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  • Jay Versluis 10:01 am on April 13, 2015 Permalink | Reply  
    Categories: Announcements, Linux ( 7 )

    LAMP Stack for Humans – now available on Amazon 

    Lampstack-SoftcoverMy book LAMP Stack for Humans is now available on Amazon. It this 284 page guide I’ll walk you through the process of turning an old laptop into an always-on server. You can use it to run web applications in the comfort of your own home or office – no “cloud” required.

    Together we will configure the entire server: you will learn how to install CentOS, Apache, PHP and MySQL (or MariaDB) and WordPress. I will show you how you can reach your server from other computers on the network and how to create regular backups.

    Perfect for the Linux newbie and those who want to get started with web applications without spending money “in the cloud” (in my opinion THE WORST expression for describing remote computers).

    If you’re an avid reader of this site and have always wished that some instructions would be presented in a more cohesive form rather than in snippets, then LAMP Stack for Humans is perfect for you.

     

    Grab your free sample today, or read the entire book for free via Kindle Unlimited!

     

     
    • Falkon 2:28 am on October 21, 2015 Permalink | Reply

      Hi Jay
      I have a question regarding WP adding a Landing page for an existing site, meaning to add a new page which only displays a big logo in the start and be able to make that logo a roleover logo, and then the click would navigate a user to the main ( index page) if you will. i am new to WP and PHP wise I am still learning so I would not know how to add an extra page as the index page and the first index page turns say into a home.html. How would you do that? I trying to learn PHP and WP to what I work with in HTML & CSS and front end designs.
      Beforehand allow me to thank you for you time, help and assistance,

      Best Regards
      Falkon

      • Jay Versluis 2:55 pm on October 21, 2015 Permalink | Reply

        Hi Falkon, that’s a VERY off-topic question for this post…

        WordPress does have a way to display a static page as front page, instead of the default blog posts. You can change it like this:

        • for the blog, create a new page with a title (no content is necessary)
        • head over to Settings – Reading
        • under Front Page Displays, select your pages
        • hit Save and refresh the front page

        As for the roll-over image: insert an image into your static front page, then link that image to wherever you want (you can do that with Add Media from the page creation dialogue).

        Hope this helps!

  • Jay Versluis 12:11 pm on June 11, 2016 Permalink | Reply  
    Categories: PHP, WordPress ( 25 )

    How to set WordPress Categories depending on the Post Title 

    I was working on a project the other day that required to determine which category a new post would go into, depending on the post title. This was important because posts were automatically acquired without the web interface, and in this workflow there was no way to pick a category other than the default.

    In our case we wanted to use a post fix in the title to determine which category was to be picked: for example, if a post title would end with “_ONE”, it should end up in Category 1, and if it ends up with “_TWO” it would end up in Category 2.

    Thankfully there’s a hook called save_post that is called every time a post is updated. At this point we can check what the post title is, determine the post fix, and set the correct category. Here’s a function that does just that:

    function set_my_categories($post_ID) {
    	
    	// grab the current title
    	$title = get_the_title($post_ID);
    	
    	// set the category depending on the last four characters of the title
    	// _ONE = Category 1
    	// _TWO = Category 2
    	$postfix = substr($title, -4);
    	if ($postfix == '_ONE') {
    		wp_set_post_categories($post_ID, array(1));
    	}
    	if ($postfix == '_TWO') {
    		wp_set_post_categories($post_ID, array(2));
    	}
    }
    add_action('save_post', 'set_my_categories');
    

    If a post fix is not present, the categories will not be changed.

    For this example I’m assuming that my categories are actually 1 and 2 on the system, something that’s not really the case. To determine the correct value set under wp_set_post_categories, I usually head over to Posts – Categories, select the category I want to use and check the URL of what WordPress gives me. Say the URL looks like this:

    http://domain.com/wp-admin/term.php?taxonomy=category&tag_ID=366&post_type=post

    then the tag_ID parameter hints that my category has an ID of 366, and that’s the value we need to use.

