diff --git a/ChangeLog b/ChangeLog
index c90b21e2ee8208..4e8fa65845b690 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Oct  9 17:13:27 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* process.c (rb_execarg_addopt, rb_execarg_run_options): add :uid and
+	  :gid options.  [ruby-core:47414] [Feature #6975]
+
 Tue Oct  9 14:36:11 2012  Koichi Sasada  <ko1@atdot.net>
 
 	* iseq.c (iseq_free): fix memory leak.
diff --git a/internal.h b/internal.h
index 3a2331a867ae10..e538de4404f91d 100644
--- a/internal.h
+++ b/internal.h
@@ -203,9 +203,13 @@ struct rb_execarg {
     unsigned chdir_given : 1;
     unsigned new_pgroup_given : 1;
     unsigned new_pgroup_flag : 1;
+    unsigned uid_given : 1;
+    unsigned gid_given : 1;
     rb_pid_t pgroup_pgid; /* asis(-1), new pgroup(0), specified pgroup (0<V). */
     VALUE rlimit_limits; /* Qfalse or [[rtype, softlim, hardlim], ...] */
     mode_t umask_mask;
+    rb_uid_t uid;
+    rb_gid_t gid;
     VALUE fd_dup2;
     VALUE fd_close;
     VALUE fd_open;
diff --git a/process.c b/process.c
index 270ee769c91283..bd3cea94eac8de 100644
--- a/process.c
+++ b/process.c
@@ -136,6 +136,55 @@ int setregid(rb_gid_t rgid, rb_gid_t egid);
 #define preserving_errno(stmts) \
 	do {int saved_errno = errno; stmts; errno = saved_errno;} while (0)
 
+static void check_uid_switch(void);
+static void check_gid_switch(void);
+
+#if 1
+#define p_uid_from_name p_uid_from_name
+#define p_gid_from_name p_gid_from_name
+#endif
+
+#if defined(HAVE_PWD_H)
+# ifdef HAVE_GETPWNAM_R
+#   define PREPARE_GETPWNAM \
+    long getpw_buf_len = sysconf(_SC_GETPW_R_SIZE_MAX); \
+    char *getpw_buf = ALLOCA_N(char, (getpw_buf_len < 0 ? (getpw_buf_len = 4096) : getpw_buf_len));
+#   define OBJ2UID(id) obj2uid((id), getpw_buf, getpw_buf_len)
+static rb_uid_t obj2uid(VALUE id, char *getpw_buf, size_t getpw_buf_len);
+# else
+#   define PREPARE_GETPWNAM	/* do nothing */
+#   define OBJ2UID(id) obj2uid((id))
+static rb_uid_t obj2uid(VALUE id);
+# endif
+#else
+# define PREPARE_GETPWNAM	/* do nothing */
+# define OBJ2UID(id) NUM2UIDT(id)
+# ifdef p_uid_from_name
+#   undef p_uid_from_name
+#   define p_uid_from_name rb_f_notimplement
+# endif
+#endif
+
+#if defined(HAVE_GRP_H)
+# ifdef HAVE_GETGRNAM_R
+#   define PREPARE_GETGRNAM \
+    long getgr_buf_len = sysconf(_SC_GETGR_R_SIZE_MAX); \
+    char *getgr_buf = ALLOCA_N(char, (getgr_buf_len < 0 ? (getgr_buf_len = 4096) : getgr_buf_len));
+#   define OBJ2GID(id) obj2gid((id), getgr_buf, getgr_buf_len)
+static rb_gid_t obj2gid(VALUE id, char *getgr_buf, size_t getgr_buf_len);
+# else
+#   define PREPARE_GETGRNAM	/* do nothing */
+#   define OBJ2GID(id) obj2gid((id))
+static rb_gid_t obj2gid(VALUE id);
+# endif
+#else
+# define PREPARE_GETGRNAM	/* do nothing */
+# define OBJ2GID(id) NUM2GIDT(id)
+# ifdef p_gid_from_name
+#   undef p_gid_from_name
+#   define p_gid_from_name rb_f_notimplement
+# endif
+#endif
 
 /*
  *  call-seq:
@@ -1664,6 +1713,38 @@ rb_execarg_addopt(VALUE execarg_obj, VALUE key, VALUE val)
             key = INT2FIX(2);
             goto redirect;
         }
+	else if (id == rb_intern("uid")) {
+#ifdef HAVE_SETUID
+	    if (eargp->uid_given) {
+		rb_raise(rb_eArgError, "uid option specified twice");
+	    }
+	    check_uid_switch();
+	    {
+		PREPARE_GETPWNAM;
+		eargp->uid = OBJ2UID(val);
+		eargp->uid_given = 1;
+	    }
+#else
+	    rb_raise(rb_eNotImpError,
+		     "uid option is unimplemented on this machine");
+#endif
+	}
+	else if (id == rb_intern("gid")) {
+#ifdef HAVE_SETGID
+	    if (eargp->gid_given) {
+		rb_raise(rb_eArgError, "gid option specified twice");
+	    }
+	    check_gid_switch();
+	    {
+		PREPARE_GETGRNAM;
+		eargp->gid = OBJ2GID(val);
+		eargp->gid_given = 1;
+	    }
+#else
+	    rb_raise(rb_eNotImpError,
+		     "gid option is unimplemented on this machine");
+#endif
+	}
         else {
 	    return ST_STOP;
         }
@@ -2875,6 +2956,23 @@ rb_execarg_run_options(const struct rb_execarg *eargp, struct rb_execarg *sargp,
         }
     }
 
