diff --git a/LibConf b/LibConf
index f0593e3..fb5242b 100644
--- a/LibConf
+++ b/LibConf
@@ -4,6 +4,7 @@ Import('env')
 mijin_sources = Split("""
     source/mijin/async/coroutine.cpp
     source/mijin/debug/symbol_info.cpp
+    source/mijin/io/process.cpp
     source/mijin/io/stream.cpp
     source/mijin/util/os.cpp
     source/mijin/types/name.cpp
diff --git a/source/mijin/io/process.cpp b/source/mijin/io/process.cpp
new file mode 100644
index 0000000..1521856
--- /dev/null
+++ b/source/mijin/io/process.cpp
@@ -0,0 +1,175 @@
+
+#include "./process.hpp"
+
+#include <algorithm>
+#include <sstream>
+#include "../util/iterators.hpp"
+#include "../util/string.hpp"
+
+namespace mijin
+{
+ProcessStream::~ProcessStream()
+{
+    if (handle) {
+        close();
+    }
+}
+
+StreamError ProcessStream::open(const char* command, FileOpenMode mode_)
+{
+    mode = mode_;
+    
+    const char* modeStr; // NOLINT(cppcoreguidelines-init-variables)
+    switch (mode_)
+    {
+        case FileOpenMode::READ:
+            modeStr = "r";
+            break;
+        case FileOpenMode::WRITE:
+            modeStr = "w";
+            break;
+        case FileOpenMode::READ_WRITE:
+            modeStr = "rw";
+            break;
+        default:
+            assert(!"Unsupported mode for ProcessStream::open()");
+            return StreamError::NOT_SUPPORTED;
+    }
+    handle = popen(command, modeStr); // NOLINT(cppcoreguidelines-owning-memory)
+    if (!handle) {
+        return StreamError::IO_ERROR;
+    }
+
+    return StreamError::SUCCESS;
+}
+
+int ProcessStream::close()
+{
+    assert(handle);
+    const int result = pclose(handle);
+    handle = nullptr;
+    return result;
+}
+
+StreamError ProcessStream::readRaw(std::span<std::uint8_t> buffer, bool partial, std::size_t* outBytesRead)
+{
+    assert(handle);
+    assert(mode == FileOpenMode::READ || mode == FileOpenMode::READ_WRITE);
+
+    if (bufferedChar >= 0 && buffer.size() > 0)
+    {
+        buffer[0] = static_cast<std::uint8_t>(bufferedChar);
+    }
+
+    const std::size_t readBytes = std::fread(buffer.data(), 1, buffer.size(), handle);
+    if (std::ferror(handle)) {
+        return StreamError::IO_ERROR;
+    }
+    if (!partial && readBytes < buffer.size()) {
+        return StreamError::IO_ERROR;
+    }
+    if (outBytesRead != nullptr)
+    {
+        *outBytesRead = readBytes + (bufferedChar >= 0 ? 1 : 0);
+    }
+    bufferedChar = -1;
+    return StreamError::SUCCESS;
+}
+
+StreamError ProcessStream::writeRaw(std::span<const std::uint8_t> buffer)
+{
+    assert(handle);
+    assert(mode == FileOpenMode::WRITE || mode == FileOpenMode::READ_WRITE);
+
+    const std::size_t written = std::fwrite(buffer.data(), 1, buffer.size(), handle);
+    if (written != buffer.size() || std::ferror(handle)) {
+        return StreamError::IO_ERROR;
+    }
+
+    return StreamError::SUCCESS;
+}
+
+std::size_t ProcessStream::tell()
+{
+    assert(handle);
+
+    return std::ftell(handle); // TODO: does this work?
+}
+
+StreamError ProcessStream::seek(std::intptr_t pos, SeekMode seekMode)
+{
+    (void) pos;
+    (void) seekMode;
+    return StreamError::NOT_SUPPORTED;
+}
+
+void ProcessStream::flush()
+{
+    const int result = std::fflush(handle);
+    assert(result == 0);
+}
+
+bool ProcessStream::isAtEnd()
+{
+    assert(handle);
+
