src/type3_AndroidCloud/anbox-master/external/process-cpp-minimal/README.md

   1 process-cpp         {#mainpage}
   2 ===========
   3
   4 process-cpp is a simple and straightforward wrapper around process creation and
   5 control targeted towards linux. It helps both with handling child processes and with
   6 interacting with the current process. Some of its features include:
   7
   8  - Thread-safe get/set/unset operation on the current process's environment.
   9  - Throwing and non-throwing overloads of functions when system calls are involved.
  10  - Seamless redirection of input, output and error streams of child processes.
  11  - Type-safe interaction with the virtual proc filesystem, both for reading & writing.
  12
  13 The library's main purpose is to assist in testing and when a software component
  14 needs to carry out process creation/control tasks, e.g., a graphical shell. To this end,
  15 the library is extensively tested and tries to ensure fail-safe operation as much as possible.
  16
  17 A simple echo
  18 -------------
  19
  20 ~~~~~~~~~~~~~{.cpp}
  21 // Fork and run a simple echo:
  22 posix::ChildProcess child = posix::fork(
  23             []()
  24             {
  25                 std::string line;
  26                 while(true)
  27                 {
  28                     std::cin >> line;
  29                     std::cout << line << std::endl;
  30                 }
  31                 return EXIT_FAILURE;
  32             },
  33             posix::StandardStreamFlags()
  34                 .set(posix::StandardStream::stdin)
  35                 .set(posix::StandardStream::stdout));
  36
  37 // Check that the resulting process has a valid pid.
  38 EXPECT_TRUE(child.pid() > 0);
  39
  40 // Check on echo functionality.
  41 const std::string echo_value{"42"};
  42 child.cin() << echo_value << std::endl;
  43 std::string line; child.cout() >> line;
  44 EXPECT_EQ(echo_value, line);
  45
  46 // Stop the process and synchronize with the process changing state.
  47 EXPECT_NO_THROW(child.send_signal(posix::Signal::sig_stop));
  48 auto result = child.wait_for(posix::wait::Flag::untraced);
  49 EXPECT_EQ(posix::wait::Result::Status::stopped,
  50           result.status);
  51 EXPECT_EQ(posix::Signal::sig_stop,
  52           result.detail.if_stopped.signal);
  53
  54 // Kill the stopped process and synchronize to its state change.
  55 EXPECT_NO_THROW(child.send_signal(posix::Signal::sig_kill));
  56 result = child.wait_for(posix::wait::Flag::untraced);
  57 EXPECT_EQ(posix::wait::Result::Status::signaled,
  58           result.status);
  59 EXPECT_EQ(posix::Signal::sig_kill,
  60           result.detail.if_signaled.signal);
  61 ~~~~~~~~~~~~~
  62
  63 Adjusting OOM Score Values
  64 --------------------------
  65
  66 ~~~~~~~~~~~~~{.cpp}
  67 // Setup the manipulator with a well-known value.
  68 posix::linux::proc::process::OomScoreAdj oom_score_adj
  69 {
  70     posix::linux::proc::process::OomScoreAdj::max_value()
  71 };
  72 // Apply the manipulator to the current process
  73 EXPECT_NO_THROW(posix::this_process::instance() << oom_score_adj);
  74 // Read back the manipulators value for the current process
  75 EXPECT_NO_THROW(posix::this_process::instance() >> oom_score_adj);
  76 // And check that applying the manipulator was successful.
  77 EXPECT_EQ(posix::linux::proc::process::OomScoreAdj::max_value(),
  78           oom_score_adj.value);
  79 // Instantiate the observer...
  80 posix::linux::proc::process::OomScore oom_score;
  81 // ... and fill in its value for the current process.
  82 EXPECT_NO_THROW(posix::this_process::instance() >> oom_score);
  83 // Check that applying the manipulator before results in adjustments to the
  84 // OOM score.
  85 EXPECT_TRUE(is_approximately_equal(oom_score.value, posix::linux::proc::process::OomScoreAdj::max_value()));
  86 ~~~~~~~~~~~~~