Applications


WordPress: How to disable a plugin on all pages except for a specific one

A few days ago we were struggling to find a way to limit the amount of plugins that load at any point on a WordPress website. We noticed that several plugins enqueue their scripts and their styles in all requests to the website even if they are actually used on a single page only. This issue was important to address as it was making the whole server slower by giving it extra requests from the client that would never provide any actual benefit to the user.

Initially, we tried to selectively enable those plugins on their respective pages but we did not get it right and things would load out of order and break. Instead of following the ‘enable when needed‘ methodology we decided to follow the ‘disable unless needed‘ methodology which seemed simpler at the time.

Our changes involved in adding the following code in the functions.php file of our child theme.

//Register a filter at the correct event
add_filter( 'option_active_plugins', 'bf_plugin_control' );

function bf_plugin_control($plugins) {
  // If we are in the admin area do not touch anything
  if (is_admin()) {
    return $plugins;
  }
  
  // Check if we are at the expected page, if not remove the plugin from the active plugins list
  if(is_page("csv-to-kml-cell-site-map") === FALSE){ 
    // Finding the plugin in the active plugins list
    $key = array_search( 'csv-kml/index.php' , $plugins );
    if ( false !== $key ) {
      // Removing the plugin and dequeuing its scripts
      unset( $plugins[$key] );
      wp_dequeue_script( 'bf_csv_kml_script' );
    }
  }

  if(is_page("random-password-generator") === FALSE){ 
    $key = array_search( 'bytefreaks-password-generator/passwordGenerator.php' , $plugins );
    if ( false !== $key ) {
      unset( $plugins[$key] );
    }
  }
  
  if(is_page("xml-tree-visualizer") === FALSE){ 
    $key = array_search( 'xmltree/xml-tree.php' , $plugins );
    if ( false !== $key ) {
      unset( $plugins[$key] );
      wp_dequeue_script( 'bf_xml_namespace' );
      wp_dequeue_style( 'bf_xml_namespace' );
    }
  }

  return $plugins;
}

One day, we will clean the above code to make it tidy and reusable.. one day, that day is not today.

What the code above does is the following:

  • Using is_admin it checks if the Dashboard or the administration panel is attempting to be displayed, in that case it does not do any changes.
  • With is_page, it will additionally check if the parameter is for one of the pages specified and thus disable the plugin if the check fails.
  • PHP command array_search, will see if our plugin file is expected to be executed (all files in $plugins are the plugin files that are expected to be executed) .
  • wp_dequeue_script and wp_dequeue_style remove the previously enqueued scripts and styles of the plugin as long as you know the handles (or namespaces of the enqueued items).
    To get the handles (namespaces) we went through the plugin codes and found all instances of wp_enqueue_script and wp_enqueue_style.
    Please note that several small plugins do not have additional items in queue so no further action is needed.

Advertisements

Starting XAMPP with port 80 on Windows 10 Professional

Recently we were asked to have a look at a XAMPP installation on a Windows 10 Professional machine which would not start while giving the following error:

Problem detected!
Port 80 in use by "Unable to open process" with PID 4!
Apache WILL NOT start without the configured ports free!
You need to uninstall/disable/reconfigure the blocking application
or reconfigure Apache and the Control Panel to listen on a different port

The culprit of this problem was a module of the IIS (Internet Information Services for Windows Server) that is named World Wide Web Publishing Service (WWW service or W3SVC service). Apparently, the W3SVC was hoarding port 80 even though IIS was not executing. To provide a quick solution, we decided to stop the W3SVC and get over this difficulty in a jiffy.

As you can see in the following video, to stop the World Wide Web Publishing Service (WWW service or W3SVC service) we performed the next steps:

  1. Clicked on the Start button
  2. Typed in the word services, which showed the Services link which we clicked to start the windows services  manager
  3. Then, we scrolled down in the Services window until we found the World Wide Web Publishing Service
  4. Finally, we right clicked on it and selected Stop.

After that, XAMPP was able to start Apache on port 80 with no issues.

 


How to create a video from thousands of images using ffmpeg

We have this simulation that creates several frames demonstrating the life-cycle of an ant colony.
Having thousands of pictures is not very useful most of the times so we decided to create a video out of those frames.
To do so, we decided to use ffmpeg. The names of the files that we generate are 5 digit zero-leading auto increment numbers (e.g 00001.png and 00002.png) so we ended up with the following command:

ffmpeg -framerate 60 -i %05d.png video.mp4;


How to create a video from an audio file and an image using ffmpeg

Recently, we had this audio file ( mp3) that we wanted to upload to youtube.com. As it is known, youtube does not allow uploading audio files. Taking that into consideration we had to create a video with a static image just to upload the audio file to youtube. To do that, we used ffmpeg and the following command:

ffmpeg -loop 1 -i Saturday.png -i 20181020.mp3 -shortest -acodec copy 20181020.mp4;


