1 files changed, 37 insertions, 9 deletions
diff --git a/nihil.posix/open_in_path.ccm b/nihil.posix/open_in_path.ccm
index d4c090d..7ff5812 100644
--- a/nihil.posix/open_in_path.ccm
+++ b/nihil.posix/open_in_path.ccm
@@ -1,23 +1,51 @@
-/*
- * This source code is released into the public domain.
- */
-
+// This source code is released into the public domain.
 module;
 
 #include <filesystem>
 #include <optional>
+#include <ranges>
+#include <string>
+
+#include <paths.h>
 
 export module nihil.posix:open_in_path;
 
 import nihil.error;
 import :fd;
+import :getenv;
+import :open;
 
 namespace nihil {
 
-/*
- * Find an executable in $PATH and open it with O_EXEC.  If $PATH is not set, uses _PATH_DEFPATH.
- * If the file can't be found or opened, returns std::nullopt.
- */
-export [[nodiscard]] auto open_in_path(std::filesystem::path const &file) -> std::optional<fd>;
+// Find an executable in $PATH and open it with O_EXEC.  If $PATH is not set, uses _PATH_DEFPATH.
+// If the file can't be found or opened, returns std::nullopt.
+export [[nodiscard]] auto open_in_path(std::filesystem::path const &file) -> std::optional<fd>
+{
+	using namespace std::literals;
+
+	auto try_open = [](std::filesystem::path const &file) -> std::optional<fd> {
+		auto ret = open(file, open_exec);
+		if (ret)
+			return {std::move(*ret)};
+		return {};
+	};
+
+	// Absolute pathname skips the search.
+	if (file.is_absolute())
+		return try_open(file);
+
+	auto path = getenv("PATH").value_or(_PATH_DEFPATH); // NOLINT
+
+	for (auto &&dir : path | std::views::split(':')) {
+		// An empty $PATH element means cwd.
+		auto sdir = dir.empty() ? std::filesystem::path(".")
+		                        : std::filesystem::path(std::string_view(dir));
+
+		if (auto ret = try_open(sdir / file); ret)
+			return ret;
+	}
+
+	return {};
+}
 
 } // namespace nihil