    And if a post needs to go into two categories, separate the category IDs with a comma like so:

    wp_set_post_categories($post_ID, array(2,3));

    Removing the post fix before the title is displayed

    Since our post fix is for internal purposes only, we may not want it to appear as part of the actual post title on the front page. But we also don’t want to remove it from every post once the category has been set and still have a reference in the admin interface. So the way to do it is to simply suppress it before out theme prints it out.

    The following code will do just that: if a post fix is present, curb the title. If not, leave the title unchanged.

    // curb title if we have a post fix
    $title = get_the_title();
    $postfix = substr($title, -4);
    if ($postfix == '_ONE' || $postfix == '_TWO') {
    	$title = substr($title, 0, -4);
    }
    // use echo $title to print the post title in your theme
    

    And there we have it. The same principle can be used if your title contains a certain keyword and you want to use it to add the post to a particular category automatically.

     
  • Jay Versluis 10:01 pm on April 2, 2016 Permalink | Reply
    Tags:   

    Categories: WordPress ( 133 )

    P2 Header Ad – Version 1.6 released 

    P2 Header Ad IconI’ve just released a new version of my P2 Header Ad plugin! It fixes a few issues I’ve come across in debug mode:

    • styles are now loaded via wp_enqueue_scripts hook
    • fixed a debug warning that assumed a constant rather than a value
    • verified compatibility with WordPress 4.5

    There’s still a lone warning that appears in WordPress 4.5 Debug Mode. It reads something like “get_currentuserinfo is deprecated since version 4.5! Use wp_get_current_user() instead”.

    This isn’t actually triggered by my plugin, but rather by the current version of P2 (1.5.8 and earlier). I’m sure the team will fix it very soon.

    As always, you can download the plugin from

     
  • Jay Versluis 12:57 pm on March 27, 2016 Permalink | Reply
    Tags: ,   

    Categories: Linux, Plesk ( 76 )

    How to fix “MLSD unable to build data connection” in ProFTP 

    Filezilla IconI’ve come across an odd problem today on a server that’s been working fine for all kinds of FTP traffic for many years. Turns out that today, FileZilla started complaining about explicit TLS connections (when available) and gave the following error message:

    425 MLSD unable to build data connection: operation not permitted

    Clients could still connect, but no directory content was displayed, nor was uploading new files possible. Rats, I thought. This was on a CentOS 6 server with Plesk 12 running without a hitch otherwise.

    Turns out that by default, ProFTP is configured to re-use TLS sessions – but it appears that this behaviour freaks out FileZilla, which in turn doesn’t like it and throws an error instead. This did not affect plain (non-secure) sessions.

    Thankfully, Adam Stohl knows the answer to this problem: tell ProFTP not to re-use TLS sessions. Open /etc/proftp.conf and add the following line to the bottom of the file:

    TLSOptions NoSessionReuseRequired

    The ProFTP service in Plesk is part of xinetd, so for those changes to take effect, simply restart it with this:

    service xinetd restart

    And voila, TLS connections can happen again. Thanks, Adam – you’re a life saver!

     

     
  • Jay Versluis 11:41 am on March 14, 2016 Permalink | Reply
    Tags: , Beta   

    Categories: Mac OS X ( 26 )

    How to switch off Developer Beta Downloads on Mac OS X 

    A while ago I thought it would be fun to run the OS X Developer Betas on my MacBook Pro. That was before El Captain was released. Once the buzz had died down I grew a little tired of the bi-weekly point release downloads that took about an hour to install.

    So how can we tell a Developer Beta Mac to become a “normal” non-beta Mac again?

    While forum posts suggest that it’s an impossible feat, it’s actually no trouble at all. Simply head over to System Preferences – App Store and find a button that reads “your computer is set to receive pre-release Software Update seeds”.

    mac-beta-versions

    Click it and an overlay window is shown, allowing you to “not show pre-release updates” anymore. Be warned however that when you do this, the option to bring up this dialogue disappears – so once switched off, there’s no going back easily (unless you install another beta from scratch, like you did when you first obtained yours).

    Note that when you switch this feature off, your Mac will remain on the beta you have currently installed, until a new release comes out and replaces it. This option will not remove beta files from your machine, nor will it turn your beta system into a non-beta system instantly: you’ll have to wait for the next release and use the regular update option for that.

