diff --git a/init/Android.bp b/init/Android.bp
index db64f71..b1f0279 100644
--- a/init/Android.bp
+++ b/init/Android.bp
@@ -159,6 +159,7 @@
         "devices_test.cpp",
         "init_test.cpp",
         "property_service_test.cpp",
+        "result_test.cpp",
         "service_test.cpp",
         "ueventd_test.cpp",
         "util_test.cpp",
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 944fcee..28f60e6 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -151,9 +151,8 @@
 }
 
 static int do_domainname(const std::vector<std::string>& args) {
-    std::string err;
-    if (!WriteFile("/proc/sys/kernel/domainname", args[1], &err)) {
-        LOG(ERROR) << err;
+    if (auto result = WriteFile("/proc/sys/kernel/domainname", args[1]); !result) {
+        LOG(ERROR) << "Unable to write to /proc/sys/kernel/domainname: " << result.error();
         return -1;
     }
     return 0;
@@ -199,9 +198,8 @@
 }
 
 static int do_hostname(const std::vector<std::string>& args) {
-    std::string err;
-    if (!WriteFile("/proc/sys/kernel/hostname", args[1], &err)) {
-        LOG(ERROR) << err;
+    if (auto result = WriteFile("/proc/sys/kernel/hostname", args[1]); !result) {
+        LOG(ERROR) << "Unable to write to /proc/sys/kernel/hostname: " << result.error();
         return -1;
     }
     return 0;
@@ -244,22 +242,22 @@
     }
 
     if (args.size() >= 4) {
-        uid_t uid;
-        std::string decode_uid_err;
-        if (!DecodeUid(args[3], &uid, &decode_uid_err)) {
-            LOG(ERROR) << "Unable to find UID for '" << args[3] << "': " << decode_uid_err;
+        auto uid = DecodeUid(args[3]);
+        if (!uid) {
+            LOG(ERROR) << "Unable to decode UID for '" << args[3] << "': " << uid.error();
             return -1;
         }
-        gid_t gid = -1;
+        Result<gid_t> gid = -1;
 
         if (args.size() == 5) {
-            if (!DecodeUid(args[4], &gid, &decode_uid_err)) {
-                LOG(ERROR) << "Unable to find GID for '" << args[3] << "': " << decode_uid_err;
+            gid = DecodeUid(args[4]);
+            if (!gid) {
+                LOG(ERROR) << "Unable to decode GID for '" << args[3] << "': " << gid.error();
                 return -1;
             }
         }
 
-        if (lchown(args[1].c_str(), uid, gid) == -1) {
+        if (lchown(args[1].c_str(), *uid, *gid) == -1) {
             return -errno;
         }
 
@@ -651,9 +649,8 @@
 }
 
 static int do_write(const std::vector<std::string>& args) {
-    std::string err;
-    if (!WriteFile(args[1], args[2], &err)) {
-        LOG(ERROR) << err;
+    if (auto result = WriteFile(args[1], args[2]); !result) {
+        LOG(ERROR) << "Unable to write to file '" << args[1] << "': " << result.error();
         return -1;
     }
     return 0;
@@ -720,39 +717,38 @@
 }
 
 static int do_copy(const std::vector<std::string>& args) {
-    std::string data;
-    std::string err;
-    if (!ReadFile(args[1], &data, &err)) {
-        LOG(ERROR) << err;
+    auto file_contents = ReadFile(args[1]);
+    if (!file_contents) {
+        LOG(ERROR) << "Could not read input file '" << args[1] << "': " << file_contents.error();
         return -1;
     }
-    if (!WriteFile(args[2], data, &err)) {
-        LOG(ERROR) << err;
+    if (auto result = WriteFile(args[2], *file_contents); !result) {
+        LOG(ERROR) << "Could not write to output file '" << args[2] << "': " << result.error();
         return -1;
     }
     return 0;
 }
 
 static int do_chown(const std::vector<std::string>& args) {
-    uid_t uid;
-    std::string decode_uid_err;
-    if (!DecodeUid(args[1], &uid, &decode_uid_err)) {
-        LOG(ERROR) << "Unable to find UID for '" << args[1] << "': " << decode_uid_err;
+    auto uid = DecodeUid(args[1]);
+    if (!uid) {
+        LOG(ERROR) << "Unable to decode UID for '" << args[1] << "': " << uid.error();
         return -1;
     }
 
     // GID is optional and pushes the index of path out by one if specified.
     const std::string& path = (args.size() == 4) ? args[3] : args[2];
-    gid_t gid = -1;
+    Result<gid_t> gid = -1;
 
     if (args.size() == 4) {
-        if (!DecodeUid(args[2], &gid, &decode_uid_err)) {
-            LOG(ERROR) << "Unable to find GID for '" << args[2] << "': " << decode_uid_err;
+        gid = DecodeUid(args[2]);
+        if (!gid) {
+            LOG(ERROR) << "Unable to decode GID for '" << args[2] << "': " << gid.error();
             return -1;
         }
     }
 
