diff --git a/init/builtins.cpp b/init/builtins.cpp
index 3dadfd7..27b72f9 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -150,7 +150,12 @@
 }
 
 static int do_domainname(const std::vector<std::string>& args) {
-    return write_file("/proc/sys/kernel/domainname", args[1]) ? 0 : 1;
+    std::string err;
+    if (!WriteFile("/proc/sys/kernel/domainname", args[1], &err)) {
+        LOG(ERROR) << err;
+        return -1;
+    }
+    return 0;
 }
 
 static int do_enable(const std::vector<std::string>& args) {
@@ -174,7 +179,12 @@
 }
 
 static int do_hostname(const std::vector<std::string>& args) {
-    return write_file("/proc/sys/kernel/hostname", args[1]) ? 0 : 1;
+    std::string err;
+    if (!WriteFile("/proc/sys/kernel/hostname", args[1], &err)) {
+        LOG(ERROR) << err;
+        return -1;
+    }
+    return 0;
 }
 
 static int do_ifup(const std::vector<std::string>& args) {
@@ -215,11 +225,19 @@
     }
 
     if (args.size() >= 4) {
-        uid_t uid = decode_uid(args[3].c_str());
+        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;
+            return -1;
+        }
         gid_t gid = -1;
 
         if (args.size() == 5) {
-            gid = decode_uid(args[4].c_str());
+            if (!DecodeUid(args[4], &gid, &decode_uid_err)) {
+                LOG(ERROR) << "Unable to find GID for '" << args[3] << "': " << decode_uid_err;
+                return -1;
+            }
         }
 
         if (lchown(args[1].c_str(), uid, gid) == -1) {
@@ -643,29 +661,49 @@
 }
 
 static int do_write(const std::vector<std::string>& args) {
-    return write_file(args[1], args[2]) ? 0 : 1;
+    std::string err;
+    if (!WriteFile(args[1], args[2], &err)) {
+        LOG(ERROR) << err;
+        return -1;
+    }
+    return 0;
 }
 
 static int do_copy(const std::vector<std::string>& args) {
     std::string data;
-    if (read_file(args[1], &data)) {
-        return write_file(args[2], data) ? 0 : 1;
+    std::string err;
+    if (!ReadFile(args[1], &data, &err)) {
+        LOG(ERROR) << err;
+        return -1;
     }
-    return 1;
+    if (!WriteFile(args[2], data, &err)) {
+        LOG(ERROR) << err;
+        return -1;
+    }
+    return 0;
 }
 
 static int do_chown(const std::vector<std::string>& args) {
-    /* GID is optional. */
-    if (args.size() == 3) {
-        if (lchown(args[2].c_str(), decode_uid(args[1].c_str()), -1) == -1)
-            return -errno;
-    } else if (args.size() == 4) {
-        if (lchown(args[3].c_str(), decode_uid(args[1].c_str()),
-                   decode_uid(args[2].c_str())) == -1)
-            return -errno;
-    } else {
+    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;
         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;
+
+    if (args.size() == 4) {
+        if (!DecodeUid(args[2], &gid, &decode_uid_err)) {
+            LOG(ERROR) << "Unable to find GID for '" << args[2] << "': " << decode_uid_err;
+            return -1;
+        }
+    }
+
+    if (lchown(path.c_str(), uid, gid) == -1) return -errno;
+
     return 0;
 }
 
diff --git a/init/init.cpp b/init/init.cpp
index e7d01f4..6de2061 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -871,7 +871,9 @@
             }
         }
 
-        if (!write_file("/sys/fs/selinux/checkreqprot", "0")) {
+        std::string err;
+        if (!WriteFile("/sys/fs/selinux/checkreqprot", "0", &err)) {
+            LOG(ERROR) << err;
             security_failure();
         }
 
diff --git a/init/init_parser.cpp b/init/init_parser.cpp
index 620367a..1b31cf2 100644
--- a/init/init_parser.cpp
+++ b/init/init_parser.cpp
@@ -110,7 +110,9 @@
     LOG(INFO) << "Parsing file " << path << "...";
     Timer t;
     std::string data;
-    if (!read_file(path, &data)) {
+    std::string err;
+    if (!ReadFile(path, &data, &err)) {
+        LOG(ERROR) << err;
         return false;
     }
 