    You can always check what’s currently installed by heading over to the Apple Icon and select About This Mac.

     
  • Jay Versluis 2:05 pm on January 16, 2016 Permalink | Reply
    Tags: Dolphin, Gamecube, Xbox Controller   

    Categories: Mac OS X ( 26 )

    How to connect your Xbox 360 Controller to Dolphin for Mac 

    DolphinI’ve been experimenting with the marvellous Dolphin Emulator recently. It’s an open source project that allows us to play Nintendo Gamecube and Wii games on modern hardware. Dolphin is available for Windows, OS X and Linux.

    I have a wireless Xbox 360 controller for Windows at my disposal, but the only Windows hardware I have is the first generation Surface Pro. While the controller connects without issues, the Surface sadly just isn’t fast enough to run Dolphin.

    My more powerful hardware is Mac based, and Dolphin runs great on my Mac Mini. But I had no idea how to connect my Xbox controller to it.

    Turns out it’s actually a breeze to setup: let me show you how it worked for me on OS X El Capitan.

    (More …)

     
  • Jay Versluis 5:16 pm on January 13, 2016 Permalink | Reply
    Tags: , ,   

    Categories: Commodore ( 24 )

    How to use direct block access commands in Commodore DOS 

    Commodore-Logo-PaddedWe can access each sector’s raw data on Commodore disk drives with direct block access commands. Supported drives include the 1541, 1571, the VICE emulator as well as the SD2IEC card reader (for the most part).

    Each single sided floppy contains 35 sectors, while a double sided 1571 formatted disk contains 70 sectors. Each track contains between 17 and 21 sectors depending on how far inside or outside they are. Each sector contains 255 bytes we can read or write.

    Sectors are the same as blocks: only the directory refers to them as “blocks” and shows us how many we have available.

    We’ll need to open two channels to our disk drives: a command channel and a data channel. Here’s how to do it:
    (More …)

     
  • Jay Versluis 9:17 am on January 2, 2016 Permalink | Reply
    Tags:   

    Categories: Commodore ( 24 )

    How to save data to your C128 RAM Expansion Unit (REU) 

    Commodore-Logo-PaddedWith a RAM Expansion Unit (REU), the Commodore 128 could address up to 512k of data. That was huge in the late eighties! All you needed was one of those REUs, plug it into your cartridge port, and so much more super fast memory was at your fingertips.

    But even with such a cartridge at hand, how do we actually make use of it from CBM BASIC 7.0? With three funky commands called STASH, FETCH and SWAP. Here’s how we can use them.

    The REUs cannot be addressed directly, like other memory in your computer. Instead, data has to be either copied from the C128 to the REU, or vice versa, or swapped out. All three commands take the same four parameters:

    • number of bytes to transfer
    • location in the C128 memory to start
    • REU bank (0-7, depending on the size of the REU)
    • location in the REU bank memory

    This sounds more cryptic than it actually is: the largest REU split 512k over 8 banks of 64k, so that the 8bit operating system could address it.

    So to store 200 bytes of C128 memory, starting at location 5000, saving it inside the REU’s bank 0, location 0, we can use the STASH command like so:

    STASH 200,3000,0,0
    

    To retrieve our data later and bring it back to the same C128 location as before, we can use FETCH with the same parameters:

    FETCH 200,3000,0,0
    

    Rather than copying, we can also exchange data in two places by literally swapping it over. Again the parameters are the same:

    SWAP 200,3000,0,0
    

    Enabling REUs in VICE

    Although I have a physical C128, I do not have a real REU. Maybe one day I’ll find one on eBay, but until then there’s an easy way to emulate an REU using VICE.

    To enable one, head over to Settings – Resource Inspector – Cartridges – REU. Pick the size you like, and even a hard disk location to make the contents of your REU survive restarts.

    Screen Shot 2016-01-02 at 09.08.35

    Screen Shot 2016-01-02 at 09.09.19

    Demo Listing

    Here’s a quick test that allows us to store an arbitrary message in memory, then stash or retrieve it from an attached REU.

