tools/kvm_stat: print error on invalid regex

BugLink: http://bugs.launchpad.net/bugs/1734130
Entering an invalid regular expression did not produce any indication of an
error so far.
To reproduce, press 'f' and enter 'foo(' (with an unescaped bracket).

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 1cd8bfb1ed9962be6d80d5020508922aa93653ac)
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/tools/kvm/kvm_stat/kvm_stat b/tools/kvm/kvm_stat/kvm_stat
index 4e0f282c52896489fcdb5d25974d07a80ec7531e..08f842238c3207b8ee5aa830e47b7eefe93652d5 100755 (executable)
--- a/tools/kvm/kvm_stat/kvm_stat
+++ b/tools/kvm/kvm_stat/kvm_stat
@@ -1176,6 +1176,7 @@ class Tui(object):
         Asks for a valid regex and sets the fields filter accordingly.
 
         """
+        msg = ''
         while True:
             self.screen.erase()
             self.screen.addstr(0, 0,
@@ -1184,6 +1185,7 @@ class Tui(object):
             self.screen.addstr(2, 0,
                                "Current regex: {0}"
                                .format(self.stats.fields_filter))
+            self.screen.addstr(5, 0, msg)
             self.screen.addstr(3, 0, "New regex: ")
             curses.echo()
             regex = self.screen.getstr().decode(ENCODING)
@@ -1198,6 +1200,7 @@ class Tui(object):
                 self.refresh_header()
                 return
             except re.error:
+                msg = '"' + regex + '": Not a valid regular expression'
                 continue
 
     def show_vm_selection_by_pid(self):