From 121af20e80015aab41d5c31b000272bc8e73faf5 Mon Sep 17 00:00:00 2001
From: Hartmut Kaiser <hartmut.kaiser@gmail.com>
Date: Mon, 24 Jun 2024 13:27:18 -0500
Subject: [PATCH] Adding process example

---
 components/process/examples/CMakeLists.txt    | 28 +++++-
 .../process/examples/launch_command.cpp       | 86 +++++++++++++++++++
 2 files changed, 113 insertions(+), 1 deletion(-)
 create mode 100644 components/process/examples/launch_command.cpp

diff --git a/components/process/examples/CMakeLists.txt b/components/process/examples/CMakeLists.txt
index 6c6633577fb0..2089aa5249bc 100644
--- a/components/process/examples/CMakeLists.txt
+++ b/components/process/examples/CMakeLists.txt
@@ -1,4 +1,4 @@
-# Copyright (c) 2019 The STE||AR-Group
+# Copyright (c) 2024 The STE||AR-Group
 #
 # SPDX-License-Identifier: BSL-1.0
 # Distributed under the Boost Software License, Version 1.0. (See accompanying
@@ -13,4 +13,30 @@ if(HPX_WITH_EXAMPLES)
       tests.examples.components tests.examples.components.process
     )
   endif()
+else()
+  return()
 endif()
+
+set(example_programs launch_command)
+set(launch_command_FLAGS DEPENDENCIES process_component)
+
+foreach(example_program ${example_programs})
+  set(sources ${example_program}.cpp)
+
+  source_group("Source Files" FILES ${sources})
+
+  # add example executable
+  add_hpx_executable(
+    ${example_program} INTERNAL_FLAGS
+    SOURCES ${sources} ${${example_program}_FLAGS}
+    FOLDER "Examples/Components/Process"
+  )
+
+  add_hpx_example_target_dependencies("components.process" ${example_program})
+
+  if(HPX_WITH_TESTS AND HPX_WITH_TESTS_EXAMPLES)
+    add_hpx_example_test(
+      "components.process" ${example_program} ${${example_program}_PARAMETERS}
+    )
+  endif()
+endforeach()
diff --git a/components/process/examples/launch_command.cpp b/components/process/examples/launch_command.cpp
new file mode 100644
index 000000000000..0f83f6237625
--- /dev/null
+++ b/components/process/examples/launch_command.cpp
@@ -0,0 +1,86 @@
+//  Copyright (c) 2024 Hartmut Kaiser
+//
+//  SPDX-License-Identifier: BSL-1.0
+//  Distributed under the Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// This example demonstrates how the Process component can be used to launch
+// arbitrary commands on any of the participating localities.
+
+#include <hpx/hpx_main.hpp>
+#include <hpx/include/components.hpp>
+#include <hpx/include/process.hpp>
+#include <hpx/include/runtime.hpp>
+
+#include <iostream>
+#include <vector>
+
+inline int get_arraylen(char** arr)
+{
+    int count = 0;
+    if (nullptr != arr)
+    {
+        while (nullptr != arr[count])
+            ++count;    // simply count the strings
+    }
+    return count;
+}
+
+std::vector<std::string> get_environment()
+{
+    std::vector<std::string> env;
+#if defined(HPX_WINDOWS)
+    int len = get_arraylen(_environ);
+    std::copy(&_environ[0], &_environ[len], std::back_inserter(env));
+#elif defined(linux) || defined(__linux) || defined(__linux__) ||              \
+    defined(__AIX__) || defined(__APPLE__) || defined(__FreeBSD__)
+    int len = get_arraylen(environ);
+    std::copy(&environ[0], &environ[len], std::back_inserter(env));
+#else
+#error "Don't know, how to access the execution environment on this platform"
+#endif
+    return env;
+}
+
+int main()
+{
+    namespace process = hpx::components::process;
+
+    // use hpx::find_all_localities(); if you want to include the current
+    // locality as well
+    std::vector<hpx::id_type> localities = hpx::find_remote_localities();
+    std::vector<process::child> children;
+    children.reserve(localities.size());
+
+    for (auto const& locality : localities)
+    {
+        std::string exe = "ls";
+
+        // set up command line for launched executable
+        std::vector<std::string> args;
+        args.push_back(exe);
+        // args.push_back("...");    // add more arguments as needed
+
+        // set up environment for launched executable (propagate current env)
+        std::vector<std::string> env = get_environment();
+
+        // launch test executable
+        process::child c = process::execute(locality, process::run_exe(exe),
+            process::set_args(args), process::set_env(env),
+            process::start_in_dir("."), process::throw_on_error());
+
+        children.push_back(c);
+    }
+
+    // wait for the processes to start executing
+    hpx::wait_all(children);
+
+    // wait for the processes to terminate
+    for (auto& c : children)
+    {
+        int retval = c.wait_for_exit(hpx::launch::sync);
+        std::cout << retval << '\n';
+    }
+
+    return 0;
+}