diff --git a/perl-xCAT/xCAT/DBobjUtils.pm b/perl-xCAT/xCAT/DBobjUtils.pm
index 67f4fa4a5..d3a23cfcc 100644
--- a/perl-xCAT/xCAT/DBobjUtils.pm
+++ b/perl-xCAT/xCAT/DBobjUtils.pm
@@ -1592,9 +1592,8 @@ sub getGroupMembers
         {
             my $rsp;
             $rsp->{data}->[0] =
-              "The \'-w\' option has an incorrect attr=val pair.";
+              "The \'-w\' option has an incorrect attr*val pair.";
             xCAT::MsgUtils->message("E", $rsp, $::callback);
-            next;
         }
 
         # see what nodes have these attr=values
diff --git a/perl-xCAT/xCAT/Utils.pm b/perl-xCAT/xCAT/Utils.pm
index a81dbdecf..f5a021c1d 100644
--- a/perl-xCAT/xCAT/Utils.pm
+++ b/perl-xCAT/xCAT/Utils.pm
@@ -4221,23 +4221,25 @@ sub parse_selection_string()
 {
     my ($class, $ss_ref, $wherehash_ref) = @_;
 
+    # selection string is specified with one or multiple -w flags
+    # stored in an array
     foreach my $m (@{$ss_ref})
     {
         my $attr;
         my $val;
         my $matchtype;
-        if ($m =~ /^[^=]*\==/) {
+        if ($m =~ /^[^=]*\==/) { #attr==val
             ($attr, $val) = split /==/,$m,2;
             $matchtype='match';
-        } elsif ($m =~ /^[^=]*=~/) {
+        } elsif ($m =~ /^[^=]*=~/) { #attr=~val
             ($attr, $val) = split /=~/,$m,2;
             $val =~ s/^\///;
             $val =~ s/\/$//;
             $matchtype='regex';
-        } elsif ($m =~ /^[^=]*\!=/) {
+        } elsif ($m =~ /^[^=]*\!=/) { #attr!=val
              ($attr,$val) = split /!=/,$m,2;
              $matchtype='natch';
-        } elsif ($m =~ /[^=]*!~/) {
+        } elsif ($m =~ /[^=]*!~/) { #attr!~val
             ($attr,$val) = split /!~/,$m,2;
             $val =~ s/^\///;
             $val =~ s/\/$//;
@@ -4300,7 +4302,7 @@ sub selection_string_match()
                      last;
                  }
              }
-             if(($wherehash{$testattr}{'matchtype'} eq 'natch')) { #attr!=val
+             if($wherehash{$testattr}{'matchtype'} eq 'natch') { #attr!=val
                  if ($objhash_ref->{$objname}->{$testattr} eq $wherehash{$testattr}{'val'}) {
                      $match = 0;
                      last;
diff --git a/xCAT-server/lib/xcat/plugins/DBobjectdefs.pm b/xCAT-server/lib/xcat/plugins/DBobjectdefs.pm
index f5e658be1..3d068e316 100644
--- a/xCAT-server/lib/xcat/plugins/DBobjectdefs.pm
+++ b/xCAT-server/lib/xcat/plugins/DBobjectdefs.pm
@@ -1584,7 +1584,7 @@ sub defch
                     if ($rc != 0)
                     {
                          my $rsp;
-                         $rsp->{data}->[0] = "Incorrect selection string specified with -m flag";
+                         $rsp->{data}->[0] = "Incorrect selection string";
                          xCAT::MsgUtils->message("E", $rsp, $::callback);
                          return 3;
                     }
@@ -2938,7 +2938,7 @@ sub defmk_usage
     $rsp->{data}->[2] =
       "  mkdef [-V | --verbose] [-t object-types] [-o object-names] [-z|--stanza ]";
     $rsp->{data}->[3] =
-      "      [-d | --dynamic] [-w \"attr==val\" [-w \"attr=~val\"] ...]";
+      "      [-d | --dynamic] [-w attr==val [-w attr=~val] ...]";
     $rsp->{data}->[4] =
       "      [-f | --force] [noderange] [attr=val [attr=val...]]\n";
     $rsp->{data}->[5] =
@@ -2987,7 +2987,7 @@ sub defch_usage
     $rsp->{data}->[3] =
       "    [-z | --stanza] [-m | --minus] [-p | --plus]";
     $rsp->{data}->[4] =
-      "    [-w \"attr==val\" [-w \"attr=~val\"] ... ] [noderange] [attr=val [attr=val...]]\n";
+      "    [-w attr==val [-w attr=~val] ... ] [noderange] [attr=val [attr=val...]]\n";
     $rsp->{data}->[5] =
       "\nThe following data object types are supported by xCAT.\n";
     my $n = 6;
@@ -3033,7 +3033,7 @@ sub defls_usage
     $rsp->{data}->[3] =
       "    [ -l | --long] [-a | --all] [-z | --stanza ]";
     $rsp->{data}->[4] =
-      "    [-i attr-list] [-w \"attr==val\" [-w \"attr=~val\"] ...] [noderange]\n";
+      "    [-i attr-list] [-w attr==val [-w attr=~val] ...] [noderange]\n";
     $rsp->{data}->[5] =
       "\nThe following data object types are supported by xCAT.\n";
     my $n = 6;