✨ Can now pass command-line args to the exe we spawn

include/Cool/spawn_process.hpp

@@ -2,10 +2,13 @@
 #include <filesystem>
 #include <optional>
 #include <string>
+#include <vector>
 
 namespace Cool {
 
 /// Returns a non-empty optional containing an error message if something went wrong
-auto spawn_process(std::filesystem::path const& executable_absolute_path) -> std::optional<std::string>;
+/// You can pass command line args (argc / argv) as a vector of strings
+/// NB: you don't need to add quotes if your args contain spaces (e.g. `spawn_process(my_exe, {"Hello", "i have many words"})` will send two args: Hello and "i have many words")
+auto spawn_process(std::filesystem::path const& executable_absolute_path, std::vector<std::string> const& args = {}) -> std::optional<std::string>;
 
 } // namespace Cool

src/spawn_process.cpp

@@ -29,14 +29,22 @@ std::string GetLastErrorAsString()
     return message;
 }
 
-auto spawn_process_impl(std::filesystem::path const& executable_absolute_path) -> std::optional<std::string>
+auto spawn_process_impl(std::filesystem::path const& executable_absolute_path, std::vector<std::string> const& args) -> std::optional<std::string>
 {
     STARTUPINFO si;
     ZeroMemory(&si, sizeof(si));
     si.cb = sizeof(si);
     PROCESS_INFORMATION pi;
     ZeroMemory(&pi, sizeof(pi));
-    if (!CreateProcess(executable_absolute_path.string().c_str(), nullptr, nullptr, nullptr, false, 0, nullptr, nullptr, &si, &pi))
+
+    // Combine the exe path and arguments into a single command line
+    std::string command_line = '\"' + executable_absolute_path.string() + '\"'; // we need to add quotes in case exe path contains spaces
+    for (auto const& arg : args)
+        command_line += " \"" + arg + '\"';
+    auto cmd = std::vector<char>(command_line.begin(), command_line.end()); // The API needs a char* so we can't use std::string::c_str()
+    cmd.push_back('\0');
+
+    if (!CreateProcess(nullptr, cmd.data(), nullptr, nullptr, false, 0, nullptr, nullptr, &si, &pi))
         return GetLastErrorAsString();
 
     CloseHandle(pi.hProcess);
@@ -52,15 +60,24 @@ auto spawn_process_impl(std::filesystem::path const& executable_absolute_path) -
 #include <cstring>
 
 namespace {
-auto spawn_process_impl(std::filesystem::path const& executable_absolute_path) -> std::optional<std::string>
+auto spawn_process_impl(std::filesystem::path const& executable_absolute_path, std::vector<std::string> const& args) -> std::optional<std::string>
 {
     pid_t pid = fork();
 
     if (pid < 0)
         return std::string{"Fork failed: "} + strerror(errno);
 
     if (pid == 0) // We are in the child process:
-        execl(executable_absolute_path.string().c_str(), executable_absolute_path.string().c_str(), nullptr);
+    {
+        auto const exe_path   = executable_absolute_path.string(); // Store the string so that the c_str() is kept alive
+        auto       args_array = std::vector<const char*>{};
+        args_array.push_back(exe_path.c_str());
+        for (auto const& arg : args)
+            args_array.push_back(arg.c_str());
+        args_array.push_back(nullptr);
+
+        execv(exe_path.c_str(), args_array.data());
+    }
 
     return std::nullopt;
 }
@@ -72,10 +89,10 @@ auto spawn_process_impl(std::filesystem::path const& executable_absolute_path) -
 
 namespace Cool {
 
-auto spawn_process(std::filesystem::path const& executable_absolute_path) -> std::optional<std::string>
+auto spawn_process(std::filesystem::path const& executable_absolute_path, std::vector<std::string> const& args) -> std::optional<std::string>
 {
     assert(std::filesystem::weakly_canonical(executable_absolute_path) == executable_absolute_path);
-    return spawn_process_impl(executable_absolute_path);
+    return spawn_process_impl(executable_absolute_path, args);
 }
 
 } // namespace Cool

tests/dummy_exe.cpp

@@ -3,8 +3,11 @@
 #include <iomanip>
 #include <iostream>
 
-int main()
+int main(int argc, char** argv)
 {
+    for (int i = 1; i < argc; ++i)
+        std::cout << "Command-line arg: '" << argv[i] << "'\n";
+
     int prev_sec{};
     int count{0};
     while (count < 5)

tests/tests.cpp

@@ -1,9 +1,38 @@
 #include <iostream>
+#include <thread>
 #include "Cool/spawn_process.hpp"
 
 int main()
 {
+    using namespace std::literals;
+
     std::cout << "Start spawning process\n";
     Cool::spawn_process(EXECUTABLE_PATH);
     std::cout << "Done spawning process\n";
+
+    std::this_thread::sleep_for(6s);
+
+    std::cout << "Start spawning process\n";
+    Cool::spawn_process(EXECUTABLE_PATH, {"Hello"});
+    std::cout << "Done spawning process\n";
+
+    std::this_thread::sleep_for(6s);
+
+    std::cout << "Start spawning process\n";
+    Cool::spawn_process(EXECUTABLE_PATH, {"Hello", "World"});
+    std::cout << "Done spawning process\n";
+
+    std::this_thread::sleep_for(6s);
+
+    std::cout << "Start spawning process\n";
+    Cool::spawn_process(EXECUTABLE_PATH, {"Hello", "World", "two words"});
+    std::cout << "Done spawning process\n";
+
+    std::this_thread::sleep_for(6s);
+
+    std::cout << "Start spawning process\n";
+    Cool::spawn_process(EXECUTABLE_PATH, {"Hello", "World", "\\\"two words\\\""});
+    std::cout << "Done spawning process\n";
+
+    std::this_thread::sleep_for(6s);
 }