Linux

Fixed Issue with "Open in External Browser" Option

Pull Request #145: "Incorrect method triggered for 'Launch External'" by mozbugbox fixes an often reported issue with launching links in external browser. Due to a copy an paste mistake the same callback was called for link menu options 'Open in External Browser' and 'Open in Browser'.

A screenshot of the menu options:

The difference between both option is that 'Open in External Browser' always launches the link in your favourite web browser while the other option does load links in Liferea if you specified so in the preferences. As 'Open in External Browser' incorrectly triggered the same callback as 'Open in Browser' the bug appeared depending on the preference settings.

Will be fixed with release 1.10.14 and 1.11.3

Static Code Analysis of any Autotools Project with OCLint

The following is a HowTo describing the setup of OCLint for any C/C++ project using autotools.

1. OCLint Setup

First step is downloading OCLint, as there are no package so far, it's just extracting the tarball somewhere in $HOME. Check out the latest release link on http://archives.oclint.org/releases/.

cd
wget "http://archives.oclint.org/releases/0.8/oclint-0.8.1-x86_64-linux-3.13.0-35-generic.tar.gz"
tar zxvf oclint-0.8.1-x86_64-linux-3.13.0-35-generic.tar.gz 

This should leave you with a copy of OCLint in ~/oclint-0.8.1

2. Bear Setup

As project usually consist of a lot of source files in different subdirectories it is hard for a linter to know where to look for files. While "cmake" has support for dumping a list of source files it processes during a run "make" doesn't. This is where the "Bear" wrapper comes to play: instead of

make

you run

bear make

so "bear" can track all files being compiled. It will dump a JSON file "compile_commands.json" which OCLint can use to do analysis of all files.

To setup Bear do the following

cd
git clone https://github.com/rizsotto/Bear.git
cd Bear
cmake .
make

3. Analyzing Code

Now we have all the tools we need. Let's download some autotools project like Liferea. Before doing code analysis it should be downloaded and build at least once:

git clone https://github.com/lwindolf/liferea.git
cd liferea
sh autogen.sh
make

Now we collect all code file compilation instructions with bear:

make clean
bear make

And if this succeed we can start a complete analysis with

~/oclint-0.8.1/bin/oclint-json-compilation-database

which will run OCLint with the input from "compile_commands.json" produced by "bear". Don't call "oclint" directly as you'd need to pass all compile flags manually.

If all went well you could see code analysis lines like those:

[...]
conf.c:263:9: useless parentheses P3 
conf.c:274:9: useless parentheses P3 
conf.c:284:9: useless parentheses P3 
conf.c:46:1: high cyclomatic complexity P2 Cyclomatic Complexity Number 33 exceeds limit of 10
conf.c:157:1: high cyclomatic complexity P2 Cyclomatic Complexity Number 12 exceeds limit of 10
conf.c:229:1: high cyclomatic complexity P2 Cyclomatic Complexity Number 30 exceeds limit of 10
conf.c:78:1: long method P3 Method with 55 lines exceeds limit of 50
conf.c:50:2: short variable name P3 Variable name with 2 characters is shorter than the threshold of 3
conf.c:52:2: short variable name P3 Variable name with 1 characters is shorter than the threshold of 3
[...]

Debugging dovecot ACL Shared Mailboxes Not Showing in Thunderbird

When you can't get ACL shared mailboxes visible with Dovecot and Thunderbird here are some debugging tipps:

  1. Thunderbird fetches the ACLs on startup (and maybe at some other interval). So for testing restart Thunderbird on each change you make.
  2. Ensure the shared mailboxes index can be written. You probably have it configured like
    plugin {
      acl_shared_dict = file:/var/lib/dovecot/db/shared-mailboxes.db
    }

    Check if such a file was created and is populated with new entries when you add ACLs from the mail client. As long as entries do not appear here, nothing can work.

  3. Enable debugging in the dovecot log or use the "debug" flag and check the ACLs for the user who should see a shared mailbox like this:
    doveadm acl debug -u [email protected] shared/users/box
    • Watch out for missing directories
    • Watch out for permission issues
    • Watch out for strangely created paths this could hint a misconfigured namespace prefix

PHP preg_replace() Examples

This post gives some simple examples for using regular expressions with preg_replace() in PHP scripts.