-    if (lchown(path.c_str(), uid, gid) == -1) return -errno;
+    if (lchown(path.c_str(), *uid, *gid) == -1) return -errno;
 
     return 0;
 }
diff --git a/init/init_test.cpp b/init/init_test.cpp
index 2062290..58e3d75 100644
--- a/init/init_test.cpp
+++ b/init/init_test.cpp
@@ -156,10 +156,9 @@
                                "execute 3";
     // clang-format on
     // WriteFile() ensures the right mode is set
-    std::string err;
-    ASSERT_TRUE(WriteFile(std::string(dir.path) + "/a.rc", dir_a_script, &err));
+    ASSERT_TRUE(WriteFile(std::string(dir.path) + "/a.rc", dir_a_script));
 
-    ASSERT_TRUE(WriteFile(std::string(dir.path) + "/b.rc", "on boot\nexecute 5", &err));
+    ASSERT_TRUE(WriteFile(std::string(dir.path) + "/b.rc", "on boot\nexecute 5"));
 
     // clang-format off
     std::string start_script = "import " + std::string(first_import.path) + "\n"
diff --git a/init/parser.cpp b/init/parser.cpp
index c6f4f45..4c34c26 100644
--- a/init/parser.cpp
+++ b/init/parser.cpp
@@ -102,15 +102,14 @@
 bool Parser::ParseConfigFile(const std::string& path) {
     LOG(INFO) << "Parsing file " << path << "...";
     android::base::Timer t;
-    std::string data;
-    std::string err;
-    if (!ReadFile(path, &data, &err)) {
-        LOG(ERROR) << err;
+    auto config_contents = ReadFile(path);
+    if (!config_contents) {
+        LOG(ERROR) << "Unable to read config file '" << path << "': " << config_contents.error();
         return false;
     }
 
-    data.push_back('\n');  // TODO: fix parse_config.
-    ParseData(path, data);
+    config_contents->push_back('\n');  // TODO: fix parse_config.
+    ParseData(path, *config_contents);
     for (const auto& [section_name, section_parser] : section_parsers_) {
         section_parser->EndFile();
     }
diff --git a/init/property_service.cpp b/init/property_service.cpp
index 1db8cb7..e07550a 100644
--- a/init/property_service.cpp
+++ b/init/property_service.cpp
@@ -588,14 +588,14 @@
 // "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
 static void load_properties_from_file(const char* filename, const char* filter) {
     Timer t;
-    std::string data;
-    std::string err;
-    if (!ReadFile(filename, &data, &err)) {
-        PLOG(WARNING) << "Couldn't load property file: " << err;
+    auto file_contents = ReadFile(filename);
+    if (!file_contents) {
+        PLOG(WARNING) << "Couldn't load property file '" << filename
+                      << "': " << file_contents.error();
         return;
     }
-    data.push_back('\n');
-    load_properties(&data[0], filter);
+    file_contents->push_back('\n');
+    load_properties(file_contents->data(), filter);
     LOG(VERBOSE) << "(Loading properties from " << filename << " took " << t << ".)";
 }
 