diff --git a/init/init_parser_test.cpp b/init/init_parser_test.cpp
index d8fd2ba..86d60d0 100644
--- a/init/init_parser_test.cpp
+++ b/init/init_parser_test.cpp
@@ -86,19 +86,29 @@
         ASSERT_EQ("", svc->seclabel());
     }
     if (uid) {
-        ASSERT_EQ(decode_uid("log"), svc->uid());
+        uid_t decoded_uid;
+        std::string err;
+        ASSERT_TRUE(DecodeUid("log", &decoded_uid, &err));
+        ASSERT_EQ(decoded_uid, svc->uid());
     } else {
         ASSERT_EQ(0U, svc->uid());
     }
     if (gid) {
-        ASSERT_EQ(decode_uid("shell"), svc->gid());
+        uid_t decoded_uid;
+        std::string err;
+        ASSERT_TRUE(DecodeUid("shell", &decoded_uid, &err));
+        ASSERT_EQ(decoded_uid, svc->gid());
     } else {
         ASSERT_EQ(0U, svc->gid());
     }
     if (supplementary_gids) {
         ASSERT_EQ(2U, svc->supp_gids().size());
-        ASSERT_EQ(decode_uid("system"), svc->supp_gids()[0]);
-        ASSERT_EQ(decode_uid("adb"), svc->supp_gids()[1]);
+        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]);
     } else {
         ASSERT_EQ(0U, svc->supp_gids().size());
     }
diff --git a/init/init_test.cpp b/init/init_test.cpp
index 3da14b5..7093ba9 100644
--- a/init/init_test.cpp
+++ b/init/init_test.cpp
@@ -152,10 +152,11 @@
                                "on boot\n"
                                "execute 3";
     // clang-format on
-    // write_file() ensures the right mode is set
-    ASSERT_TRUE(write_file(std::string(dir.path) + "/a.rc", dir_a_script));
+    // 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(write_file(std::string(dir.path) + "/b.rc", "on boot\nexecute 5"));
+    ASSERT_TRUE(WriteFile(std::string(dir.path) + "/b.rc", "on boot\nexecute 5", &err));
 
     // clang-format off
     std::string start_script = "import " + std::string(first_import.path) + "\n"
diff --git a/init/property_service.cpp b/init/property_service.cpp
index 6f40d1c..e01cd0b 100644
--- a/init/property_service.cpp
+++ b/init/property_service.cpp
@@ -510,8 +510,9 @@
 static void load_properties_from_file(const char* filename, const char* filter) {
     Timer t;
     std::string data;
-    if (!read_file(filename, &data)) {
-        PLOG(WARNING) << "Couldn't load properties from " << filename;
+    std::string err;
+    if (!ReadFile(filename, &data, &err)) {
+        PLOG(WARNING) << "Couldn't load property file: " << err;
         return;
     }
     data.push_back('\n');
diff --git a/init/service.cpp b/init/service.cpp
index 3a9f622..4d9edc4 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -380,9 +380,18 @@
 }
 
 bool Service::ParseGroup(const std::vector<std::string>& args, std::string* err) {
-    gid_ = decode_uid(args[1].c_str());
+    std::string decode_uid_err;
+    if (!DecodeUid(args[1], &gid_, &decode_uid_err)) {
+        *err = "Unable to find GID for '" + args[1] + "': " + decode_uid_err;
+        return false;
+    }
     for (std::size_t n = 2; n < args.size(); n++) {
-        supp_gids_.emplace_back(decode_uid(args[n].c_str()));
+        gid_t gid;
+        if (!DecodeUid(args[n], &gid, &decode_uid_err)) {
+            *err = "Unable to find GID for '" + args[n] + "': " + decode_uid_err;
+            return false;
+        }
+        supp_gids_.emplace_back(gid);
     }
     return true;
 }
@@ -480,10 +489,25 @@
 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 = args.size() > 4 ? decode_uid(args[4].c_str()) : 0;
-    gid_t gid = args.size() > 5 ? decode_uid(args[5].c_str()) : 0;
+    uid_t uid = 0;
+    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;
+            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;
+            return false;
+        }
+    }
+
     auto descriptor = std::make_unique<T>(args[1], args[2], uid, gid, perm, context);
 
     auto old =
@@ -522,7 +546,11 @@
 }
 
 bool Service::ParseUser(const std::vector<std::string>& args, std::string* err) {
-    uid_ = decode_uid(args[1].c_str());
+    std::string decode_uid_err;
+    if (!DecodeUid(args[1], &uid_, &decode_uid_err)) {
+        *err = "Unable to find UID for '" + args[1] + "': " + decode_uid_err;
+        return false;
+    }
     return true;
 }
 
@@ -936,15 +964,28 @@
     }
     uid_t uid = 0;
     if (command_arg > 3) {
-        uid = decode_uid(args[2].c_str());
+        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;
+            return nullptr;
+        }
     }
     gid_t gid = 0;
     std::vector<gid_t> supp_gids;
     if (command_arg > 4) {
-        gid = decode_uid(args[3].c_str());
+        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;
+            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) {
-            supp_gids.push_back(decode_uid(args[4 + i].c_str()));
+            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;
+                return nullptr;
+            }
+            supp_gids.push_back(supp_gid);
         }
     }
 
diff --git a/init/util.cpp b/init/util.cpp
index 87b8d9d..e7f724b 100644
--- a/init/util.cpp
+++ b/init/util.cpp
@@ -48,39 +48,33 @@
 #endif
 
 using android::base::boot_clock;
+using namespace std::literals::string_literals;
 
