36 files changed, 352 insertions, 39 deletions
diff --git a/.clang-format b/.clang-format
new file mode 100644
index 0000000..c2dc3e0
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,6 @@
+TabWidth: 8
+IndentWidth: 8
+PPIndentWidth: -1
+UseTab: AlignWithSpaces
+IndentPPDirectives: AfterHash
+ColumnLimit: 100
+\ No newline at end of file
diff --git a/.gitignore b/.gitignore
index ad0c823..a8dc4b2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
-/build
+/build*
 /dist
 *.sw?
+/.idea
diff --git a/nihil.cli/command_tree.cc b/nihil.cli/command_tree.cc
index 7cea8da..2d14669 100644
--- a/nihil.cli/command_tree.cc
+++ b/nihil.cli/command_tree.cc
@@ -5,6 +5,7 @@
 module;
 
 #include <iostream>
+#include <memory>
 #include <print>
 #include <ranges>
 #include <string>
diff --git a/nihil.core/CMakeLists.txt b/nihil.core/CMakeLists.txt
index 4564640..2a7b3e2 100644
--- a/nihil.core/CMakeLists.txt
+++ b/nihil.core/CMakeLists.txt
@@ -1,6 +1,7 @@
 # This source code is released into the public domain.
 
 add_library(nihil.core STATIC)
+target_include_directories(nihil.core PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 target_sources(nihil.core
 	PUBLIC FILE_SET modules TYPE CXX_MODULES FILES
 	nihil.core.ccm
diff --git a/nihil.core/nihil.hh b/nihil.core/nihil.hh
new file mode 100644
index 0000000..cd7e789
--- /dev/null
+++ b/nihil.core/nihil.hh
@@ -0,0 +1,26 @@
+/*
+* This source code is released into the public domain.
+ */
+
+#ifndef NIHIL_HH_INCLUDED
+#define NIHIL_HH_INCLUDED
+
+#if __has_include(<sys/param.h>)
+#	include <sys/param.h>
+#endif
+
+#if defined(__FreeBSD_version)
+
+/* fexecve() added in FreeBSD 8.0 */
+#if (__FreeBSD_version >= 800000)
+#	define NIHIL_HAVE_FEXECVE
+#endif
+
+/* getenv_r() added in FreeBSD 15.0 */
+#if (__FreeBSD_version >= 1500000)
+#	define NIHIL_HAVE_GETENV_R
+#endif
+
+#endif // defined(__FreeBSD_version)
+
+#endif // !NIHIL_HH_INCLUDED
diff --git a/nihil.posix/CMakeLists.txt b/nihil.posix/CMakeLists.txt
index 6f410ce..62f6aaf 100644
--- a/nihil.posix/CMakeLists.txt
+++ b/nihil.posix/CMakeLists.txt
@@ -2,36 +2,40 @@
 
 add_library(nihil.posix STATIC)
 target_link_libraries(nihil.posix PRIVATE
-	nihil.error nihil.flagset nihil.guard nihil.monad)
+	nihil.core nihil.error nihil.flagset nihil.guard nihil.monad)
 
 target_sources(nihil.posix
 	PUBLIC FILE_SET modules TYPE CXX_MODULES FILES
 	posix.ccm
 
-	posix.argv.ccm
-	posix.ensure_dir.ccm
-	posix.exec.ccm
-	posix.fd.ccm
-	posix.getenv.ccm
-	posix.open.ccm
-	posix.process.ccm
-	posix.read_file.ccm
-	posix.rename.ccm
-	posix.spawn.ccm
-	posix.tempfile.ccm
-	posix.write_file.ccm
+	argv.ccm
+	ensure_dir.ccm
+	exec.ccm
+	execv.ccm
+	executor.ccm
+	fd.ccm
+	find_in_path.ccm
+	getenv.ccm
+	open.ccm
+	process.ccm
+	read_file.ccm
+	rename.ccm
+	spawn.ccm
+	tempfile.ccm
+	write_file.ccm
 