diff --git a/init/result.h b/init/result.h
new file mode 100644
index 0000000..64fa69f
--- /dev/null
+++ b/init/result.h
@@ -0,0 +1,142 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// This file contains classes for returning a successful result along with an optional
+// arbitrarily typed return value or for returning a failure result along with an optional string
+// indicating why the function failed.
+
+// There are 3 classes that implement this functionality and one additional helper type.
+//
+// Result<T> either contains a member of type T that can be accessed using similar semantics as
+// std::optional<T> or it contains a std::string describing an error, which can be accessed via
+// Result<T>::error().
+//
+// Success is a typedef that aids in creating Result<T> that do not contain a return value.
+// Result<Success> is the correct return type for a function that either returns successfully or
+// returns an error value.  Returning Success() from a function that returns Result<Success> is the
+// correct way to indicate that a function without a return type has completed successfully.
+//
+// A successful Result<T> is constructed implicitly from any type that can be implicitly converted
+// to T or from the constructor arguments for T.  This allows you to return a type T directly from
+// a function that returns Result<T>.
+//
+// Error and ErrnoError are used to construct a Result<T> that has failed.  Each of these classes
+// take an ostream as an input and are implicitly cast to a Result<T> containing that failure.
+// ErrnoError() additionally appends ": " + strerror(errno) to the end of the failure string to aid
+// in interacting with C APIs.
+
+// An example of how to use these is below:
+// Result<U> CalculateResult(const T& input) {
+//   U output;
+//   if (!SomeOtherCppFunction(input, &output)) {
+//     return Error() << "SomeOtherCppFunction(" << input << ") failed";
+//   }
+//   if (!c_api_function(output)) {
+//     return ErrnoError() << "c_api_function(" << output << ") failed";
+//   }
+//   return output;
+// }
+//
+// auto output = CalculateResult(input);
+// if (!output) return Error() << "CalculateResult failed: " << output.error();
+// UseOutput(*output);
+
+#ifndef _INIT_RESULT_H
+#define _INIT_RESULT_H
+
+#include <errno.h>
+
+#include <sstream>
+#include <string>
+#include <variant>
+
+namespace android {
+namespace init {
+
+class Error {
+  public:
+    Error() : append_errno_(0) {}
+
+    template <typename T>
+    Error&& operator<<(T&& t) {
+        ss_ << std::forward<T>(t);
+        return std::move(*this);
+    }
+
+    const std::string str() const {
+        if (append_errno_) {
+            return ss_.str() + ": " + strerror(append_errno_);
+        }
+        return ss_.str();
+    }
+
+    Error(const Error&) = delete;
+    Error(Error&&) = delete;
+    Error& operator=(const Error&) = delete;
+    Error& operator=(Error&&) = delete;
+
+  protected:
+    Error(int append_errno) : append_errno_(append_errno) {}
+
+  private:
+    std::stringstream ss_;
+    int append_errno_;
+};
+
+class ErrnoError : public Error {
+  public:
+    ErrnoError() : Error(errno) {}
+};
+
+template <typename T>
+class Result {
+  public:
+    template <typename... U>
+    Result(U&&... result) : contents_(std::in_place_index_t<0>(), std::forward<U>(result)...) {}
+
+    Result(Error&& fb) : contents_(std::in_place_index_t<1>(), fb.str()) {}
+
+    bool has_value() const { return contents_.index() == 0; }
+
+    T& value() & { return std::get<0>(contents_); }
+    const T& value() const & { return std::get<0>(contents_); }
+    T&& value() && { return std::get<0>(std::move(contents_)); }
+    const T&& value() const && { return std::get<0>(std::move(contents_)); }
+
+    const std::string& error() const & { return std::get<1>(contents_); }
+    std::string&& error() && { return std::get<1>(std::move(contents_)); }
+    const std::string&& error() const && { return std::get<1>(std::move(contents_)); }
+
+    explicit operator bool() const { return has_value(); }
+
+    T& operator*() & { return value(); }
+    const T& operator*() const & { return value(); }
+    T&& operator*() && { return std::move(value()); }
+    const T&& operator*() const && { return std::move(value()); }
+
+    T* operator->() { return &value(); }
+    const T* operator->() const { return &value(); }
+
+  private:
+    std::variant<T, std::string> contents_;
+};
+
+using Success = std::monostate;
+
+}  // namespace init
+}  // namespace android
+
+#endif
diff --git a/init/result_test.cpp b/init/result_test.cpp
new file mode 100644
index 0000000..ca65013
--- /dev/null
+++ b/init/result_test.cpp
@@ -0,0 +1,222 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "result.h"
+
+#include "errno.h"
+
+#include <string>
+
+#include <gtest/gtest.h>
+
+using namespace std::string_literals;
+
+namespace android {
+namespace init {
+
+TEST(result, result_accessors) {
+    Result<std::string> result = "success";
+    ASSERT_TRUE(result);
+    ASSERT_TRUE(result.has_value());
+
+    EXPECT_EQ("success", *result);
+    EXPECT_EQ("success", result.value());
+
+    EXPECT_EQ('s', result->data()[0]);
+}
+
+TEST(result, result_accessors_rvalue) {
+    ASSERT_TRUE(Result<std::string>("success"));
+    ASSERT_TRUE(Result<std::string>("success").has_value());
+
+    EXPECT_EQ("success", *Result<std::string>("success"));
+    EXPECT_EQ("success", Result<std::string>("success").value());
+
+    EXPECT_EQ('s', Result<std::string>("success")->data()[0]);
+}
+
+TEST(result, result_success) {
+    Result<Success> result = Success();
+    ASSERT_TRUE(result);
+    ASSERT_TRUE(result.has_value());
+
+    EXPECT_EQ(Success(), *result);
+    EXPECT_EQ(Success(), result.value());
+}
+
+TEST(result, result_success_rvalue) {