+    if (bufferedChar >= 0) {
+        return false;
+    }
+
+    bufferedChar = std::fgetc(handle);
+    if (std::feof(handle)) {
+        return true;
+    }
+    return false;
+}
+
+StreamFeatures ProcessStream::getFeatures()
+{
+    if (handle)
+    {
+        return {
+            .read = (mode == FileOpenMode::READ),
+            .write = (mode == FileOpenMode::WRITE || mode == FileOpenMode::READ_WRITE),
+            .tell = true,
+            .seek = false
+        };
+    }
+    return {};
+}
+
+std::string shellEscape(const std::string& arg) noexcept
+{
+    std::ostringstream oss;
+    const bool requiresQuotes = std::any_of(arg.begin(), arg.end(), [&](const char chr) { return std::isspace(chr); });
+    if (requiresQuotes) {
+        oss << '"';
+    }
+    for (const char chr : arg)
+    {
+        // TODO: oh Windows this will probably be different
+        switch (chr)
+        {
+            case '"':
+            case '\'':
+            case '\\':
+            case '$':
+                oss << '\\';
+                break;
+        }
+        oss << chr;
+    }
+    if (requiresQuotes) {
+        oss << '"';
+    }
+    return oss.str();
+}
+
+std::string makeShellCommand(const std::vector<std::string>& args) noexcept
+{
+    using namespace mijin::pipe;
+    return args
+        | Map(&shellEscape)
+        | Join(" ");
+}
+} // namespace mijin
diff --git a/source/mijin/io/process.hpp b/source/mijin/io/process.hpp
new file mode 100644
index 0000000..7d8ce52
--- /dev/null
+++ b/source/mijin/io/process.hpp
@@ -0,0 +1,47 @@
+#pragma once
+
+#if !defined(MIJIN_IO_PROCESS_HPP_INCLUDED)
+#define MIJIN_IO_PROCESS_HPP_INCLUDED 1
+
+#include <vector>
+#include "./stream.hpp"
+
+namespace mijin
+{
+class ProcessStream : public Stream
+{
+private:
+    std::FILE* handle = nullptr;
+    FileOpenMode mode;
+    int bufferedChar; // for isAtEnd
+public:
+    ~ProcessStream() override;
+
+    StreamError open(const char* command, FileOpenMode mode_);
+    inline StreamError open(const std::string& command, FileOpenMode mode_) {
+        return open(command.c_str(), mode_);
+    }
+    inline StreamError open(const std::vector<std::string>& args, FileOpenMode mode_);
+    int close();
+    [[nodiscard]] inline bool isOpen() const { return handle != nullptr; }
+
+    // Stream overrides
+    StreamError readRaw(std::span<std::uint8_t> buffer, bool partial = false, std::size_t* outBytesRead = nullptr) override;
+    StreamError writeRaw(std::span<const std::uint8_t> buffer) override;
+    std::size_t tell() override;
+    StreamError seek(std::intptr_t pos, SeekMode seekMode = SeekMode::ABSOLUTE) override;
+    void flush() override;
+    bool isAtEnd() override;
+    StreamFeatures getFeatures() override;
+};
+
+[[nodiscard]] std::string shellEscape(const std::string& arg) noexcept;
+[[nodiscard]] std::string makeShellCommand(const std::vector<std::string>& args) noexcept;
+
+StreamError ProcessStream::open(const std::vector<std::string>& args, FileOpenMode mode_)
+{
+    return open(makeShellCommand(args), mode_);
+}
+}
+
+#endif // MIJIN_IO_PROCESS_HPP_INCLUDED
diff --git a/source/mijin/io/stream.hpp b/source/mijin/io/stream.hpp
index f8364e8..294cefa 100644
--- a/source/mijin/io/stream.hpp
+++ b/source/mijin/io/stream.hpp
@@ -48,10 +48,11 @@ enum class FileOpenMode
     READ_WRITE
 };
 