How we concatenate multiple mp3 files into one using ffmpeg

Recently, we needed to concatenate multiple mp3 files into one. We had at our disposal a machine that had ffmpeg installed.
To perform the merge, we created a list (separated by the character |) of the mp3 files, in the order we wanted them merged and executed the concat operation of ffmpeg to complete our task. Our resulting command was the following

ffmpeg -i "concat:20181021_080743.MP3|20181021_090745.MP3|20181021_100745.MP3" -acodec copy 20181021.mp3


LibreOffice Calc: Get workbook path only

Get workbook path only

For Linux and Mac

=LEFT(
  CELL("filename"),
  FIND(
    CHAR(1),
    SUBSTITUTE(
      CELL("filename"),
      "/",
      CHAR(1),
      LEN(CELL("filename")) - LEN(
        SUBSTITUTE(
          CELL("filename"),
          "/",
          ""
        )
      )
    )
  ) -1
)&"'"

For Windows

=LEFT(
  CELL("filename"),
  FIND(
    CHAR(1),
    SUBSTITUTE(
      CELL("filename"),
      "\",
      CHAR(1),
      LEN(CELL("filename")) - LEN(
        SUBSTITUTE(
          CELL("filename"),
          "\",
          ""
        )
      )
    )
  ) -1
)&"'"

Bonus

If you want to remove the ' characters as well that are around the filename and path use the following  solution, this will allow you to create hyperlinks for the folders as well

=REPLACE(
  LEFT(
    CELL("filename"),
    FIND(CHAR(1),
      SUBSTITUTE(
        CELL("filename"),
        "/",
        CHAR(1),
        LEN(CELL("filename")) - LEN(
          SUBSTITUTE(
            CELL("filename"),
            "/",
            ""
          )
        )
      )
    ) -1
  )
  ,1,1,""
)

To create hyperlink as well, use the following

=HYPERLINK(
  REPLACE(
    LEFT(
      CELL("filename"),
      FIND(CHAR(1),
        SUBSTITUTE(
          CELL("filename"),
          "/",
          CHAR(1),
          LEN(CELL("filename")) - LEN(
            SUBSTITUTE(
              CELL("filename"),
              "/",
              ""
            )
          )
        )
      ) -1
    )
    ,1,1,""
  )
)

 

 


LibreOffice Calc: Get workbook full path with filename

Get workbook full path with filename

=LEFT(CELL("filename"),FIND("#",CELL("filename"))-1)

Explanation

If you want to get the workbook filename and path, you can do so with a formula that uses the LEFT and the FIND function.

The CELL("filename") function is used to get the full file name and path along with current sheet link:

The result will look like this:

'file:///home/user/path/documentName.ods'#$sheetName

Using the FIND function we find the position of the delimiter # and then using the LEFT function, we extract just the full directory path with the filename. We know the number of characters to extract by locating the the position of the hash # character with FIND and then subtracting 1 (to exclude itself as well).

Extra

If you want to remove the ' characters as well that are around the filename and path use the following solution

=REPLACE(
  LEFT(
    CELL("filename"),
    FIND(
      "#",
      CELL("filename")
    )-2
  ), 1, 1,""
)

 


LibreOffice Calc: Get workbook filename only

Get workbook filename only

For Linux and Mac

=TRIM(
  RIGHT(
    SUBSTITUTE(
      LEFT(
        CELL("filename"),
        FIND("#", CELL("filename")) -2
      ),
      "/",
      REPT(" ", LEN(CELL("filename")))
    ),
  LEN(CELL("filename"))
  )
)

For Windows

=TRIM(
  RIGHT(
    SUBSTITUTE(
      LEFT(
        CELL("filename"),
        FIND("#", CELL("filename")) -2
      ),
      "\",
      REPT(" ", LEN(CELL("filename")))
    ),
  LEN(CELL("filename"))
  )
)

The only change is changing the delimiter from / to \.


Horrible Solution: How to delete all docker logs

Recently, we needed to delete the logs of a running docker setup. To do so, we used the following horrible solution:

First, we executed docker system info | grep "Docker Root Dir";to get the installation path of docker. It resulted to the following:

Docker Root Dir: /var/lib/docker

Then, we truncated all log files using the following command while executing as root:

truncate -s 0 /var/lib/docker/containers/*/*-json.log;

Bonus

To make the command a onliner, use the following:

sudo sh -c 'truncate -s 0 $(docker system info | grep "Docker Root Dir" | cut -d ":" -f2 | cut -d " " -f2-)/containers/*/*-json.log';