+    // Success() doesn't actually create a Result<Success> object, but rather an object that can be
+    // implicitly constructed into a Result<Success> object.
+
+    auto MakeRvalueSuccessResult = []() -> Result<Success> { return Success(); };
+    ASSERT_TRUE(MakeRvalueSuccessResult());
+    ASSERT_TRUE(MakeRvalueSuccessResult().has_value());
+
+    EXPECT_EQ(Success(), *MakeRvalueSuccessResult());
+    EXPECT_EQ(Success(), MakeRvalueSuccessResult().value());
+}
+
+TEST(result, result_error) {
+    Result<Success> result = Error() << "failure" << 1;
+    ASSERT_FALSE(result);
+    ASSERT_FALSE(result.has_value());
+
+    EXPECT_EQ("failure1", result.error());
+}
+
+TEST(result, result_error_empty) {
+    Result<Success> result = Error();
+    ASSERT_FALSE(result);
+    ASSERT_FALSE(result.has_value());
+
+    EXPECT_EQ("", result.error());
+}
+
+TEST(result, result_error_rvalue) {
+    // Error() and ErrnoError() aren't actually used to create a Result<T> object.
+    // Under the hood, they are an intermediate class that can be implicitly constructed into a
+    // Result<T>.  This is needed both to create the ostream and because Error() itself, by
+    // definition will not know what the type, T, of the underlying Result<T> object that it would
+    // create is.
+
+    auto MakeRvalueErrorResult = []() -> Result<Success> { return Error() << "failure" << 1; };
+    ASSERT_FALSE(MakeRvalueErrorResult());
+    ASSERT_FALSE(MakeRvalueErrorResult().has_value());
+
+    EXPECT_EQ("failure1", MakeRvalueErrorResult().error());
+}
+
+TEST(result, result_errno_error) {
+    constexpr int test_errno = 6;
+    errno = test_errno;
+    Result<Success> result = ErrnoError() << "failure" << 1;
+
+    ASSERT_FALSE(result);
+    ASSERT_FALSE(result.has_value());
+
+    EXPECT_EQ("failure1: "s + strerror(test_errno), result.error());
+}
+
+TEST(result, constructor_forwarding) {
+    auto result = Result<std::string>(5, 'a');
+
+    ASSERT_TRUE(result);
+    ASSERT_TRUE(result.has_value());
+
+    EXPECT_EQ("aaaaa", *result);
+}
+
+struct ConstructorTracker {
+    static size_t constructor_called;
+    static size_t copy_constructor_called;
+    static size_t move_constructor_called;
+    static size_t copy_assignment_called;
+    static size_t move_assignment_called;
+
+    template <typename T>
+    ConstructorTracker(T&& string) : string(string) {
+        ++constructor_called;
+    }
+
+    ConstructorTracker(const ConstructorTracker& ct) {
+        ++copy_constructor_called;
+        string = ct.string;
+    }
+    ConstructorTracker(ConstructorTracker&& ct) noexcept {
+        ++move_constructor_called;
+        string = std::move(ct.string);
+    }
+    ConstructorTracker& operator=(const ConstructorTracker& ct) {
+        ++copy_assignment_called;
+        string = ct.string;
+        return *this;
+    }
+    ConstructorTracker& operator=(ConstructorTracker&& ct) noexcept {
+        ++move_assignment_called;
+        string = std::move(ct.string);
+        return *this;
+    }
+
+    std::string string;
+};
+
+size_t ConstructorTracker::constructor_called = 0;
+size_t ConstructorTracker::copy_constructor_called = 0;
+size_t ConstructorTracker::move_constructor_called = 0;
+size_t ConstructorTracker::copy_assignment_called = 0;
+size_t ConstructorTracker::move_assignment_called = 0;
+
+Result<ConstructorTracker> ReturnConstructorTracker(const std::string& in) {
+    if (in.empty()) {
+        return "literal string";
+    }
+    if (in == "test2") {
+        return ConstructorTracker(in + in + "2");
+    }
+    ConstructorTracker result(in + " " + in);
+    return result;
+};
+
+TEST(result, no_copy_on_return) {
+    // If returning parameters that may be used to implicitly construct the type T of Result<T>,
+    // then those parameters are forwarded to the construction of Result<T>.
+
+    // If returning an prvalue or xvalue, it will be move constructed during the construction of
+    // Result<T>.
+
+    // This check ensures that that is the case, and particularly that no copy constructors
+    // are called.
+
+    auto result1 = ReturnConstructorTracker("");
+    ASSERT_TRUE(result1);
+    EXPECT_EQ("literal string", result1->string);
+    EXPECT_EQ(1U, ConstructorTracker::constructor_called);
+    EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+    EXPECT_EQ(0U, ConstructorTracker::move_constructor_called);
+    EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+    EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+    auto result2 = ReturnConstructorTracker("test2");
+    ASSERT_TRUE(result2);
+    EXPECT_EQ("test2test22", result2->string);
+    EXPECT_EQ(2U, ConstructorTracker::constructor_called);
+    EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+    EXPECT_EQ(1U, ConstructorTracker::move_constructor_called);
+    EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+    EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+
+    auto result3 = ReturnConstructorTracker("test3");
+    ASSERT_TRUE(result3);
+    EXPECT_EQ("test3 test3", result3->string);
+    EXPECT_EQ(3U, ConstructorTracker::constructor_called);
+    EXPECT_EQ(0U, ConstructorTracker::copy_constructor_called);
+    EXPECT_EQ(2U, ConstructorTracker::move_constructor_called);
+    EXPECT_EQ(0U, ConstructorTracker::copy_assignment_called);
+    EXPECT_EQ(0U, ConstructorTracker::move_assignment_called);
+}
+
+TEST(result, die_on_access_failed_result) {
+    Result<std::string> result = Error();
+    ASSERT_DEATH(*result, "");
+}
+
+TEST(result, die_on_get_error_succesful_result) {
+    Result<std::string> result = "success";
+    ASSERT_DEATH(result.error(), "");
+}
+
+}  // namespace init
+}  // namespace android
diff --git a/init/selinux.cpp b/init/selinux.cpp
index 3a4a715..b9305ed 100644
--- a/init/selinux.cpp
+++ b/init/selinux.cpp
@@ -339,9 +339,8 @@
         }
     }
 