-enum class StreamError
+enum class [[nodiscard]] StreamError
 {
     SUCCESS,
     IO_ERROR,
+    NOT_SUPPORTED,
     UNKNOWN_ERROR
 };
 
diff --git a/source/mijin/util/iterators.hpp b/source/mijin/util/iterators.hpp
index 3a33743..9525e13 100644
--- a/source/mijin/util/iterators.hpp
+++ b/source/mijin/util/iterators.hpp
@@ -4,6 +4,7 @@
 #define MIJIN_UTIL_ITERATORS_HPP_INCLUDED 1
 
 #include <cstddef>
+#include <functional>
 #include <span>
 #include <string_view>
 #include <tuple>
@@ -247,6 +248,94 @@ auto replace(
     };
 }
 
+template<typename TIterator, typename TFunctor>
+struct MappingIterator
+{
+    using orig_value_type = typename std::iterator_traits<TIterator>::value_type;
+    using difference_type = std::ptrdiff_t;
+    using value_type = std::invoke_result_t<TFunctor, orig_value_type>;
+    using iterator_category = std::bidirectional_iterator_tag; // TODO?
+
+    TIterator base;
+    TFunctor functor;
+
+    MappingIterator(TIterator base_, TFunctor functor_) noexcept : base(base_), functor(std::move(functor_)) {}
+    MappingIterator(const MappingIterator&) noexcept = default;
+    MappingIterator(MappingIterator&&) noexcept = default;
+
+    MappingIterator& operator=(const MappingIterator&) noexcept = default;
+    MappingIterator& operator=(MappingIterator&&) noexcept = default;
+
+    value_type operator*() const noexcept
+    {
+        return functor(*base);
+    }
+
+    MappingIterator& operator++() noexcept
+    {
+        ++base;
+        return *this;
+    }
+
+    MappingIterator operator++(int) noexcept
+    {
+        ReplacingIterator copy(*this);
+        ++(*this);
+        return copy;
+    }
+
+    MappingIterator& operator--() noexcept
+    {
+        --base;
+        return *this;
+    }
+
+    MappingIterator operator--(int) noexcept
+    {
+        EnumeratingIterator copy(*this);
+        --(*this);
+        return copy;
+    }
+
+    bool operator==(const MappingIterator& other) const noexcept
+    {
+        return functor == other.functor && base == other.base;
+    }
+
+    bool operator!=(const MappingIterator& other) const noexcept
+    {
+        return !(*this == other);
+    }
+};
+
+template<typename TIterable, typename TFunctor>
+struct MappingRange : RangeAdapter
+{
+    using value_type = typename std::iterator_traits<decltype(std::begin(std::declval<TIterable>()))>::value_type;
+
+    RangeRef<TIterable> base;
+    TFunctor functor;
+
+    auto begin() const noexcept
+    {
+        return MappingIterator(base.begin(), functor);
+    }
+
+    auto end() const noexcept
+    {
+        return MappingIterator(base.end(), functor);
+    }
+};
+
+template<typename TIterable, typename TFunctor>
+auto map(TIterable&& iterable, TFunctor&& functor)
+{
+    return MappingRange<TIterable, TFunctor>{
+        .base = {std::forward<TIterable>(iterable)},
+        .functor = std::forward<TFunctor>(functor)
+    };
+}
+
 template<typename TFirstIterator, typename TSecondIterator>
 struct ChainingIterator
 {
@@ -419,6 +508,22 @@ auto operator|(Chain2<TFirstIterable> chain2, TSecondIterable&& secondIterable)
 {
     return chain(chain2.range.range, std::forward<TSecondIterable>(secondIterable));
 }
+
+template<typename T>
+struct Map
+{
+    T functor;
+
+    explicit Map(T functor_) : functor(std::move(functor_)) {}
+};
+template<typename T>
+Map(T) -> Map<T>;
+
+template<typename TIterable, typename TFunctor>
+auto operator|(TIterable&& iterable, Map<TFunctor> mapper)
+{
+    return map(std::forward<TIterable>(iterable), std::move(mapper.functor));
+}
 }
 } // namespace mijin
 
diff --git a/source/mijin/util/string.hpp b/source/mijin/util/string.hpp
index ab3b763..54efcc0 100644
--- a/source/mijin/util/string.hpp
+++ b/source/mijin/util/string.hpp
@@ -47,6 +47,22 @@ std::string join(const TRange& elements, const char* const delimiter)
     return oss.str();
 }
 
+namespace pipe
+{
+struct Join
+{
+    const char* delimiter;
+
+    explicit Join(const char* delimiter_) noexcept : delimiter(delimiter_) {}
+};
+
+template<typename TIterable>
+auto operator|(TIterable&& iterable, const Join& joiner)
+{
+    return join(std::forward<TIterable>(iterable), joiner.delimiter);
+}
+}
+
 } // namespace mijin
 
 #endif // !defined(MIJIN_UTIL_STRING_HPP_INCLUDED)