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// This source code is released into the public domain.
module;
#include <expected>
#include <filesystem>
#include <optional>
#include <ranges>
#include <paths.h>
#include <unistd.h>
export module nihil.posix:find_in_path;
import nihil.error;
import :fd;
import :getenv;
namespace nihil {
// Find an executable by searching the given path string, which should be a colon-separated list of
// directories, and return the full path. If the file can't be found or is not executable, returns
// an appropriate error.
export [[nodiscard]] auto find_in_path(std::filesystem::path const &file, std::string_view path)
-> std::expected<std::filesystem::path, error>
{
auto try_return =
[](std::filesystem::path file) -> std::expected<std::filesystem::path, error> {
auto ret = ::access(file.string().c_str(), X_OK);
if (ret == 0)
return {std::move(file)};
return std::unexpected(error(std::errc(errno)));
};
// Absolute pathname skips the search.
if (file.is_absolute())
return try_return(file);
// Default to ENOENT as the error.
auto err = error(std::errc::no_such_file_or_directory);
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;
// If we get an error other than ENOENT, cache it to return to the caller.
// This means we can propagate access() errors.
else if (ret.error().root_cause() != std::errc::no_such_file_or_directory)
err = std::move(ret.error());
}
return std::unexpected(std::move(err));
}
// 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 is not executable, returns an appropriate error.
export [[nodiscard]] auto
find_in_path(std::filesystem::path const &file) -> std::expected<std::filesystem::path, error>
{
auto const path = getenv("PATH").value_or(_PATH_DEFPATH); // NOLINT
return find_in_path(file, path);
}
} // namespace nihil
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