diff --git a/ChangeLog b/ChangeLog
index 163f4047eb..09681d5c1a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Feb  8 23:22:35 2009  Tanaka Akira  <akr@fsij.org>
+
+	* ext/socket/option.c (inspect_peercred): new function to show
+	  SO_PEERCRED socket option.
+
 Sun Feb  8 22:44:20 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* include/ruby/backward/rubysig.h (rb_thread_blocking_region_begin),
diff --git a/ext/socket/option.c b/ext/socket/option.c
index 8fcee4c0c7..283dd7b279 100644
--- a/ext/socket/option.c
+++ b/ext/socket/option.c
@@ -221,6 +221,23 @@ inspect_timeval(int level, int optname, VALUE data, VALUE ret)
     }
 }
 
+#if defined(SOL_SOCKET) && defined(SO_PEERCRED) /* GNU/Linux */
+static int
+inspect_peercred(int level, int optname, VALUE data, VALUE ret)
+{
+    if (RSTRING_LEN(data) == sizeof(struct ucred)) {
+        struct ucred cred;
+        memcpy(&cred, RSTRING_PTR(data), sizeof(struct ucred));
+        rb_str_catf(ret, " pid=%u uid=%u gid=%u", cred.pid, cred.uid, cred.gid);
+        rb_str_cat2(ret, " (ucred)");
+        return 0;
+    }
+    else {
+        return -1;
+    }
+}
+#endif
+
 static VALUE
 sockopt_inspect(VALUE self)
 {
@@ -299,6 +316,9 @@ sockopt_inspect(VALUE self)
 #        if defined(SO_SNDTIMEO) /* POSIX */
           case SO_SNDTIMEO: if (inspect_timeval(level, optname, data, ret) == -1) goto dump; break;
 #        endif
+#        if defined(SO_PEERCRED) /* GNU/Linux */
+          case SO_PEERCRED: if (inspect_peercred(level, optname, data, ret) == -1) goto dump; break;
+#        endif
 
           default: goto dump;
         }
diff --git a/test/socket/test_unix.rb b/test/socket/test_unix.rb
index 31d60e3ff3..ca4b17b3f4 100644
--- a/test/socket/test_unix.rb
+++ b/test/socket/test_unix.rb
@@ -296,7 +296,23 @@ class TestUNIXSocket < Test::Unit::TestCase
     }
   end
 
-  def test_cred_ucred
+  def test_getcred_ucred
+    return if /linux/ !~ RUBY_PLATFORM
+    Dir.mktmpdir {|d|
+      sockpath = "#{d}/sock"
+      serv = Socket.unix_server_socket(sockpath)
+      c = Socket.unix(sockpath)
+      s, = serv.accept
+      cred = s.getsockopt(:SOCKET, :PEERCRED)
+      inspect = cred.inspect
+      assert_match(/ pid=#{$$} /, inspect)
+      assert_match(/ uid=#{Process.uid} /, inspect)
+      assert_match(/ gid=#{Process.gid} /, inspect)
+      assert_match(/ \(ucred\)/, inspect)
+    }
+  end
+
+  def test_sendcred_ucred
     return if /linux/ !~ RUBY_PLATFORM
     Dir.mktmpdir {|d|
       sockpath = "#{d}/sock"
@@ -310,12 +326,12 @@ class TestUNIXSocket < Test::Unit::TestCase
       assert_equal("a", msg)
       assert_match(/ pid=#{$$} /, inspect)
       assert_match(/ uid=#{Process.uid} /, inspect)
-      assert_match(/ gid=#{Process.gid}>/, inspect)
+      assert_match(/ gid=#{Process.gid} /, inspect)
       assert_match(/ \(ucred\)/, inspect)
     }
   end
 
-  def test_cred_sockcred
+  def test_sendcred_sockcred
     return if /netbsd|freebsd/ !~ RUBY_PLATFORM
     Dir.mktmpdir {|d|
       sockpath = "#{d}/sock"
@@ -336,7 +352,7 @@ class TestUNIXSocket < Test::Unit::TestCase
     }
   end
 
-  def test_cred_cmsgcred
+  def test_sendcred_cmsgcred
     return if /freebsd/ !~ RUBY_PLATFORM
     Dir.mktmpdir {|d|
       sockpath = "#{d}/sock"