diff --git a/pkgs/mruby/src/cmdline.c b/pkgs/mruby/src/cmdline.c
new file mode 100644
index 0000000..be2977e
--- /dev/null
+++ b/pkgs/mruby/src/cmdline.c
@@ -0,0 +1,71 @@
+#include "main.h"
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+#include <kernaux.h>
+
+#include <mruby.h>
+#include <mruby/array.h>
+#include <mruby/presym.h>
+#include <mruby/string.h>
+
+#define ARGV_COUNT_MAX 256
+#define BUFFER_SIZE 4096
+
+static mrb_value rb_KernAux_cmdline(mrb_state *mrb, mrb_value self);
+
+void init_cmdline(mrb_state *const mrb)
+{
+    struct RClass *const rb_KernAux = mrb_module_get_id(mrb, MRB_SYM(KernAux));
+    struct RClass *const rb_KernAux_Error =
+        mrb_class_get_under_id(mrb, rb_KernAux, MRB_SYM(Error));
+
+    mrb_define_class_under_id(mrb, rb_KernAux, MRB_SYM(CmdlineError),
+                              rb_KernAux_Error);
+
+    mrb_define_class_method(mrb, rb_KernAux, "cmdline",
+                            rb_KernAux_cmdline, MRB_ARGS_REQ(1));
+}
+
+mrb_value rb_KernAux_cmdline(mrb_state *const mrb, mrb_value self)
+{
+    const char *str;
+    mrb_get_args(mrb, "z", &str);
+    size_t argc;
+    char error_msg[KERNAUX_CMDLINE_ERROR_MSG_SIZE_MAX];
+    char **const argv = malloc(sizeof(char*) * ARGV_COUNT_MAX);
+    char *const buffer = malloc(BUFFER_SIZE);
+
+    const bool status = kernaux_cmdline(
+        str,
+        error_msg,
+        &argc,
+        argv,
+        buffer,
+        ARGV_COUNT_MAX,
+        BUFFER_SIZE
+    );
+
+    if (!status) {
+        free(argv);
+        free(buffer);
+        struct RClass *const rb_KernAux =
+            mrb_module_get_id(mrb, MRB_SYM(KernAux));
+        struct RClass *const rb_KernAux_CmdlineError =
+            mrb_class_get_under_id(mrb, rb_KernAux, MRB_SYM(CmdlineError));
+        mrb_raise(mrb, rb_KernAux_CmdlineError, error_msg);
+    }
+
+    mrb_value values[argc];
+    for (size_t index = 0; index < argc; ++index) {
+        values[index] = mrb_obj_freeze(
+            mrb,
+            mrb_str_cat_cstr(mrb, mrb_str_new_lit(mrb, ""), argv[index])
+        );
+    }
+    free(argv);
+    free(buffer);
+    return mrb_obj_freeze(mrb, mrb_ary_new_from_values(mrb, argc, values));
+}
diff --git a/pkgs/mruby/src/main.c b/pkgs/mruby/src/main.c
index 7aeb06a..5bfb8e9 100644
--- a/pkgs/mruby/src/main.c
+++ b/pkgs/mruby/src/main.c
@@ -26,6 +26,7 @@ void mrb_mruby_kernaux_gem_init(mrb_state *const mrb)
 
     init_assert(mrb);
     init_ntoa(mrb);
+    init_cmdline(mrb);
 }
 
 void current_mrb_start(mrb_state *mrb)
diff --git a/pkgs/mruby/src/main.h b/pkgs/mruby/src/main.h
index 1eb543f..25ee917 100644
--- a/pkgs/mruby/src/main.h
+++ b/pkgs/mruby/src/main.h
@@ -9,5 +9,6 @@ mrb_state *current_mrb_get();
 
 void init_assert(mrb_state *mrb);
 void init_ntoa(mrb_state *mrb);
+void init_cmdline(mrb_state *mrb);
 
 #endif
diff --git a/pkgs/mruby/test/cmdline.rb b/pkgs/mruby/test/cmdline.rb
new file mode 100644
index 0000000..60f6560
--- /dev/null
+++ b/pkgs/mruby/test/cmdline.rb
@@ -0,0 +1,70 @@
+def test_cmdline(str, expected)
+  result = KernAux.cmdline str
+
+  assert_true result.instance_of? Array
+  assert_true result.frozen?
+  result.each do |item|
+    assert_true item.instance_of? String
+    assert_true item.frozen?
+  end
+
+  assert_equal result, expected
+end
+
+assert 'default' do
+  test_cmdline 'foo bar\\ baz "car cdr"', ['foo', 'bar baz', 'car cdr']
+end
+
+assert 'when str is empty' do
+  test_cmdline '', []
+end
+
+assert 'when str has invalid type' do
+  assert_raise TypeError, 'Integer cannot be converted to String' do
+    KernAux.cmdline 123
+  end
+end
+
+assert 'when str has EOL after backslash' do
+  assert_raise KernAux::CmdlineError, 'EOL after backslash' do
+    KernAux.cmdline '\\'
+  end
+end
+
+assert 'when str has EOL after backslash inside quote' do
+  assert_raise KernAux::CmdlineError, 'EOL after backslash inside quote' do
+    KernAux.cmdline '"\\'
+  end
+end
+
+assert 'when str has unescaped quotation mark' do
+  assert_raise KernAux::CmdlineError, 'unescaped quotation mark' do
+    KernAux.cmdline 'foo"'
+  end
+end
+
+assert 'when str has EOL inside quote' do
+  assert_raise KernAux::CmdlineError, 'EOL inside quote' do
+    KernAux.cmdline '"'
+  end
+end
+
+assert 'when there are not too many args' do
+  test_cmdline 'a ' * 256, ['a'] * 256
+end
+
+assert 'when there are too many args' do
+  assert_raise KernAux::CmdlineError, 'too many args' do
+    KernAux.cmdline 'a ' * 257
+  end
+end
+
+assert 'when args don\'t cause buffer overflow' do
+  test_cmdline 'a' * 4095, ['a' * 4095]
+end
+
+assert 'when args cause buffer overflow' do
+  assert_raise KernAux::CmdlineError, 'buffer overflow' do
+    KernAux.cmdline 'a' * 4096
+  end
+end