 	PRIVATE
-	posix.argv.cc
-	posix.ensure_dir.cc
-	posix.exec.cc
-	posix.getenv.cc
-	posix.fd.cc
-	posix.find_in_path.cc
-	posix.open.cc
-	posix.process.cc
-	posix.rename.cc
-	posix.tempfile.cc
+	argv.cc
+	ensure_dir.cc
+	exec.cc
+	execv.cc
+	getenv.cc
+	fd.cc
+	find_in_path.cc
+	open.cc
+	process.cc
+	rename.cc
+	tempfile.cc
 )
 
 if(NIHIL_TESTS)
diff --git a/nihil.posix/posix.argv.cc b/nihil.posix/argv.cc
index e6b1389..e6b1389 100644
--- a/nihil.posix/posix.argv.cc
+++ b/nihil.posix/argv.cc
diff --git a/nihil.posix/posix.argv.ccm b/nihil.posix/argv.ccm
index 6f60f4b..6f60f4b 100644
--- a/nihil.posix/posix.argv.ccm
+++ b/nihil.posix/argv.ccm
diff --git a/nihil.posix/posix.ensure_dir.cc b/nihil.posix/ensure_dir.cc
index 88e8898..88e8898 100644
--- a/nihil.posix/posix.ensure_dir.cc
+++ b/nihil.posix/ensure_dir.cc
diff --git a/nihil.posix/posix.ensure_dir.ccm b/nihil.posix/ensure_dir.ccm
index fa92a90..fa92a90 100644
--- a/nihil.posix/posix.ensure_dir.ccm
+++ b/nihil.posix/ensure_dir.ccm
diff --git a/nihil.posix/posix.exec.cc b/nihil.posix/exec.cc
index 5bdcbf7..5bdcbf7 100644
--- a/nihil.posix/posix.exec.cc
+++ b/nihil.posix/exec.cc
diff --git a/nihil.posix/posix.exec.ccm b/nihil.posix/exec.ccm
index 6098318..6098318 100644
--- a/nihil.posix/posix.exec.ccm
+++ b/nihil.posix/exec.ccm
diff --git a/nihil.posix/executor.ccm b/nihil.posix/executor.ccm
new file mode 100644
index 0000000..f348dc8
--- /dev/null
+++ b/nihil.posix/executor.ccm
@@ -0,0 +1,27 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <concepts>
+#include <type_traits>
+
+export module nihil.posix:executor;
+
+namespace nihil {
+
+/*
+ * A concept to mark spawn executors.
+ */
+
+export struct exec_tag{};
+
+export template<typename T>
+concept executor =
+	requires (T e) {
+		std::same_as<exec_tag, typename std::remove_cvref_t<T>::tag>;
+		{ e.exec() };
+	};
+
+} // namespace nihil
diff --git a/nihil.posix/execv.cc b/nihil.posix/execv.cc
new file mode 100644
index 0000000..63f9698
--- /dev/null
+++ b/nihil.posix/execv.cc
@@ -0,0 +1,43 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <coroutine>
+#include <expected>
+#include <format>
+#include <string>
+#include <utility>
+
+#include <err.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+extern char **environ;
+
+module nihil.posix;
+
+import nihil.error;
+import nihil.monad;
+
+namespace nihil {
+
+execv::execv(std::filesystem::path path, argv &&args) noexcept
+	: m_path(std::move(path))
+	, m_args(std::move(args))
+{
+}
+
+auto execv::exec(this execv &self) -> std::expected<void, error>
+{
+	::execve(self.m_path.string().c_str(), self.m_args.data(), environ);
+	return std::unexpected(error("execve failed", error(std::errc(errno))));
+}
+
+execv::execv(execv &&) noexcept = default;
+execv::execv(execv const &) = default;
+auto execv::operator=(this execv &, execv &&) -> execv & = default;
+auto execv::operator=(this execv &, execv const &) -> execv & = default;
+
+} // namespace nihil
diff --git a/nihil.posix/execv.ccm b/nihil.posix/execv.ccm
new file mode 100644
index 0000000..ca036a1
--- /dev/null
+++ b/nihil.posix/execv.ccm
@@ -0,0 +1,47 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <expected>
+#include <filesystem>
+#include <string>
+
+export module nihil.posix:execv;
+
+import nihil.error;
+import :argv;
+import :executor;
+
+namespace nihil {
+
+/*
+ * execv: use a filename and an argument vector to call ::execve().
+ * This is the lowest-level executor which all others are implemented
+ * in terms of, if fexecve is not available.
+ *
+ * TODO: Should have a way to pass the environment (envp).
+ */
+export struct execv final
+{
+	using tag = exec_tag;
+
+	execv(std::filesystem::path, argv &&) noexcept;
+
+	[[nodiscard]] auto exec(this execv &) -> std::expected<void, error>;
+
+	// Movable
+	execv(execv &&) noexcept;
