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  • Creating a Beep from a Command Line or Shell Script
    02/03/2014 5:51PM

    If you have a long-running command on shell-script that you want to generate a beep upon completion on your PC running Linux do the following:

    . Make sure that the pcspkr module is loaded:

    # modprobe pcspkr

    . Then create a wrapper shell script that looks something like this:

    #!/bin/bash

    # Some long running command here . . .

    echo -e '\a' > /dev/console


  • Eclipse Crashing with SIGSEGV, Problematic Frame libgdk and/or libsoup Problem Solved
    01/31/2014 9:49AM

    I'm setting up a new workstation under Fedora Core 20 and getting my dev environment set up.

    I had copied over my /opt dir from my old machine which included an older version of Eclipse (3.8.2) that I had been using.  That version wasn't behaving very well and I decided to go with the latest and greatest stable version (Kepler, 4.3.1).

    Unfortunately, Kepler was dumping core with the following error:

     A fatal error has been detected by the Java Runtime Environment:

      SIGSEGV (0xb) at pc=0x00000030f703d09a, pid=2450, tid=139984564643584

     JRE version: Java(TM) SE Runtime Environment (7.0_51-b13) (build 1.7.0_51-b13)
     Java VM: Java HotSpot(TM) 64-Bit Server VM (24.51-b03 mixed mode linux-amd64 compressed oops)
     Problematic frame:
     C  [libgdk-x11-2.0.so.0+0x3d09a]  g_param_spec_object+0x3d09a

     Core dump written. Default location: /home/rchapin/core or core.2450

    I realized that I had installed Acrobat Reader, and since I'm on a 64 bit architecture that included all of the i686 rpms and compatibility libs.  I thought that that for some reason there might be some confusion between which version of libgdk that was being used.  That wasn't it.  I tried a different JDK (Oracle vs OpenJDK), nope, that wasn't it either.

    Eventually, I tried deleting (actually moving aside) the .eclipse/ dir in my home dir and deleting all of the .classpath, .settings, and .project files and dirs in my workspace and then re-installing my Eclipse plugins for Kepler.

    Worked like a charm.

    What I think was happening was that some of the plugins for different versions of Eclipse were being pulled in at runtime and causing the Kepler binary to crash.


  • Excellent Example and Explanation on How to Inject Properties from an External Properties File from Outside of a WAR in a Spring Application
    01/29/2014 8:39PM

    I am doing some refactoring on a Spring MVC application, pulling out configuration data and login crentials from the spring.xml file.

    What I want to do is to consolodate sensitive data into external .properties files that can be read, at runtime by the app and not require recompiling the war to make changes.

    Thanks to Ben Northrop and Summa Technologies for such a clear, concise and well written article.

    The long and the short of it (copied from the aforementioned article) is to add the following to your spring.xml

    <bean id="propertyPlaceholderConfigurer"  
    class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> 
      <property name="locations"> 
        <list> 
          <value>classpath:database.properties</value> 
        </list> 
      </property> 
    </bean> 

    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"> 
      <property name="user" value="${db.user}"/> 
      <property name="password" value="${db.password}"/> 
      ... 
    </bean>

  • Disabling Window Snapping for Fedora Core 20 Under Xfce
    01/28/2014 11:50AM

    For me, window snapping is incredibly annoying.

    For FC 20 with the Xfce spin, there a couple of knobs to turn before it can be turned off completely:


    Applications Menu/Settings/Window Manager:

    Go to the Advanced tab and uncheck 'Snap windows to screen border' and 'Snap windows to other windows'


    Applications Menu/Settings/Window Manager Tweaks:

    Go to Accessibility tabUncheck the 'Use edge resistance instead of window snapping'

  • Executing Dynamically Generated SQL Queries in a Shell Script and Saving the Output to a Variable
    01/10/2014 10:19AM

    If you would like to, in a shell script, dynamically generate SQL queries for MySQL and save the output of those queries to a variable that you can then use in the script, here is an example:

    #!/bin/bash

    for i in `cat tables_list.txt`
    do

       # Build the query
       QUERY="SELECT count(*) FROM ${i}"

       # Run the query from the command-line and save the
       # output into the $ROW_COUNT variable
       ROW_COUNT=$(echo $QUERY | mysql -u${USER_NAME} -p${PASSWORD} -h ${HOST} -P ${PORT} --skip-column-names ${DBASE})

       # Do something with the var...
       echo -n -e "$ROW_COUNT\t" >> $OUT_FILE
       echo "$i" >> $OUT_FILE

    done;

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