-    std::string err;
-    if (!WriteFile("/sys/fs/selinux/checkreqprot", "0", &err)) {
-        LOG(ERROR) << err;
+    if (auto result = WriteFile("/sys/fs/selinux/checkreqprot", "0"); !result) {
+        LOG(ERROR) << "Unable to write to /sys/fs/selinux/checkreqprot: " << result.error();
         panic();
     }
 
diff --git a/init/service.cpp b/init/service.cpp
index 6f756fa..e37888b 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -386,18 +386,20 @@
 }
 
 bool Service::ParseGroup(const std::vector<std::string>& args, std::string* err) {
-    std::string decode_uid_err;
-    if (!DecodeUid(args[1], &gid_, &decode_uid_err)) {
-        *err = "Unable to find GID for '" + args[1] + "': " + decode_uid_err;
+    auto gid = DecodeUid(args[1]);
+    if (!gid) {
+        *err = "Unable to decode GID for '" + args[1] + "': " + gid.error();
         return false;
     }
+    gid_ = *gid;
+
     for (std::size_t n = 2; n < args.size(); n++) {
-        gid_t gid;
-        if (!DecodeUid(args[n], &gid, &decode_uid_err)) {
-            *err = "Unable to find GID for '" + args[n] + "': " + decode_uid_err;
+        gid = DecodeUid(args[n]);
+        if (!gid) {
+            *err = "Unable to decode GID for '" + args[n] + "': " + gid.error();
             return false;
         }
-        supp_gids_.emplace_back(gid);
+        supp_gids_.emplace_back(*gid);
     }
     return true;
 }
@@ -527,26 +529,27 @@
 template <typename T>
 bool Service::AddDescriptor(const std::vector<std::string>& args, std::string* err) {
     int perm = args.size() > 3 ? std::strtoul(args[3].c_str(), 0, 8) : -1;
-    uid_t uid = 0;
-    gid_t gid = 0;
+    Result<uid_t> uid = 0;
+    Result<gid_t> gid = 0;
     std::string context = args.size() > 6 ? args[6] : "";
 
-    std::string decode_uid_err;
     if (args.size() > 4) {
-        if (!DecodeUid(args[4], &uid, &decode_uid_err)) {
-            *err = "Unable to find UID for '" + args[4] + "': " + decode_uid_err;
+        uid = DecodeUid(args[4]);
+        if (!uid) {
+            *err = "Unable to find UID for '" + args[4] + "': " + uid.error();
             return false;
         }
     }
 
     if (args.size() > 5) {
-        if (!DecodeUid(args[5], &gid, &decode_uid_err)) {
-            *err = "Unable to find GID for '" + args[5] + "': " + decode_uid_err;
+        gid = DecodeUid(args[5]);
+        if (!gid) {
+            *err = "Unable to find GID for '" + args[5] + "': " + gid.error();
             return false;
         }
     }
 
-    auto descriptor = std::make_unique<T>(args[1], args[2], uid, gid, perm, context);
+    auto descriptor = std::make_unique<T>(args[1], args[2], *uid, *gid, perm, context);
 
     auto old =
         std::find_if(descriptors_.begin(), descriptors_.end(),
@@ -585,11 +588,12 @@
 }
 
 bool Service::ParseUser(const std::vector<std::string>& args, std::string* err) {
-    std::string decode_uid_err;
-    if (!DecodeUid(args[1], &uid_, &decode_uid_err)) {
-        *err = "Unable to find UID for '" + args[1] + "': " + decode_uid_err;
+    auto uid = DecodeUid(args[1]);
+    if (!uid) {
+        *err = "Unable to find UID for '" + args[1] + "': " + uid.error();
         return false;
     }
+    uid_ = *uid;
     return true;
 }
 
@@ -979,34 +983,35 @@
     if (command_arg > 2 && args[1] != "-") {
         seclabel = args[1];
     }
-    uid_t uid = 0;
+    Result<uid_t> uid = 0;
     if (command_arg > 3) {
-        std::string decode_uid_err;
-        if (!DecodeUid(args[2], &uid, &decode_uid_err)) {
-            LOG(ERROR) << "Unable to find UID for '" << args[2] << "': " << decode_uid_err;
+        uid = DecodeUid(args[2]);
+        if (!uid) {
+            LOG(ERROR) << "Unable to decode UID for '" << args[2] << "': " << uid.error();
             return nullptr;
         }
     }
-    gid_t gid = 0;
+    Result<gid_t> gid = 0;
     std::vector<gid_t> supp_gids;
     if (command_arg > 4) {
-        std::string decode_uid_err;
-        if (!DecodeUid(args[3], &gid, &decode_uid_err)) {
-            LOG(ERROR) << "Unable to find GID for '" << args[3] << "': " << decode_uid_err;
+        gid = DecodeUid(args[3]);
+        if (!gid) {
+            LOG(ERROR) << "Unable to decode GID for '" << args[3] << "': " << gid.error();
             return nullptr;
         }
         std::size_t nr_supp_gids = command_arg - 1 /* -- */ - 4 /* exec SECLABEL UID GID */;
         for (size_t i = 0; i < nr_supp_gids; ++i) {
-            gid_t supp_gid;
-            if (!DecodeUid(args[4 + i], &supp_gid, &decode_uid_err)) {
-                LOG(ERROR) << "Unable to find UID for '" << args[4 + i] << "': " << decode_uid_err;
+            auto supp_gid = DecodeUid(args[4 + i]);
+            if (!supp_gid) {
+                LOG(ERROR) << "Unable to decode GID for '" << args[4 + i]
+                           << "': " << supp_gid.error();
                 return nullptr;
             }
-            supp_gids.push_back(supp_gid);
+            supp_gids.push_back(*supp_gid);
         }
     }
 