+	auto operator=(this execv &, execv &&) noexcept -> execv &;
+
+	// Copyable.
+	execv(execv const &);
+	auto operator=(this execv &, execv const &) -> execv &;
+
+private:
+	std::filesystem::path	m_path;
+	argv			m_args;
+};
+
+} // namespace nihil
diff --git a/nihil.posix/posix.fd.cc b/nihil.posix/fd.cc
index 6d5e54f..6d5e54f 100644
--- a/nihil.posix/posix.fd.cc
+++ b/nihil.posix/fd.cc
diff --git a/nihil.posix/posix.fd.ccm b/nihil.posix/fd.ccm
index b937f46..b937f46 100644
--- a/nihil.posix/posix.fd.ccm
+++ b/nihil.posix/fd.ccm
diff --git a/nihil.posix/fexecv.ccm b/nihil.posix/fexecv.ccm
new file mode 100644
index 0000000..5ad6c62
--- /dev/null
+++ b/nihil.posix/fexecv.ccm
@@ -0,0 +1,53 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <expected>
+#include <string>
+
+#include "nihil.hh"
+
+#ifdef NIHIL_HAVE_FEXECVE
+
+export module nihil.posix:fexecv;
+
+import nihil.error;
+import :argv;
+import :executor;
+import :fd;
+
+namespace nihil {
+
+/*
+ * fexecv: use a file descriptor and an argument vector to call ::fexecve().
+ * This is the lowest-level executor which all others are implemented
+ * in terms of (if it's available).
+ *
+ * TODO: Should have a way to pass the environment (envp).
+ */
+export struct fexecv final {
+	using tag = exec_tag;
+
+	fexecv(fd &&execfd, argv &&args) noexcept;
+
+	[[nodiscard]] auto exec(this fexecv &self)
+		-> std::expected<void, error>;
+
+	// Movable
+	fexecv(fexecv &&) noexcept;
+	auto operator=(this fexecv &, fexecv &&) noexcept -> fexecv&;
+
+	// Not copyable (because we hold the open fd object)
+	fexecv(fexecv const &) = delete;
+	auto operator=(this fexecv &, fexecv const &) -> fexecv& = delete;
+
+private:
+	fd	m_execfd;
+	argv	m_args;
+};
+
+} // namespace nihil
+
+#endif	// NIHIL_HAVE_FEXECVE
+\ No newline at end of file
diff --git a/nihil.posix/find_in_path.cc b/nihil.posix/find_in_path.cc
new file mode 100644
index 0000000..7b03faa
--- /dev/null
+++ b/nihil.posix/find_in_path.cc
@@ -0,0 +1,52 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <filesystem>
+#include <optional>
+#include <ranges>
+#include <string>
+
+#include <fcntl.h>
+#include <paths.h>
+#include <unistd.h>
+
+module nihil.posix;
+
+namespace nihil {
+
+auto find_in_path(std::filesystem::path const &file) -> std::optional<std::filesystem::path>
+{
+	using namespace std::literals;
+
+	auto try_return = [](std::filesystem::path file)
+		-> std::optional<std::filesystem::path>
+	{
+		auto ret = ::access(file.string().c_str(), X_OK);
+		if (ret == 0)
+			return {std::move(file)};
+		return {};
+	};
+
+	// Absolute pathname skips the search.
+	if (file.is_absolute())
+		return try_return(file);
+
+	auto path = getenv("PATH").value_or(_PATH_DEFPATH);
+
+	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_return(sdir / file); ret)
+			return ret;
+	}
+
+	return {};
+}
+
+} // namespace nihil
diff --git a/nihil.posix/find_in_path.ccm b/nihil.posix/find_in_path.ccm
new file mode 100644
index 0000000..4988a12
--- /dev/null
+++ b/nihil.posix/find_in_path.ccm
@@ -0,0 +1,24 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <filesystem>
+#include <optional>
+
+export module nihil.posix:find_in_path;
+
+import nihil.error;
+import :fd;
+
+namespace nihil {
+
+/*
+ * Find an executable in $PATH and return the full path.  If $PATH is not set, uses _PATH_DEFPATH.
+ * If the file can't be found or opened, returns std::nullopt.
+ */
+export [[nodiscard]] auto find_in_path(std::filesystem::path const &file)
+	-> std::optional<std::filesystem::path>;
+
+} // namespace nihil
diff --git a/nihil.posix/posix.getenv.cc b/nihil.posix/getenv.cc
index 36df950..ad93305 100644
--- a/nihil.posix/posix.getenv.cc
+++ b/nihil.posix/getenv.cc
@@ -1,4 +1,3 @@
-
 /*
  * This source code is released into the public domain.
  */
@@ -13,6 +12,8 @@ module;
 
