cat: Use ArgumentParser

C++ was being naughty and implicitly casting our fallback const char* to a boolean.

apps/CMakeLists.txt

@@ -7,9 +7,11 @@ function(luna_app SOURCE_FILE APP_NAME)
 endfunction()
 
 luna_app(init.cpp init)
-luna_app(cat.cpp cat)
 luna_app(sh.cpp sh)
 
+luna_app(cat.cpp cat)
+target_link_libraries(cat PRIVATE os)
+
 luna_app(date.cpp date)
 target_link_libraries(date PRIVATE os)
 

apps/cat.cpp

@@ -1,9 +1,24 @@
+#include <os/ArgumentParser.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
-static void do_cat(FILE* f)
+static void do_cat(StringView path)
 {
+    FILE* f;
+
+    if (path == "-") f = stdin;
+    else
+    {
+        f = fopen(path.chars(), "r");
+        if (!f)
+        {
+            perror(path.chars());
+            exit(1);
+        }
+    }
+
     char buffer[4096];
 
     while (1)
@@ -12,30 +27,19 @@ static void do_cat(FILE* f)
         if (nread == 0) return;
         fwrite(buffer, 1, nread, stdout);
     }
+
+    if (f != stdin) fclose(f);
 }
 
 int main(int argc, char** argv)
 {
-    FILE* f;
+    StringView filename;
 
-    if (argc < 2) { do_cat(stdin); }
-    else
-    {
-        for (int i = 1; i < argc; i++)
-        {
-            if (!strcmp(argv[i], "-")) f = stdin;
-            else
-            {
-                f = fopen(argv[i], "r");
-                if (!f)
-                {
-                    perror(argv[i]);
-                    return 1;
-                }
-            }
+    ArgumentParser parser;
+    parser.add_positional_argument(filename, "file"_sv, "-"_sv);
+    Vector<StringView> extra_files = parser.parse(argc, argv).value();
 
-            do_cat(f);
-            if (f != stdin) fclose(f);
-        }
-    }
+    do_cat(filename);
+
+    for (auto file : extra_files) { do_cat(file); }
 }

apps/date.cpp

@@ -10,7 +10,7 @@ int main(int argc, char** argv)
     StringView date;
 
     ArgumentParser parser;
-    parser.add_value_argument(date, 'd', "date", false);
+    parser.add_value_argument(date, 'd', "date"_sv, false);
     parser.parse(argc, argv);
 
     time_t now;

apps/edit.cpp

@@ -10,7 +10,7 @@ int main(int argc, char** argv)
     StringView pathname;
 
     ArgumentParser parser;
-    parser.add_positional_argument(pathname, "file", true);
+    parser.add_positional_argument(pathname, "file"_sv, true);
     parser.parse(argc, argv);
 
     f = fopen(pathname.chars(), "w");

apps/ls.cpp

@@ -12,9 +12,9 @@ int main(int argc, char** argv)
     bool show_almost_all;
 
     ArgumentParser parser;
-    parser.add_positional_argument(pathname, "directory", "/");
-    parser.add_switch_argument(show_all, 'a', "all");
-    parser.add_switch_argument(show_almost_all, 'A', "almost-all");
+    parser.add_positional_argument(pathname, "directory"_sv, "/"_sv);
+    parser.add_switch_argument(show_all, 'a', "all"_sv);
+    parser.add_switch_argument(show_almost_all, 'A', "almost-all"_sv);
     parser.parse(argc, argv);
 
     DIR* dp = opendir(pathname.chars());

libluna/include/luna/StringView.h

@@ -52,3 +52,13 @@ class StringView
 
     usize m_length { 0 };
 };
+
+inline StringView operator""_sv(const char* cstring)
+{
+    return StringView { cstring };
+}
+
+inline StringView operator""_sv(const char* cstring, usize length)
+{
+    return StringView { cstring, length };
+}

libos/include/os/ArgumentParser.h

@@ -15,7 +15,7 @@ class ArgumentParser
     Result<void> add_value_argument(StringView& out, char short_flag, StringView long_flag, bool value_required);
     Result<void> add_value_argument(StringView& out, char short_flag, StringView long_flag, StringView fallback);
 
-    void parse(int argc, char* const* argv);
+    Result<Vector<StringView>> parse(int argc, char* const* argv);
 
   private:
     struct PositionalArgument

libos/src/ArgumentParser.cpp

@@ -49,10 +49,12 @@ static bool looks_like_long_flag(StringView arg)
     return arg.length() > 2 && arg[0] == '-' && arg[1] == '-';
 }
 
-void ArgumentParser::parse(int argc, char* const* argv)
+Result<Vector<StringView>> ArgumentParser::parse(int argc, char* const* argv)
 {
     StringView program_name = argv[0];
 
+    Vector<StringView> leftovers;
+
     Option<ValueArgument> current_value_argument = {};
     bool is_parsing_value_argument = false;
 
@@ -144,7 +146,7 @@ void ArgumentParser::parse(int argc, char* const* argv)
         Option<PositionalArgument> current = m_positional_args.try_dequeue();
         if (!current.has_value())
         {
-            fprintf(stderr, "%s: unused argument '%s'\n", program_name.chars(), arg.chars());
+            TRY(leftovers.try_append(arg));
             continue;
         }
 
@@ -172,4 +174,6 @@ void ArgumentParser::parse(int argc, char* const* argv)
         }
         else { *arg.out = arg.fallback; }
     }
+
+    return leftovers;
 }