tools/lxc-attach: add -u and -g arguments

doc/lxc-attach.sgml.in

@@ -60,6 +60,8 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
       <arg choice="opt">--clear-env</arg>
       <arg choice="opt">-v, --set-var <replaceable>variable</replaceable></arg>
       <arg choice="opt">--keep-var <replaceable>variable</replaceable></arg>
+      <arg choice="opt">-u, --uid <replaceable>uid</replaceable></arg>
+      <arg choice="opt">-g, --gid <replaceable>gid</replaceable></arg>
       <arg choice="opt">-- <replaceable>command</replaceable></arg>
     </cmdsynopsis>
   </refsynopsisdiv>
@@ -282,6 +284,30 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 	</listitem>
       </varlistentry>
 
+      <varlistentry>
+	<term>
+	  <option>--u, --uid <replaceable>uid</replaceable></option>
+	</term>
+	<listitem>
+	  <para>
+	    Executes the <replaceable>command</replaceable> with user ID
+	   <replaceable>uid</replaceable> inside the container.
+	  </para>
+	</listitem>
+      </varlistentry>
+
+      <varlistentry>
+	<term>
+	  <option>--g, --gid <replaceable>gid</replaceable></option>
+	</term>
+	<listitem>
+	  <para>
+	    Executes the <replaceable>command</replaceable> with group ID
+	   <replaceable>gid</replaceable> inside the container.
+	  </para>
+	</listitem>
+      </varlistentry>
+
      </variablelist>
 
   </refsect1>

doc/lxc-execute.sgml.in

@@ -53,6 +53,8 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
       <arg choice="opt">-d</arg>
       <arg choice="opt">-f <replaceable>config_file</replaceable></arg>
       <arg choice="opt">-s KEY=VAL</arg>
+      <arg choice="opt">-u, --uid <replaceable>uid</replaceable></arg>
+      <arg choice="opt">-g, --gid <replaceable>gid</replaceable></arg>
       <arg choice="opt">-- <replaceable>command</replaceable></arg>
     </cmdsynopsis>
   </refsynopsisdiv>
@@ -140,6 +142,30 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
       </varlistentry>
 
       <varlistentry>
+	<term>
+	  <option>--u, --uid <replaceable>uid</replaceable></option>
+	</term>
+	<listitem>
+	  <para>
+	    Executes the <replaceable>command</replaceable> with user ID
+	   <replaceable>uid</replaceable> inside the container.
+	  </para>
+	</listitem>
+      </varlistentry>
+
+      <varlistentry>
+	<term>
+	  <option>--g, --gid <replaceable>gid</replaceable></option>
+	</term>
+	<listitem>
+	  <para>
+	    Executes the <replaceable>command</replaceable> with group ID
+	   <replaceable>gid</replaceable> inside the container.
+	  </para>
+	</listitem>
+      </varlistentry>
+
+      <varlistentry>
 	<term><option>--</option></term>
 	<listitem>
 	  <para>

src/lxc/tools/lxc_attach.c

@@ -72,6 +72,8 @@ static const struct option my_longopts[] = {
 	{"set-var", required_argument, 0, 'v'},
 	{"pty-log", required_argument, 0, 'L'},
 	{"rcfile", required_argument, 0, 'f'},
+	{"uid", required_argument, 0, 'u'},
+	{"gid", required_argument, 0, 'g'},
 	LXC_COMMON_OPTIONS
 };
 
@@ -122,6 +124,8 @@ Options :\n\
                     multiple times.\n\
   -f, --rcfile=FILE\n\
                     Load configuration file FILE\n\
+  -u, --uid=UID     Execute COMMAND with UID inside the container\n\
+  -g, --gid=GID     Execute COMMAND with GID inside the container\n\
 ",
 	.options      = my_longopts,
 	.parser       = my_parser,
@@ -187,6 +191,14 @@ static int my_parser(struct lxc_arguments *args, int c, char *arg)
 	case 'f':
 		args->rcfile = arg;
 		break;
+	case 'u':
+		if (lxc_safe_uint(arg, &args->uid) < 0)
+			return -1;
+		break;
+	case 'g':
+		if (lxc_safe_uint(arg, &args->gid) < 0)
+			return -1;
+		break;
 	}
 
 	return 0;
@@ -333,6 +345,12 @@ int main(int argc, char *argv[])
 			goto out;
 	}
 
+	if (my_args.uid)
+		attach_options.uid = my_args.uid;
+
+	if (my_args.gid)
+		attach_options.gid = my_args.gid;
+
 	if (command.program)
 		ret = c->attach(c, lxc_attach_run_command, &command, &attach_options, &pid);
 	else