diff --git a/src/main.cpp b/src/main.cpp
index 1e999f3..effbdb0 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -2,11 +2,13 @@
 #include <cerrno>
 #include <iostream>
 #include <cstdlib>
+#include <iterator>
 #include <string>
 #include <stdexcept>
 #include <vector>
 #include <map>
 #include <algorithm>
+#include <set>
 
 // POSIX
 #include <getopt.h>
@@ -21,38 +23,40 @@
 // project
 #include "version.hpp"
 
-std::vector<std::string> additions;
-std::string change;
-std::map<std::string, std::string> changes;
-std::vector<std::string> deletions;
-bool should_list = false;
-bool sort = false;
+using namespace std;
 
-static void handle_additions(std::vector<std::string>& tags) {
-    for (const std::string& tag : additions) {
-        tags.push_back(tag);
-    }
+set<string> additions;
+string change;
+map<string, string> changes;
+vector<string> deletions;
+bool should_list = false;
+
+static void handle_additions(vector<string>& cur_tags) {
+    set<string> tags {cur_tags.begin(), cur_tags.end()};
+    tags.insert(additions.begin(), additions.end());
+    cur_tags.clear();
+    copy(tags.begin(), tags.end(), back_inserter(cur_tags));
 }
 
-static void handle_changes(std::vector<std::string>& tags) {
+static void handle_changes(vector<string>& tags) {
     for (const auto& elem : changes) {
-        auto it = std::find(tags.begin(), tags.end(), elem.first);
+        auto it = find(tags.begin(), tags.end(), elem.first);
         if (it != tags.end()) {
             *it = elem.second;
         }
     }
 }
 
-static void handle_deletions(std::vector<std::string>& tags) {
-    for (const std::string& tag : deletions) {
-        tags.erase(std::remove(tags.begin(), tags.end(), tag), tags.end());
+static void handle_deletions(vector<string>& tags) {
+    for (const string& tag : deletions) {
+        tags.erase(remove(tags.begin(), tags.end(), tag), tags.end());
     }
 }
 
 static void process(const char* path) {
     const char* tagname {"user.xdg.tags"};
-    std::vector<std::string> tags;
-    std::vector<char> buf(1024);
+    vector<string> tags;
+    vector<char> buf(1024);
     ssize_t sz = 0;
     do {
         sz = getxattr(path, tagname, buf.data(), buf.size());
@@ -67,41 +71,37 @@ static void process(const char* path) {
         }
     } while (sz == -1 && errno == ERANGE);
     if (sz > 0) {
-        std::string val(buf.data(), sz);
+        string val(buf.data(), sz);
         tags = sc::split(val, ",");
     }
     bool edits = additions.size() > 0 || changes.size() > 0 || deletions.size() > 0;
     if (edits) {
         if (should_list) {
-            std::cout << path << '\n';
-            std::cout << "  before: " << sc::io::greenf << sc::join(tags, ", ") << sc::io::reset << '\n';
+            cout << path << '\n';
+            cout << "  before: " << sc::io::greenf << sc::join(tags, ", ") << sc::io::reset << '\n';
         }
         handle_deletions(tags);
         handle_changes(tags);
         handle_additions(tags);
-        if (sort) {
-            std::sort(tags.begin(), tags.end());
-        }
         if (should_list) {
-            std::cout << "   after: " << sc::io::yellowf << sc::join(tags, ", ") << sc::io::reset << '\n';
+            cout << "   after: " << sc::io::yellowf << sc::join(tags, ", ") << sc::io::reset << '\n';
         }
-        std::string joined {sc::join(tags, ",")};
+        string joined {sc::join(tags, ",")};
         throw_if_min1(setxattr(path, tagname, joined.c_str(), joined.size(), 0));
     } else {
-        std::cout << path << ": " << sc::io::yellowf << sc::join(tags, ", ") << sc::io::reset << '\n';
+        cout << path << ": " << sc::io::yellowf << sc::join(tags, ", ") << sc::io::reset << '\n';
     }
 }
 
 static void print_help() {
-    std::cout << "usage: tagger [-h|--version] [-l] [-s] [-a tag] [-d tag] [-c tag -i tag] file...\n";
-    std::cout << "  -h, --help    show this help text and exit\n";
-    std::cout << "  --version     show version number and exit\n";
-    std::cout << "  -l, --list    list all tags\n";
-    std::cout << "  -s, --sort    write tags sorted alphabetically\n";
-    std::cout << "  -a, --add     add a tag\n";
-    std::cout << "  -d, --delete  delete a tag\n";
-    std::cout << "  -c, --change  change a tag\n";
-    std::cout << "  -i, --into    into new value\n";
+    cout << "usage: tagger [-h|--version] [-l] [-a tag] [-d tag] [-c tag -i tag] file...\n";
+    cout << "  -h, --help    show this help text and exit\n";
+    cout << "  --version     show version number and exit\n";
+    cout << "  -l, --list    list all tags\n";
+    cout << "  -a, --add     add a tag\n";
+    cout << "  -d, --delete  delete a tag\n";
+    cout << "  -c, --change  change a tag\n";
+    cout << "  -i, --into    into new value\n";
 }
 
 int main(int argc, char* argv[]) {
@@ -114,45 +114,43 @@ int main(int argc, char* argv[]) {
             {"help", no_argument, nullptr, 'h'},
             {"into", required_argument, nullptr, 'i'},
             {"list", no_argument, nullptr, 'l'},
-            {"sort", no_argument, nullptr, 's'},
             {"version", no_argument, &opt_val, 1},
             {nullptr, 0, nullptr, 0}
         };
-        while ((opt_char = getopt_long(argc, argv, "a:c:d:hi:ls", long_options, nullptr)) != -1) {
-            std::string arg {optarg ? optarg : ""};
+        while ((opt_char = getopt_long(argc, argv, "a:c:d:hi:l", long_options, nullptr)) != -1) {
+            string arg {optarg ? optarg : ""};
             switch (opt_char) {
                 case 0: {
                     // handle long-only options here
                     switch (opt_val) {
                         case 1:
-                            std::cout << tagger_version() << '\n';
+                            cout << tagger_version() << '\n';
                             return EXIT_SUCCESS;
                     }
                     break;
                 }
-                case 'a': additions.push_back(arg); break;
+                case 'a': additions.insert(arg); break;
                 case 'c': change = arg; break;
                 case 'd': deletions.push_back(arg); break;
                 case 'h': print_help(); return EXIT_SUCCESS;
                 case 'i': changes.emplace(change, arg); break;
                 case 'l': should_list = true; break;
-                case 's': sort = true; break;
-                case '?': throw std::runtime_error {"unrecognized option"};
+                case '?': throw runtime_error {"unrecognized option"};
             }
         }
         if (optind == argc) {
             // here when no file args
-            throw std::runtime_error {"please specify input files"};
+            throw runtime_error {"please specify input files"};
         }
         for (int i = optind; i < argc; ++i) {
             try {
                 process(argv[i]);
-            } catch (const std::runtime_error& ex) {
-                std::cerr << "tagger: " << ex.what() << '\n';
+            } catch (const runtime_error& ex) {
+                cerr << "tagger: " << ex.what() << '\n';
             }
         }
-    } catch (const std::exception& ex) {
-        std::cerr << "tagger: " << ex.what() << '\n';
+    } catch (const exception& ex) {
+        cerr << "tagger: " << ex.what() << '\n';
         return EXIT_FAILURE;
     }
     return EXIT_SUCCESS;