::uint8_t, in_data.size()>{}; 
    const auto bytes_read = ::read(slave_pty, out_data.data(), out_data.size()); 
    BOOST_CHECK_EQUAL(bytes_read, bytes_written); 
    if (bytes_read < 0) { 
     BOOST_FAIL("::read failed: " << errno); 
    } 

    ::close(slave_pty); 
    ::close(master_pty); 
}

它的输出是：

*** 1 failure is detected in the test module "cmPTP Test Suite" 
# cmPTP-manager-test -l all --run_test=comms_rproc_interface/constructor 
Running 1 test case... 
Entering test module "cmPTP Test Suite" 
interface_test.cpp(17): Entering test suite "comms_rproc_interface" 
interface_test.cpp(19): Entering test case "constructor" 
interface_test.cpp(23): info: check master_pty != -1 has passed 
interface_test.cpp(24): info: check grantpt(master_pty) != -1 has passed 
interface_test.cpp(25): info: check unlockpt(master_pty) != -1 has passed 
interface_test.cpp(32): info: check slave_pty != -1 has passed 
interface_test.cpp(72): info: check in_data.size() == bytes_written has passed 
interface_test.cpp(77): error: in "comms_rproc_interface/constructor": check bytes_read == bytes_written has failed [0 != 4] 
interface_test.cpp(19): Leaving test case "constructor"; testing time: 15282us 
interface_test.cpp(17): Leaving test suite "comms_rproc_interface"; testing time: 15931us 
Leaving test module "cmPTP Test Suite"; testing time: 16879us 

*** 1 failure is detected in the test module "cmPTP Test Suite"

我可以写我的4字节好，但是从来没有任何东西存在。为什么？

来源

2017-05-06 cmannett85

这看起来并不像读出的实际上是失败了，但它并没有检索字节。写入缓冲区是否已被刷新？ – starturtle

@starturtle应该有：“POSIX要求在write（）返回后可以证明发生的读（2）返回新数据。注意并非所有的文件系统都符合POSIX标准。”我当然认为Linux/EXT4符合POSIX标准......我如何强制刷新？ – cmannett85

@starturtle其实它只是在我身上发现PTS是_two_文件描述符，所以上述不适用。 – cmannett85

这是因为我忘了我正在创建一个伪终端而不是一个串行设备。 PTY正在将我的输入值视为ASCII（可能会使它变得有点吓人），并且在刷新之前正在等待线返回 - 因此@starturtle关于刷新的评论是正确的，而不是以“正常”文件写入方式。

这繁琐SSCCE显示我应该怎么做它：

#include <unistd.h> 
#include <pty.h> 

#include <array> 
#include <iostream> 

int main() 
{ 
    // Make the PTY 'raw' to disable traditional terminal-like 
    // behaviour 
    struct termios ts; 
    cfmakeraw(&ts); 

    auto master_pty = -1; 
    auto slave_pty = -1; 
    if (::openpty(&master_pty, &slave_pty, nullptr, &ts, nullptr) < 0) { 
     std::cerr << "Cannot create PTY: " << errno << std::endl; 
     return EXIT_FAILURE; 
    } 

    const auto in_data = std::array<std::uint8_t, 5>{1, 2, 3, 4, 5}; 
    const auto bytes_written = ::write(master_pty, in_data.data(), in_data.size()); 
    if (bytes_written < 0) { 
     std::cerr << "Failed to write: " << errno << std::endl; 
     return EXIT_FAILURE; 
    } 

    auto out_data = std::array<std::uint8_t, in_data.size()>{}; 
    out_data.fill(0); 

    const auto bytes_read = ::read(slave_pty, out_data.data(), out_data.size()); 
    if (bytes_read < 0) { 
     std::cerr << "::read failed: " << errno << std::endl; 
     return EXIT_FAILURE; 
    } 

    for (auto&& c : out_data) { 
     std::cout << static_cast<int>(c); 
    } 
    std::cout << std::endl; 

    ::close(slave_pty); 
    ::close(master_pty); 
}

来源

2017-05-07 10:12:55 cmannett85

无法从伪终端读取

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