sh: Add a system to easily add flexible shell builtins

CMakeLists.txt

@@ -48,3 +48,4 @@ add_subdirectory(libc)
 add_subdirectory(kernel)
 add_subdirectory(apps)
 add_subdirectory(tests)
+add_subdirectory(shell)

apps/CMakeLists.txt

@@ -16,7 +16,6 @@ install(TARGETS preinit DESTINATION ${LUNA_ROOT}/initrd/bin)
 luna_app(init.cpp init)
 luna_app(env.cpp env)
 luna_app(su.cpp su)
-luna_app(sh.cpp sh)
 luna_app(cat.cpp cat)
 luna_app(date.cpp date)
 luna_app(edit.cpp edit)

libluna/include/luna/String.h

@@ -1,4 +1,5 @@
 #pragma once
+#include <luna/Hash.h>
 #include <luna/Result.h>
 #include <luna/StringView.h>
 #include <stdarg.h>
@@ -129,3 +130,5 @@ class String
 
     void empty();
 };
+
+template <> u64 hash(const String& value, u64 salt);

libluna/include/luna/StringView.h

@@ -1,4 +1,5 @@
 #pragma once
+#include <luna/Hash.h>
 #include <luna/Result.h>
 #include <luna/Vector.h>
 
@@ -75,3 +76,5 @@ inline StringView operator""_sv(const char* cstring, usize length)
 {
     return StringView { cstring, length };
 }
+
+template <> u64 hash(const StringView& value, u64 salt);

libluna/src/String.cpp

@@ -202,3 +202,8 @@ int String::compare(const String* a, const String* b)
 {
     return strcmp(a->chars(), b->chars());
 }
+
+template <> u64 hash(const String& value, u64 salt)
+{
+    return hash_memory(value.chars(), value.length(), salt);
+}

libluna/src/StringView.cpp

@@ -153,3 +153,8 @@ StringView StringView::from_fixed_size_cstring(const char* string, usize max)
 {
     return { string, strnlen(string, max) };
 }
+
+template <> u64 hash(const StringView& value, u64 salt)
+{
+    return hash_memory(value.chars(), value.length(), salt);
+}

libos/include/os/ArgumentParser.h

@@ -115,9 +115,10 @@ namespace os
          *
          * @param argc The argc value passed to main() or luna_main().
          * @param argv The argv value passed to main() or luna_main().
-         * @return Result<void> Whether the operation succeeded.
+         * @return Result<bool> Whether the operation succeeded, and if the arguments were correctly parsed (only needed
+         * if should_exit_on_bad_usage is not set, otherwise the success result would always be true).
          */
-        Result<void> parse(int argc, char* const* argv);
+        Result<bool> parse(int argc, char* const* argv);
 
         /**
          * @brief A program's copyright and version information.
@@ -155,13 +156,23 @@ namespace os
          *  "Try running '<program> -h' for more information." if -h has not been overridden.
          *  If both have been overridden, no output is shown.
          *
-         * Then, the program exits with a non-zero exit code.
+         * Then, the program exits with a non-zero exit code, if should_exit_on_bad_usage is set.
          * This function is designed to be used when the program detects an invalid argument value after parse() has run
          * successfully.
          *
          * @param program_name The program name to show (usually argv[0]).
          */
-        void short_usage(StringView program_name);
+        Result<void> short_usage(StringView program_name);
+
+        /**
+         * @brief Set whether the parser should exit the program when an incorrect usage is detected.
+         *
+         * @param b The boolean value to set.
+         */
+        void set_should_exit_on_bad_usage(bool b)
+        {
+            m_should_exit_on_bad_usage = b;
+        }
 
       private:
         struct PositionalArgument
@@ -190,7 +201,7 @@ namespace os
 
         Result<void> usage(StringView program_name);
 
-        void version();
+        Result<void> version();
 
         Vector<PositionalArgument> m_positional_args;
         Vector<SwitchArgument> m_switch_args;
@@ -203,5 +214,6 @@ namespace os
         bool m_add_long_help_flag { false };
         bool m_add_short_version_flag { false };
         bool m_add_long_version_flag { false };
+        bool m_should_exit_on_bad_usage { true };
     };
 }

libos/src/ArgumentParser.cpp

@@ -126,7 +126,7 @@ namespace os
         return arg.length() > 2 && arg[0] == '-' && arg[1] == '-';
     }
 
-    Result<void> ArgumentParser::parse(int argc, char* const* argv)
+    Result<bool> ArgumentParser::parse(int argc, char* const* argv)
     {
         StringView program_name = argv[0];
 