-    return std::make_unique<Service>(name, flags, uid, gid, supp_gids, no_capabilities,
+    return std::make_unique<Service>(name, flags, *uid, *gid, supp_gids, no_capabilities,
                                      namespace_flags, seclabel, str_args);
 }
 
diff --git a/init/service_test.cpp b/init/service_test.cpp
index 62e46f4..98d876f 100644
--- a/init/service_test.cpp
+++ b/init/service_test.cpp
@@ -132,29 +132,29 @@
         ASSERT_EQ("", svc->seclabel());
     }
     if (uid) {
-        uid_t decoded_uid;
-        std::string err;
-        ASSERT_TRUE(DecodeUid("log", &decoded_uid, &err));
-        ASSERT_EQ(decoded_uid, svc->uid());
+        auto decoded_uid = DecodeUid("log");
+        ASSERT_TRUE(decoded_uid);
+        ASSERT_EQ(*decoded_uid, svc->uid());
     } else {
         ASSERT_EQ(0U, svc->uid());
     }
     if (gid) {
-        uid_t decoded_uid;
-        std::string err;
-        ASSERT_TRUE(DecodeUid("shell", &decoded_uid, &err));
-        ASSERT_EQ(decoded_uid, svc->gid());
+        auto decoded_uid = DecodeUid("shell");
+        ASSERT_TRUE(decoded_uid);
+        ASSERT_EQ(*decoded_uid, svc->gid());
     } else {
         ASSERT_EQ(0U, svc->gid());
     }
     if (supplementary_gids) {
         ASSERT_EQ(2U, svc->supp_gids().size());
-        uid_t decoded_uid;
-        std::string err;
-        ASSERT_TRUE(DecodeUid("system", &decoded_uid, &err));
-        ASSERT_EQ(decoded_uid, svc->supp_gids()[0]);
-        ASSERT_TRUE(DecodeUid("adb", &decoded_uid, &err));
-        ASSERT_EQ(decoded_uid, svc->supp_gids()[1]);
+
+        auto decoded_uid = DecodeUid("system");
+        ASSERT_TRUE(decoded_uid);
+        ASSERT_EQ(*decoded_uid, svc->supp_gids()[0]);
+
+        decoded_uid = DecodeUid("adb");
+        ASSERT_TRUE(decoded_uid);
+        ASSERT_EQ(*decoded_uid, svc->supp_gids()[1]);
     } else {
         ASSERT_EQ(0U, svc->supp_gids().size());
     }
diff --git a/init/util.cpp b/init/util.cpp
index e037987..fcf7ca8 100644
--- a/init/util.cpp
+++ b/init/util.cpp
@@ -57,30 +57,20 @@
 const std::string kDefaultAndroidDtDir("/proc/device-tree/firmware/android/");
 
 // DecodeUid() - decodes and returns the given string, which can be either the
-// numeric or name representation, into the integer uid or gid. Returns
-// UINT_MAX on error.
-bool DecodeUid(const std::string& name, uid_t* uid, std::string* err) {
-    *uid = UINT_MAX;
-    *err = "";
-
+// numeric or name representation, into the integer uid or gid.
+Result<uid_t> DecodeUid(const std::string& name) {
     if (isalpha(name[0])) {
         passwd* pwd = getpwnam(name.c_str());
-        if (!pwd) {
-            *err = "getpwnam failed: "s + strerror(errno);
-            return false;
-        }
-        *uid = pwd->pw_uid;
-        return true;
+        if (!pwd) return ErrnoError() << "getpwnam failed";
+
+        return pwd->pw_uid;
     }
 
     errno = 0;
     uid_t result = static_cast<uid_t>(strtoul(name.c_str(), 0, 0));
-    if (errno) {
-        *err = "strtoul failed: "s + strerror(errno);
-        return false;
-    }
-    *uid = result;
-    return true;
+    if (errno) return ErrnoError() << "strtoul failed";
+
+    return result;
 }
 
 /*
@@ -164,50 +154,40 @@
     return -1;
 }
 
-bool ReadFile(const std::string& path, std::string* content, std::string* err) {
-    content->clear();
-    *err = "";
-
+Result<std::string> ReadFile(const std::string& path) {
     android::base::unique_fd fd(
         TEMP_FAILURE_RETRY(open(path.c_str(), O_RDONLY | O_NOFOLLOW | O_CLOEXEC)));
     if (fd == -1) {
-        *err = "Unable to open '" + path + "': " + strerror(errno);
-        return false;
+        return ErrnoError() << "open() failed";
     }
 
     // For security reasons, disallow world-writable
     // or group-writable files.
     struct stat sb;
     if (fstat(fd, &sb) == -1) {
-        *err = "fstat failed for '" + path + "': " + strerror(errno);
-        return false;
+        return ErrnoError() << "fstat failed()";
     }
     if ((sb.st_mode & (S_IWGRP | S_IWOTH)) != 0) {
-        *err = "Skipping insecure file '" + path + "'";
-        return false;
+        return Error() << "Skipping insecure file";
     }
 
-    if (!android::base::ReadFdToString(fd, content)) {
-        *err = "Unable to read '" + path + "': " + strerror(errno);
-        return false;
+    std::string content;
+    if (!android::base::ReadFdToString(fd, &content)) {
+        return ErrnoError() << "Unable to read file contents";
     }
-    return true;
+    return content;
 }
 