 #include <unistd.h>
 
+#include "nihil.hh"
+
 module nihil.posix;
 
 import nihil.error;
@@ -21,10 +22,12 @@ namespace nihil {
 
 auto getenv(std::string_view varname) -> std::expected<std::string, error>
 {
+	auto cvarname = std::string(varname);
+
+#ifdef NIHIL_HAVE_GETENV_R
 	// Start with a buffer of this size, and double it every iteration.
 	constexpr auto bufinc = std::size_t{1024};
 
-	auto cvarname = std::string(varname);
 	auto buf = std::vector<char>(bufinc);
 	for (;;) {
 		auto const ret = ::getenv_r(cvarname.c_str(),
@@ -40,6 +43,12 @@ auto getenv(std::string_view varname) -> std::expected<std::string, error>
 
 		return std::unexpected(error(std::errc(errno)));
 	}
+#else // NIHIL_HAVE_GETENV_R
+	auto *v = ::getenv(cvarname.c_str());
+	if (v == nullptr)
+		return std::unexpected(error(std::errc(errno)));
+	return {std::string(v)};
+#endif // NIHIL_HAVE_GETENV_R
 }
 
 } // namespace nihil
diff --git a/nihil.posix/posix.getenv.ccm b/nihil.posix/getenv.ccm
index 465f7e7..465f7e7 100644
--- a/nihil.posix/posix.getenv.ccm
+++ b/nihil.posix/getenv.ccm
diff --git a/nihil.posix/posix.open.cc b/nihil.posix/open.cc
index 9ef6538..9ef6538 100644
--- a/nihil.posix/posix.open.cc
+++ b/nihil.posix/open.cc
diff --git a/nihil.posix/posix.open.ccm b/nihil.posix/open.ccm
index eaedacd..eaedacd 100644
--- a/nihil.posix/posix.open.ccm
+++ b/nihil.posix/open.ccm
diff --git a/nihil.posix/posix.find_in_path.cc b/nihil.posix/open_in_path.cc
index 6be963c..30021ca 100644
--- a/nihil.posix/posix.find_in_path.cc
+++ b/nihil.posix/open_in_path.cc
@@ -16,8 +16,7 @@ module nihil.posix;
 
 namespace nihil {
 
-auto find_in_path(std::filesystem::path const &file)
-	-> std::optional<fd>
+auto open_in_path(std::filesystem::path const &file) -> std::optional<fd>
 {
 	using namespace std::literals;
 