@@ -163,8 +163,17 @@ namespace os
 
                     bool found = false;
 
-                    if (m_add_long_help_flag && flag == "help"_sv) { TRY(usage(program_name)); }
-                    if (m_add_long_version_flag && flag == "version"_sv) { version(); }
+                    if (m_add_long_help_flag && flag == "help"_sv)
+                    {
+                        TRY(usage(program_name));
+                        return false;
+                    }
+
+                    if (m_add_long_version_flag && flag == "version"_sv)
+                    {
+                        version();
+                        return false;
+                    }
 
                     for (const auto& current : m_switch_args)
                     {
@@ -196,6 +205,7 @@ namespace os
 
                     os::eprintln("%s: unrecognized option '%s'", program_name.chars(), arg.chars());
                     short_usage(program_name);
+                    return false;
                 }
                 else if (looks_like_short_flag(arg))
                 {
@@ -206,8 +216,17 @@ namespace os
                         char c = flags[j];
                         bool found = false;
 
-                        if (m_add_short_help_flag && c == 'h') { TRY(usage(program_name)); }
-                        if (m_add_short_version_flag && c == 'v') { version(); }
+                        if (m_add_short_help_flag && c == 'h')
+                        {
+                            TRY(usage(program_name));
+                            return false;
+                        }
+
+                        if (m_add_short_version_flag && c == 'v')
+                        {
+                            version();
+                            return false;
+                        }
 
                         // Last flag, this could be a value flag
                         if (j + 1 == flags.length())
@@ -244,6 +263,7 @@ namespace os
 
                         os::eprintln("%s: invalid option -- '%c'", program_name.chars(), c);
                         short_usage(program_name);
+                        return false;
                     }
 
                     continue;
@@ -276,6 +296,7 @@ namespace os
             os::eprintln("%s: option '-%c' requires an argument", program_name.chars(),
                          current_value_argument->short_flag);
             short_usage(program_name);
+            return false;
         }
 
         if (is_parsing_argument_vector)
@@ -292,6 +313,7 @@ namespace os
                     {
                         os::eprintln("%s: required argument '%s' not provided", program_name.chars(), arg.name.chars());
                         short_usage(program_name);
+                        return false;
                     }
                     else { *arg.out = arg.fallback; }
                 }
@@ -308,6 +330,7 @@ namespace os
                 {
                     os::eprintln("%s: required argument '%s' not provided", program_name.chars(), arg.name.chars());
                     short_usage(program_name);
+                    return false;
                 }
                 else
                 {
@@ -321,7 +344,7 @@ namespace os
             }
         }
 
-        return {};
+        return true;
     }
 
     Result<void> ArgumentParser::usage(StringView program_name)
@@ -400,10 +423,12 @@ namespace os
         else
             printf("  -%-25c %s\n", 'v', "show version information and exit");
 
-        exit(0);
+        if (m_should_exit_on_bad_usage) exit(0);
+        else
+            return {};
     }
 
-    void ArgumentParser::version()
+    Result<void> ArgumentParser::version()
     {
         if (m_program_info.package.is_empty())
             printf("%s %s\n", m_program_info.name.chars(), m_program_info.version.chars());
@@ -415,15 +440,19 @@ namespace os
 
         if (!m_program_info.authors.is_empty()) printf("\n%s\n", m_program_info.authors.chars());
 
-        exit(0);
+        if (m_should_exit_on_bad_usage) exit(0);
+        else
+            return {};
     }
 
-    void ArgumentParser::short_usage(StringView program_name)
+    Result<void> ArgumentParser::short_usage(StringView program_name)
     {
         if (m_add_short_help_flag || m_add_long_help_flag)
             os::eprintln("Try running '%s %s' for more information.", program_name.chars(),
                          m_add_long_help_flag ? "--help" : "-h");
 
-        exit(1);
+        if (m_should_exit_on_bad_usage) exit(1);
+        else
+            return {};
     }
 }

shell/CMakeLists.txt

@@ -0,0 +1,12 @@
+set(SOURCES
+    main.cpp
+    sh.h
+    builtin/cd.cpp
+)
+
+add_executable(sh ${SOURCES})
+target_compile_options(sh PRIVATE -Os ${COMMON_FLAGS} -Wno-write-strings)
+add_dependencies(sh libc)
+target_include_directories(sh PRIVATE ${LUNA_BASE}/usr/include ${CMAKE_CURRENT_LIST_DIR})
+target_link_libraries(sh PRIVATE os)
+install(TARGETS sh DESTINATION ${LUNA_BASE}/usr/bin)