-bool WriteFile(const std::string& path, const std::string& content, std::string* err) {
-    *err = "";
-
+Result<Success> WriteFile(const std::string& path, const std::string& content) {
     android::base::unique_fd fd(TEMP_FAILURE_RETRY(
         open(path.c_str(), O_WRONLY | O_CREAT | O_NOFOLLOW | O_TRUNC | O_CLOEXEC, 0600)));
     if (fd == -1) {
-        *err = "Unable to open '" + path + "': " + strerror(errno);
-        return false;
+        return ErrnoError() << "open() failed";
     }
     if (!android::base::WriteStringToFd(content, fd)) {
-        *err = "Unable to write to '" + path + "': " + strerror(errno);
-        return false;
+        return ErrnoError() << "Unable to write file contents";
     }
-    return true;
+    return Success();
 }
 
 bool mkdir_recursive(const std::string& path, mode_t mode) {
diff --git a/init/util.h b/init/util.h
index a81df47..298aa1c 100644
--- a/init/util.h
+++ b/init/util.h
@@ -28,6 +28,8 @@
 #include <android-base/chrono_utils.h>
 #include <selinux/label.h>
 
+#include "result.h"
+
 #define COLDBOOT_DONE "/dev/.coldboot_done"
 
 using android::base::boot_clock;
@@ -39,10 +41,10 @@
 int CreateSocket(const char* name, int type, bool passcred, mode_t perm, uid_t uid, gid_t gid,
                  const char* socketcon);
 
-bool ReadFile(const std::string& path, std::string* content, std::string* err);
-bool WriteFile(const std::string& path, const std::string& content, std::string* err);
+Result<std::string> ReadFile(const std::string& path);
+Result<Success> WriteFile(const std::string& path, const std::string& content);
 
-bool DecodeUid(const std::string& name, uid_t* uid, std::string* err);
+Result<uid_t> DecodeUid(const std::string& name);
 
 bool mkdir_recursive(const std::string& pathname, mode_t mode);
 int wait_for_file(const char *filename, std::chrono::nanoseconds timeout);
diff --git a/init/util_test.cpp b/init/util_test.cpp
index 5dd271c..007d10e 100644
--- a/init/util_test.cpp
+++ b/init/util_test.cpp
@@ -30,61 +30,51 @@
 namespace init {
 
 TEST(util, ReadFile_ENOENT) {
-    std::string s("hello");
-    std::string err;
     errno = 0;
-    EXPECT_FALSE(ReadFile("/proc/does-not-exist", &s, &err));
-    EXPECT_EQ("Unable to open '/proc/does-not-exist': No such file or directory", err);
+    auto file_contents = ReadFile("/proc/does-not-exist");
     EXPECT_EQ(ENOENT, errno);
-    EXPECT_EQ("", s);  // s was cleared.
+    ASSERT_FALSE(file_contents);
+    EXPECT_EQ("open() failed: No such file or directory", file_contents.error());
 }
 
 TEST(util, ReadFileGroupWriteable) {
     std::string s("hello");
     TemporaryFile tf;
-    std::string err;
     ASSERT_TRUE(tf.fd != -1);
-    EXPECT_TRUE(WriteFile(tf.path, s, &err)) << strerror(errno);
-    EXPECT_EQ("", err);
+    EXPECT_TRUE(WriteFile(tf.path, s)) << strerror(errno);
     EXPECT_NE(-1, fchmodat(AT_FDCWD, tf.path, 0620, AT_SYMLINK_NOFOLLOW)) << strerror(errno);
-    EXPECT_FALSE(ReadFile(tf.path, &s, &err)) << strerror(errno);
-    EXPECT_EQ("Skipping insecure file '"s + tf.path + "'", err);
-    EXPECT_EQ("", s);  // s was cleared.
+    auto file_contents = ReadFile(tf.path);
+    ASSERT_FALSE(file_contents) << strerror(errno);
+    EXPECT_EQ("Skipping insecure file", file_contents.error());
 }
 
 TEST(util, ReadFileWorldWiteable) {
     std::string s("hello");
     TemporaryFile tf;
-    std::string err;
     ASSERT_TRUE(tf.fd != -1);
-    EXPECT_TRUE(WriteFile(tf.path, s, &err)) << strerror(errno);
-    EXPECT_EQ("", err);
+    EXPECT_TRUE(WriteFile(tf.path, s)) << strerror(errno);
     EXPECT_NE(-1, fchmodat(AT_FDCWD, tf.path, 0602, AT_SYMLINK_NOFOLLOW)) << strerror(errno);
-    EXPECT_FALSE(ReadFile(tf.path, &s, &err)) << strerror(errno);
-    EXPECT_EQ("Skipping insecure file '"s + tf.path + "'", err);
-    EXPECT_EQ("", s);  // s was cleared.
+    auto file_contents = ReadFile(tf.path);
+    ASSERT_FALSE(file_contents) << strerror(errno);
+    EXPECT_EQ("Skipping insecure file", file_contents.error());
 }
 
 TEST(util, ReadFileSymbolicLink) {
-    std::string s("hello");
     errno = 0;
     // lrwxrwxrwx 1 root root 13 1970-01-01 00:00 charger -> /sbin/healthd
-    std::string err;
-    EXPECT_FALSE(ReadFile("/charger", &s, &err));
-    EXPECT_EQ("Unable to open '/charger': Too many symbolic links encountered", err);
+    auto file_contents = ReadFile("/charger");
     EXPECT_EQ(ELOOP, errno);
-    EXPECT_EQ("", s);  // s was cleared.
+    ASSERT_FALSE(file_contents);
+    EXPECT_EQ("open() failed: Too many symbolic links encountered", file_contents.error());
 }
 