1. Syntax of preg_replace

While full syntax is

mixed preg_replace ( mixed $pattern , mixed 
$replacement , mixed $subject [, int $limit = -1 [, int &$count ]] )

2. Simple Replacing with preg_replace()

$result = preg_replace('/abc/', 'def', $string);   # Replace all 'abc' with 'def'
$result = preg_replace('/abc/i', 'def', $string);  # Replace with case insensitive matching
$result = preg_replace('/\s+/', '', $string);      # Strip all whitespaces

3. Advanced Usage of preg_replace()

Multiple replacements:

$result = preg_replace(
    array('/pattern1/', '/pattern2/'),
    array('replace1', 'replace2'),
    $string
);

Replacement Back References:

$result = preg_replace('/abc(def)hij/', '/\\1/', $string);
$result = preg_replace('/abc(def)hij/', '/$1/', $string);
$result = preg_replace('/abc(def)hij/', '/${1}/', $string);

Do only a finite number of replacements:

# Perform maximum of 5 replacements
$result = preg_replace('/abc/', 'def', $string, -1, 5);

Multi-line replacement

# Strip HTML tag
$result = preg_replace('#.*#m', '', $string);

Getting rid of Bash Ctrl+R

Today was a good day, as I stumbled over this post (at http://architects.dzone.com) hinting on the following bash key bindings:

bind '"\e[A":history-search-backward'
bind '"\e[B":history-search-forward'

It changes the behaviour of the up and down cursor keys to not go blindly through the history but only through items matching the current prompt. Of course at the disadvantage of having to clear the line to go through the full history. But as this can be achieved by a Ctrl-C at any time it is still preferrable to Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R Ctrl+R ....

How to Munin Graph JVM Memory Usage with Ubuntu tomcat

The following description works when using the Ubuntu "tomcat7" package:

Grab the "java/jstat__heap" plugin from munin-contrib @ github and place it into "/usr/share/munin/plugins/jstat__heap".

Link the plugin into /etc/munin/plugins

ln -s /usr/share/munin/plugins/jstat__heap /etc/munin/plugins/jstat_myname_heap

Choose some useful name instead of "myname". This allows to monitor multiple JVM setups.

Configure each link you created in for example a new plugin config file named "/etc/munin/plugin-conf.d/jstat" which should contain one section per JVM looking like this

[jstat_myname_heap]
user tomcat7
env.pidfilepath /var/run/tomcat7.pid
env.javahome /usr/

Sharing Screen With Multiple Users

How to detect screen sessions of other users:

screen -ls <user name>/

How to open screen to other users:

  1. Ctrl-A :multiuser on
  2. Ctrl-A :acladd <user to grant access>

Attach to other users screen session:

With session name

screen -x <user name>/<session name>

With PID and tty

screen -x <user name>/<pid>.<ptty>.<host>

How to dry-run with chef-client

The answer is simple: do not "dry-run", do "why-run"!

chef-client --why-run
chef-client -W

And the output looks nicer when using "-Fmin"

chef-client -Fmin -W

As with all other automation tools, the dry-run mode is not very predictive. Still it might indicate some of the things that will happen.

GTK Tray StatusIcon Example with PyGI

Here is an example on how to build a GtkStatusIcon using PyGI (Python GObject). The code actually implements a libpeas plugin that could be used with any GTK+ project that allows GI plugins. The tray icon could respond to left clicking by toggling the application window like many instant messengers do. On right clicks it presents a menu with the options to toggle the application window or quit the application.

from gi.repository import GObject, Peas, PeasGtk, Gtk

class TrayiconPlugin (GObject.Object, PeasActivatable):
    __gtype_name__ = 'TrayiconPlugin'

    object = GObject.property (type=GObject.Object)

    def do_activate (self):
        self.staticon = Gtk.StatusIcon ()
	self.staticon.set_from_stock (Gtk.STOCK_ABOUT)
        self.staticon.connect ("activate", self.trayicon_activate)
        self.staticon.connect ("popup_menu", self.trayicon_popup)
        self.staticon.set_visible (True)

    def trayicon_activate (self, widget, data = None):
        print "toggle app window!"

    def trayicon_quit (self, widget, data = None):
        print "quit app!"

    def trayicon_popup (self, widget, button, time, data = None):
        self.menu = Gtk.Menu ()

        menuitem_toggle = Gtk.MenuItem ("Show / Hide")
        menuitem_quit = Gtk.MenuItem ("Quit")

        menuitem_toggle.connect ("activate", self.trayicon_activate)
        menuitem_quit.connect ("activate", self.trayicon_quit)

        self.menu.append (menuitem_toggle)
        self.menu.append (menuitem_quit)

        self.menu.show_all ()
	self.menu.popup(None, None, lambda w,x: self.staticon.position_menu(self.menu, self.staticon), self.staticon, 3, time)

    def do_deactivate (self):
        self.staticon.set_visible (False)
        del self.staticon

Website Technology Crawl 12/2013

I've update the What Large Sites Use page with the results crawled in December 2013. Check it out to see who is using what! New column for HTML DOCTYPE was added. I'll soon post the followup on the changes compared to November.

Syndicate content