shell/builtin/cd.cpp

@@ -0,0 +1,24 @@
+#include "sh.h"
+#include <luna/String.h>
+#include <os/ArgumentParser.h>
+#include <os/FileSystem.h>
+
+shell_builtin_t builtin_cd = [](int argc, char** argv) -> Result<void> {
+    StringView directory;
+
+    os::ArgumentParser parser;
+    parser.set_should_exit_on_bad_usage(false);
+    parser.add_description("Change working directory (shell builtin)"_sv);
+    parser.add_system_program_info("cd"_sv);
+    parser.add_positional_argument(directory, "directory"_sv, false);
+    if (!TRY(parser.parse(argc, argv))) return {};
+
+    if (!directory.is_empty()) TRY(os::FileSystem::change_directory(directory));
+    else
+    {
+        auto home = TRY(os::FileSystem::home_directory());
+        TRY(os::FileSystem::change_directory(home.view()));
+    }
+
+    return {};
+};

shell/main.cpp

@@ -1,3 +1,4 @@
+#include "sh.h"
 #include <errno.h>
 #include <luna/String.h>
 #include <luna/Vector.h>
@@ -15,6 +16,12 @@
 #include <termios.h>
 #include <unistd.h>
 
+#include <luna/HashMap.h>
+
+extern shell_builtin_t builtin_cd;
+
+static HashMap<StringView, shell_builtin_t> s_builtins;
+
 using os::File;
 
 static Result<Vector<String>> split_command_into_args(StringView cmd)
@@ -32,6 +39,15 @@ static Result<void> execute_command(StringView command)
     return os::Process::exec(args[0].view(), args.slice());
 }
 
+static Result<void> init_builtins()
+{
+    s_builtins = {};
+
+    TRY(s_builtins.try_set("cd"_sv, builtin_cd));
+
+    return {};
+}
+
 // Do nothing, but we need a handler so read() returns EINTR.
 static void sigint_handler(int)
 {
@@ -87,6 +103,8 @@ Result<int> luna_main(int argc, char** argv)
         tcsetpgrp(STDIN_FILENO, getpgid(0));
     }
 
+    init_builtins();
+
     while (1)
     {
         if (interactive)
@@ -117,20 +135,30 @@ Result<int> luna_main(int argc, char** argv)
 
         if (strcspn(cmd.chars(), " #") == 0) continue;
 
-        if (!strncmp(cmd.chars(), "cd", 2))
-        {
-            auto args = TRY(split_command_into_args(cmd.view()));
-            check(args[0].view() == "cd");
+        auto args = TRY(split_command_into_args(cmd.view()));
+        if (args.size() < 1) continue;
 
-            if (args.size() == 1)
+        if (!strchr(args[0].chars(), '/'))
+        {
+            auto maybe_builtin = s_builtins.try_get(args[0].view());
+
+            if (maybe_builtin.has_value())
             {
-                auto home = TRY(os::FileSystem::home_directory());
-                TRY(os::FileSystem::change_directory(home.view()));
+                auto builtin = maybe_builtin.value();
+
+                Vector<const char*> argv;
+                for (const auto& arg : args) { TRY(argv.try_append(arg.chars())); }
+                TRY(argv.try_append(nullptr));
+
+                auto rc = builtin((int)args.size(), const_cast<char**>(argv.data()));
+                if (rc.has_error())
+                {
+                    errno = rc.error();
+                    perror(argv[0]);
+                }
+
                 continue;
             }
-
-            TRY(os::FileSystem::change_directory(args[1].view()));
-            continue;
         }
 
         pid_t child = TRY(os::Process::fork());
@@ -140,15 +168,15 @@ Result<int> luna_main(int argc, char** argv)
             if (interactive)
             {
                 setpgid(0, 0);
-                tcsetpgrp(STDIN_FILENO, getpid());
+                tcsetpgrp(input_file->fd(), getpid());
             }
-            TRY(execute_command(cmd.view()));
+            TRY(os::Process::exec(args[0].view(), args.slice()));
         }
 
         int status;
         TRY(os::Process::wait(child, &status));
 
-        if (interactive) tcsetpgrp(STDIN_FILENO, getpgid(0));
+        if (interactive) tcsetpgrp(input_file->fd(), getpgid(0));
 
         if (WIFSIGNALED(status))
         {

shell/sh.h

@@ -0,0 +1,4 @@
+#pragma once
+#include <luna/Result.h>
+
+typedef Result<void> (*shell_builtin_t)(int, char**);