-static unsigned int do_decode_uid(const char *s)
-{
-    unsigned int v;
+// 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 = "";
 
-    if (!s || *s == '\0')
-        return UINT_MAX;
-
-    if (isalpha(s[0])) {
-        struct passwd* pwd = getpwnam(s);
-        if (!pwd)
-            return UINT_MAX;
-        return pwd->pw_uid;
+    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;
     }
 
     errno = 0;
-    v = (unsigned int) strtoul(s, 0, 0);
-    if (errno)
-        return UINT_MAX;
-    return v;
-}
-
-/*
- * decode_uid - 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.
- */
-unsigned int decode_uid(const char *s) {
-    unsigned int v = do_decode_uid(s);
-    if (v == UINT_MAX) {
-        LOG(ERROR) << "decode_uid: Unable to find UID for '" << s << "'; returning UINT_MAX";
+    uid_t result = static_cast<uid_t>(strtoul(name.c_str(), 0, 0));
+    if (errno) {
+        *err = "strtoul failed: "s + strerror(errno);
+        return false;
     }
-    return v;
+    *uid = result;
+    return true;
 }
 
 /*
@@ -157,12 +151,14 @@
     return -1;
 }
 
-bool read_file(const std::string& path, std::string* content) {
+bool ReadFile(const std::string& path, std::string* content, std::string* err) {
     content->clear();
+    *err = "";
 
     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;
     }
 
@@ -170,29 +166,35 @@
     // or group-writable files.
     struct stat sb;
     if (fstat(fd, &sb) == -1) {
-        PLOG(ERROR) << "fstat failed for '" << path << "'";
+        *err = "fstat failed for '" + path + "': " + strerror(errno);
         return false;
     }
     if ((sb.st_mode & (S_IWGRP | S_IWOTH)) != 0) {
-        LOG(ERROR) << "skipping insecure file '" << path << "'";
+        *err = "Skipping insecure file '" + path + "'";
         return false;
     }
 
-    return android::base::ReadFdToString(fd, content);
+    if (!android::base::ReadFdToString(fd, content)) {
+        *err = "Unable to read '" + path + "': " + strerror(errno);
+        return false;
+    }
+    return true;
 }
 
-bool write_file(const std::string& path, const std::string& content) {
+bool WriteFile(const std::string& path, const std::string& content, std::string* err) {
+    *err = "";
+
     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) {
-        PLOG(ERROR) << "write_file: Unable to open '" << path << "'";
+        *err = "Unable to open '" + path + "': " + strerror(errno);
         return false;
     }
-    bool success = android::base::WriteStringToFd(content, fd);
-    if (!success) {
-        PLOG(ERROR) << "write_file: Unable to write to '" << path << "'";
+    if (!android::base::WriteStringToFd(content, fd)) {
+        *err = "Unable to write to '" + path + "': " + strerror(errno);
+        return false;
     }
-    return success;
+    return true;
 }
 
 int mkdir_recursive(const std::string& path, mode_t mode, selabel_handle* sehandle) {
diff --git a/init/util.h b/init/util.h
index 55ebded..4c33909 100644
--- a/init/util.h
+++ b/init/util.h
@@ -38,8 +38,8 @@
 int create_socket(const char* name, int type, mode_t perm, uid_t uid, gid_t gid,
                   const char* socketcon, selabel_handle* sehandle);
 
-bool read_file(const std::string& path, std::string* content);
-bool write_file(const std::string& path, const std::string& content);
+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);
 
 class Timer {
   public:
@@ -61,7 +61,7 @@
 
 std::ostream& operator<<(std::ostream& os, const Timer& t);
 
-unsigned int decode_uid(const char *s);
+bool DecodeUid(const std::string& name, uid_t* uid, std::string* err);
 
 int mkdir_recursive(const std::string& pathname, mode_t mode, selabel_handle* sehandle);
 int wait_for_file(const char *filename, std::chrono::nanoseconds timeout);
diff --git a/init/util_test.cpp b/init/util_test.cpp
index ac23a32..4bb8a83 100644
--- a/init/util_test.cpp
+++ b/init/util_test.cpp
@@ -24,53 +24,67 @@
 #include <android-base/test_utils.h>
 #include <gtest/gtest.h>
 
-TEST(util, read_file_ENOENT) {
-  std::string s("hello");
-  errno = 0;
-  EXPECT_FALSE(read_file("/proc/does-not-exist", &s));
-  EXPECT_EQ(ENOENT, errno);
-  EXPECT_EQ("", s); // s was cleared.
+using namespace std::literals::string_literals;
+
+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);
+    EXPECT_EQ(ENOENT, errno);
+    EXPECT_EQ("", s);  // s was cleared.
 }
 