+#ifdef HAVE_SETGID
+    if (eargp->gid_given) {
+	if (setgid(eargp->gid) < 0) {
+	    ERRMSG("setgid");
+	    return -1;
+	}
+    }
+#endif
+#ifdef HAVE_SETUID
+    if (eargp->uid_given) {
+	if (setuid(eargp->uid) < 0) {
+	    ERRMSG("setuid");
+	    return -1;
+	}
+    }
+#endif
+
     if (sargp) {
         VALUE ary = sargp->fd_dup2;
         if (ary != Qfalse) {
@@ -4581,22 +4679,7 @@ check_gid_switch(void)
  *  <code>Process::UID</code>, and <code>Process::GID</code> modules.
  */
 
-#if 1
-#define p_uid_from_name p_uid_from_name
-#define p_gid_from_name p_gid_from_name
-#endif
-
 #if defined(HAVE_PWD_H)
-# ifdef HAVE_GETPWNAM_R
-#   define PREPARE_GETPWNAM \
-    long getpw_buf_len = sysconf(_SC_GETPW_R_SIZE_MAX); \
-    char *getpw_buf = ALLOCA_N(char, (getpw_buf_len < 0 ? (getpw_buf_len = 4096) : getpw_buf_len));
-#   define OBJ2UID(id) obj2uid((id), getpw_buf, getpw_buf_len)
-# else
-#   define PREPARE_GETPWNAM	/* do nothing */
-#   define OBJ2UID(id) obj2uid((id))
-# endif
-
 static rb_uid_t
 obj2uid(VALUE id
 # ifdef HAVE_GETPWNAM_R
@@ -4642,26 +4725,9 @@ p_uid_from_name(VALUE self, VALUE id)
     return UIDT2NUM(OBJ2UID(id));
 }
 # endif
-#else
-# define PREPARE_GETPWNAM	/* do nothing */
-# define OBJ2UID(id) NUM2UIDT(id)
-# ifdef p_uid_from_name
-#   undef p_uid_from_name
-#   define p_uid_from_name rb_f_notimplement
-# endif
 #endif
 
 #if defined(HAVE_GRP_H)
-# ifdef HAVE_GETGRNAM_R
-#   define PREPARE_GETGRNAM \
-    long getgr_buf_len = sysconf(_SC_GETGR_R_SIZE_MAX); \
-    char *getgr_buf = ALLOCA_N(char, (getgr_buf_len < 0 ? (getgr_buf_len = 4096) : getgr_buf_len));
-#   define OBJ2GID(id) obj2gid((id), getgr_buf, getgr_buf_len)
-# else
-#   define PREPARE_GETGRNAM	/* do nothing */
-#   define OBJ2GID(id) obj2gid((id))
-# endif
-
 static rb_gid_t
 obj2gid(VALUE id
 # ifdef HAVE_GETGRNAM_R
@@ -4707,13 +4773,6 @@ p_gid_from_name(VALUE self, VALUE id)
     return GIDT2NUM(OBJ2GID(id));
 }
 # endif
-#else
-# define PREPARE_GETGRNAM	/* do nothing */
-# define OBJ2GID(id) NUM2GIDT(id)
-# ifdef p_gid_from_name
-#   undef p_gid_from_name
-#   define p_gid_from_name rb_f_notimplement
-# endif
 #endif
 
 #if defined HAVE_SETUID
diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index 134797c2ad018f..e8c4cfa7d9344b 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -1478,6 +1478,50 @@ def test_execopts_new_pgroup
     assert_nothing_raised { IO.popen([*TRUECOMMAND, :new_pgroup=>true]) {} }
   end
 
+  def test_execopts_uid
+    feature6975 = '[ruby-core:47414]'
+
+    [30000, [ENV["USER"], Process.uid]].each do |user, uid|
+      assert_nothing_raised(feature6975) do
+        begin
+          system(*TRUECOMMAND, uid: user)
+        rescue Errno::EPERM, NotImplementedError
+        end
+      end
+
+      uid = "#{uid || user}"
+      assert_nothing_raised(feature6975) do
+        begin
+          u = IO.popen([RUBY, "-e", "print Process.uid", uid: user], &:read)
+          assert_equal(uid, u, feature6975)
+        rescue Errno::EPERM, NotImplementedError
+        end
+      end
+    end
+  end
+
+  def test_execopts_gid
+    feature6975 = '[ruby-core:47414]'
+
+    [30000, *Process.groups.map {|g| g = Etc.getgrgid(g); [g.name, g.gid]}].each do |group, gid|
+      assert_nothing_raised(feature6975) do
+        begin
+          system(*TRUECOMMAND, gid: group)
+        rescue Errno::EPERM, NotImplementedError
+        end
+      end
+
+      gid = "#{gid || group}"
+      assert_nothing_raised(feature6975) do
+        begin
+          g = IO.popen([RUBY, "-e", "print Process.gid", gid: group], &:read)
+          assert_equal(gid, g, feature6975)
+        rescue Errno::EPERM, NotImplementedError
+        end
+      end
+    end
+  end
+
   def test_sigpipe
     system(RUBY, "-e", "")
     with_pipe {|r, w|