diff --git a/nihil.posix/open_in_path.ccm b/nihil.posix/open_in_path.ccm
new file mode 100644
index 0000000..1fae56b
--- /dev/null
+++ b/nihil.posix/open_in_path.ccm
@@ -0,0 +1,23 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <filesystem>
+#include <optional>
+
+export module nihil.posix:find_in_path;
+
+import nihil.error;
+import :fd;
+
+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>;
+
+} // namespace nihil
diff --git a/nihil.posix/posix.ccm b/nihil.posix/posix.ccm
index e63ad6b..ea13f81 100644
--- a/nihil.posix/posix.ccm
+++ b/nihil.posix/posix.ccm
@@ -9,6 +9,8 @@ module;
 #include <optional>
 #include <string>
 
+#include "nihil.hh"
+
 export module nihil.posix;
 
 import nihil.error;
@@ -16,7 +18,9 @@ import nihil.error;
 export import :argv;
 export import :ensure_dir;
 export import :exec;
+export import :execv;
 export import :fd;
+export import :find_in_path;
 export import :getenv;
 export import :open;
 export import :process;
@@ -26,14 +30,6 @@ export import :spawn;
 export import :tempfile;
 export import :write_file;
 
-export namespace nihil {
-
-/*
- * Find an executable in $PATH, open it with O_EXEC and return the fd.
- * If $PATH is not set, uses _PATH_DEFPATH.  If the file can't be found
- * or opened, returns std::nullopt.
- */
-[[nodiscard]] auto find_in_path(std::filesystem::path const &file)
-	-> std::optional<fd>;
-
-} // namespace nihil
+#ifdef NIHIL_HAVE_FEXECVE
+export import :fexecv;
+#endif
diff --git a/nihil.posix/posix.process.cc b/nihil.posix/process.cc
index 70e84b7..70e84b7 100644
--- a/nihil.posix/posix.process.cc
+++ b/nihil.posix/process.cc
diff --git a/nihil.posix/posix.process.ccm b/nihil.posix/process.ccm
index 425deac..425deac 100644
--- a/nihil.posix/posix.process.ccm
+++ b/nihil.posix/process.ccm
diff --git a/nihil.posix/posix.read_file.ccm b/nihil.posix/read_file.ccm
index c950f67..be9e102 100644
--- a/nihil.posix/posix.read_file.ccm
+++ b/nihil.posix/read_file.ccm
@@ -4,6 +4,7 @@
 
 module;
 
+#include <algorithm>
 #include <expected>
 #include <filesystem>
 #include <iterator>
diff --git a/nihil.posix/posix.rename.cc b/nihil.posix/rename.cc
index 9203d08..9203d08 100644
--- a/nihil.posix/posix.rename.cc
+++ b/nihil.posix/rename.cc
diff --git a/nihil.posix/posix.rename.ccm b/nihil.posix/rename.ccm
index 796ec5b..796ec5b 100644
--- a/nihil.posix/posix.rename.ccm
+++ b/nihil.posix/rename.ccm
diff --git a/nihil.posix/posix.spawn.ccm b/nihil.posix/spawn.ccm
index 4cce334..4cce334 100644
--- a/nihil.posix/posix.spawn.ccm
+++ b/nihil.posix/spawn.ccm
diff --git a/nihil.posix/posix.tempfile.cc b/nihil.posix/tempfile.cc
index b1d3dee..b1d3dee 100644
--- a/nihil.posix/posix.tempfile.cc
+++ b/nihil.posix/tempfile.cc
diff --git a/nihil.posix/posix.tempfile.ccm b/nihil.posix/tempfile.ccm
index 82f3be4..82f3be4 100644
--- a/nihil.posix/posix.tempfile.ccm
+++ b/nihil.posix/tempfile.ccm
diff --git a/nihil.posix/posix.write_file.ccm b/nihil.posix/write_file.ccm
index 867e0db..867e0db 100644
--- a/nihil.posix/posix.write_file.ccm
+++ b/nihil.posix/write_file.ccm