-TEST(util, read_file_group_writeable) {
+TEST(util, ReadFileGroupWriteable) {
     std::string s("hello");
     TemporaryFile tf;
+    std::string err;
     ASSERT_TRUE(tf.fd != -1);
-    EXPECT_TRUE(write_file(tf.path, s)) << strerror(errno);
+    EXPECT_TRUE(WriteFile(tf.path, s, &err)) << strerror(errno);
+    EXPECT_EQ("", err);
     EXPECT_NE(-1, fchmodat(AT_FDCWD, tf.path, 0620, AT_SYMLINK_NOFOLLOW)) << strerror(errno);
-    EXPECT_FALSE(read_file(tf.path, &s)) << 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.
 }
 
-TEST(util, read_file_world_writeable) {
+TEST(util, ReadFileWorldWiteable) {
     std::string s("hello");
     TemporaryFile tf;
+    std::string err;
     ASSERT_TRUE(tf.fd != -1);
-    EXPECT_TRUE(write_file(tf.path, s.c_str())) << strerror(errno);
+    EXPECT_TRUE(WriteFile(tf.path, s, &err)) << strerror(errno);
+    EXPECT_EQ("", err);
     EXPECT_NE(-1, fchmodat(AT_FDCWD, tf.path, 0602, AT_SYMLINK_NOFOLLOW)) << strerror(errno);
-    EXPECT_FALSE(read_file(tf.path, &s)) << 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.
 }
 
-TEST(util, read_file_symbolic_link) {
+TEST(util, ReadFileSymbolicLink) {
     std::string s("hello");
     errno = 0;
     // lrwxrwxrwx 1 root root 13 1970-01-01 00:00 charger -> /sbin/healthd
-    EXPECT_FALSE(read_file("/charger", &s));
+    std::string err;
+    EXPECT_FALSE(ReadFile("/charger", &s, &err));
+    EXPECT_EQ("Unable to open '/charger': Too many symbolic links encountered", err);
     EXPECT_EQ(ELOOP, errno);
     EXPECT_EQ("", s);  // s was cleared.
 }
 
-TEST(util, read_file_success) {
-  std::string s("hello");
-  EXPECT_TRUE(read_file("/proc/version", &s));
-  EXPECT_GT(s.length(), 6U);
-  EXPECT_EQ('\n', s[s.length() - 1]);
-  s[5] = 0;
-  EXPECT_STREQ("Linux", s.c_str());
+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());
 }
 
-TEST(util, write_file_binary) {
+TEST(util, WriteFileBinary) {
     std::string contents("abcd");
     contents.push_back('\0');
     contents.push_back('\0');
@@ -78,22 +92,28 @@
     ASSERT_EQ(10u, contents.size());
 
     TemporaryFile tf;
+    std::string err;
     ASSERT_TRUE(tf.fd != -1);
-    EXPECT_TRUE(write_file(tf.path, contents)) << strerror(errno);
+    EXPECT_TRUE(WriteFile(tf.path, contents, &err)) << strerror(errno);
+    EXPECT_EQ("", err);
 
     std::string read_back_contents;
-    EXPECT_TRUE(read_file(tf.path, &read_back_contents)) << strerror(errno);
+    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());
 }
 
-TEST(util, write_file_not_exist) {
+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);
-    EXPECT_TRUE(write_file(path, s));
-    EXPECT_TRUE(read_file(path, &s2));
+    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);
     struct stat sb;
     int fd = open(path.c_str(), O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
@@ -103,22 +123,38 @@
     EXPECT_EQ(0, unlink(path.c_str()));
 }
 
-TEST(util, write_file_exist) {
+TEST(util, WriteFileExist) {
     std::string s2("");
     TemporaryFile tf;
     ASSERT_TRUE(tf.fd != -1);
-    EXPECT_TRUE(write_file(tf.path, "1hello1")) << strerror(errno);
-    EXPECT_TRUE(read_file(tf.path, &s2));
+    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(write_file(tf.path, "2ll2"));
-    EXPECT_TRUE(read_file(tf.path, &s2));
+    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());
 }
 
-TEST(util, decode_uid) {
-  EXPECT_EQ(0U, decode_uid("root"));
-  EXPECT_EQ(UINT_MAX, decode_uid("toot"));
-  EXPECT_EQ(123U, decode_uid("123"));
+TEST(util, DecodeUid) {
+    uid_t decoded_uid;
+    std::string err;
+
+    EXPECT_TRUE(DecodeUid("root", &decoded_uid, &err));
+    EXPECT_EQ("", err);
+    EXPECT_EQ(0U, decoded_uid);
+
+    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);
 }
 
 TEST(util, is_dir) {