 TEST(util, ReadFileSuccess) {
-    std::string s("hello");
-    std::string err;
-    EXPECT_TRUE(ReadFile("/proc/version", &s, &err));
-    EXPECT_EQ("", err);
-    EXPECT_GT(s.length(), 6U);
-    EXPECT_EQ('\n', s[s.length() - 1]);
-    s[5] = 0;
-    EXPECT_STREQ("Linux", s.c_str());
+    auto file_contents = ReadFile("/proc/version");
+    ASSERT_TRUE(file_contents);
+    EXPECT_GT(file_contents->length(), 6U);
+    EXPECT_EQ('\n', file_contents->at(file_contents->length() - 1));
+    (*file_contents)[5] = 0;
+    EXPECT_STREQ("Linux", file_contents->c_str());
 }
 
 TEST(util, WriteFileBinary) {
@@ -95,29 +85,23 @@
     ASSERT_EQ(10u, contents.size());
 
     TemporaryFile tf;
-    std::string err;
     ASSERT_TRUE(tf.fd != -1);
-    EXPECT_TRUE(WriteFile(tf.path, contents, &err)) << strerror(errno);
-    EXPECT_EQ("", err);
+    EXPECT_TRUE(WriteFile(tf.path, contents)) << strerror(errno);
 
-    std::string read_back_contents;
-    EXPECT_TRUE(ReadFile(tf.path, &read_back_contents, &err)) << strerror(errno);
-    EXPECT_EQ("", err);
-    EXPECT_EQ(contents, read_back_contents);
-    EXPECT_EQ(10u, read_back_contents.size());
+    auto read_back_contents = ReadFile(tf.path);
+    ASSERT_TRUE(read_back_contents) << strerror(errno);
+    EXPECT_EQ(contents, *read_back_contents);
+    EXPECT_EQ(10u, read_back_contents->size());
 }
 
 TEST(util, WriteFileNotExist) {
     std::string s("hello");
-    std::string s2("hello");
     TemporaryDir test_dir;
     std::string path = android::base::StringPrintf("%s/does-not-exist", test_dir.path);
-    std::string err;
-    EXPECT_TRUE(WriteFile(path, s, &err));
-    EXPECT_EQ("", err);
-    EXPECT_TRUE(ReadFile(path, &s2, &err));
-    EXPECT_EQ("", err);
-    EXPECT_EQ(s, s2);
+    EXPECT_TRUE(WriteFile(path, s));
+    auto file_contents = ReadFile(path);
+    ASSERT_TRUE(file_contents);
+    EXPECT_EQ(s, *file_contents);
     struct stat sb;
     int fd = open(path.c_str(), O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
     EXPECT_NE(-1, fd);
@@ -127,37 +111,30 @@
 }
 
 TEST(util, WriteFileExist) {
-    std::string s2("");
     TemporaryFile tf;
     ASSERT_TRUE(tf.fd != -1);
-    std::string err;
-    EXPECT_TRUE(WriteFile(tf.path, "1hello1", &err)) << strerror(errno);
-    EXPECT_EQ("", err);
-    EXPECT_TRUE(ReadFile(tf.path, &s2, &err));
-    EXPECT_EQ("", err);
-    EXPECT_STREQ("1hello1", s2.c_str());
-    EXPECT_TRUE(WriteFile(tf.path, "2ll2", &err));
-    EXPECT_EQ("", err);
-    EXPECT_TRUE(ReadFile(tf.path, &s2, &err));
-    EXPECT_EQ("", err);
-    EXPECT_STREQ("2ll2", s2.c_str());
+    EXPECT_TRUE(WriteFile(tf.path, "1hello1")) << strerror(errno);
+    auto file_contents = ReadFile(tf.path);
+    ASSERT_TRUE(file_contents);
+    EXPECT_EQ("1hello1", *file_contents);
+    EXPECT_TRUE(WriteFile(tf.path, "2ll2"));
+    file_contents = ReadFile(tf.path);
+    ASSERT_TRUE(file_contents);
+    EXPECT_EQ("2ll2", *file_contents);
 }
 
 TEST(util, DecodeUid) {
-    uid_t decoded_uid;
-    std::string err;
+    auto decoded_uid = DecodeUid("root");
+    EXPECT_TRUE(decoded_uid);
+    EXPECT_EQ(0U, *decoded_uid);
 
-    EXPECT_TRUE(DecodeUid("root", &decoded_uid, &err));
-    EXPECT_EQ("", err);
-    EXPECT_EQ(0U, decoded_uid);
+    decoded_uid = DecodeUid("toot");
+    EXPECT_FALSE(decoded_uid);
+    EXPECT_EQ("getpwnam failed: No such file or directory", decoded_uid.error());
 
-    EXPECT_FALSE(DecodeUid("toot", &decoded_uid, &err));
-    EXPECT_EQ("getpwnam failed: No such file or directory", err);
-    EXPECT_EQ(UINT_MAX, decoded_uid);
-
-    EXPECT_TRUE(DecodeUid("123", &decoded_uid, &err));
-    EXPECT_EQ("", err);
-    EXPECT_EQ(123U, decoded_uid);
+    decoded_uid = DecodeUid("123");
+    EXPECT_TRUE(decoded_uid);
+    EXPECT_EQ(123U, *decoded_uid);
 }
 
 TEST(util, is_dir) {