    100 print "1 store message in internal memory"
    110 print "2 print message"
    120 print "3 stash message in reu"
    130 print "4 retrieve message from reu"
    140 print "5 clear internal memory"
    141 print "6 quit"
    150 input "your choice";m
    160 on m gosub 1010,1090,1210,1410,1310,2000
    170 run
    1000 :
    1010 rem input and save
    1020 input "what shall we store";a$
    1030 for i=1 to len(a$)
    1040 c$=mid$(a$,i,1)
    1050 poke 3000+i,asc(c$)
    1060 next
    1070 return
    1080 :
    1090 rem retrieve message
    1100 print:print "retrieving..."
    1110 for i=1 to 100
    1120 c=peek(3000+i)
    1130 b$=b$+chr$(c)
    1140 next
    1150 print b$
    1160 return
    1200 :
    1210 rem stash to reu
    1220 stash 200,3000,0,0
    1230 return
    1300 :
    1310 rem clear internal memory
    1320 for i=1 to 200
    1330 poke 3000+i,0
    1340 next
    1350 return
    1400 :
    1410 rem retrieve from reu
    1420 fetch 200,3000,0,0
    1430 return
    2000 :
    2010 rem the end
    2020 end
    

    We don’t see many BASIC listings these days anymore. Enjoy!

     
  • Jay Versluis 5:58 pm on December 27, 2015 Permalink | Reply
    Tags:   

    Categories: Commodore ( 24 )

    How to create relative data files on your Commodore 128 

    Commodore-Logo-PaddedThe CBM DOS can write “relative data” onto disk, based on individual records. The advantage is that all space is allocated once and then randomly accessed if and when it’s needed – much like the tracks on a CD.

    This approach is different from sequential files, which have to read or write the whole file in one go (Apple call this “reading and writing atomically”). So finding the 50th record in a sequential file can take some time, whereas retrieving record 50 from a relative file is just as fast as retrieving record 1 or record 157.

    Let’s see how we can deal with such relative files in CBM BASIC 7.0. This works with all physical disk drives (1541, 1571, etc) as well as the SD2IEC card reader – but not with your trusty old Datasette (for obvious reasons).

    This was revolutionary back in 1982!

    Creating Relative Files

    Here we create a new file with a REL extension using the DOPEN# keyword. When we do this for the first time, we need to tell the operating system how much data we’d like to allocate per record. Anything up to 255 bytes is fine. We’ll use 100 bytes in this example (the letter L followed by the length).

    10 dopen#1,"rel test",l100
    20 for i=1 to 100
    30 record#1,i
    40 a$="record"+str$(i)
    45 print "writing record ";i
    50 print#1,a$
    60 next
    70 close 1
    80 print "all done!"
    

    When we create a new file, CBM DOS doesn’t know how many records we’ll need, but it will create as many as necessary on the file. Here we create 100 entries using a for loop and write them to disk using the PRINT# statement.

    Notice that before saving a record, we must position the record pointer using RECORD#. That’s how our data is written to the correct position on disk. The whole loop will take a while to complete, but all space will be allocated on the disk as soon as we CLOSE the file.

    To add more records, we’ll simply position the record pointer to a later entry – even if one does not yet exist. CBM DOS will create the last record and all records leading up to it so they can be used later, up to a maximum of 65535 (space permitting obviously).

    Reading data from Relative Files

    Much like with sequential data, we can either use INPUT# or GET# to grab the data for an individual record. INPUT# reads everything until a CHR$(13) is found and works much faster, while GET# reads data one character at a time and is a lot slower.

    10 input"which record shall we retrieve";r$
    20 dopen#1,"rel test"
    30 record#1,val(r$)
    40 input#1,a$
    50 close 1
    60 print:print a$:print
    70 print"need another one? (y/n)"
    80 getkey k$:if k$="y" then goto 10:else end
    

    Here we ask the user which record we want to retrieve. Next we open our relative file using DOPEN#, position to the desired RECORD# and then read in its value using INPUT#. When we’re done we close the file and ask if the user wants to retrieve another record.

    While this type of data access is quick and convenient, it doesn’t help much unless you know which record is stored at which position. Think of an address book application: to find “Johnny Appleseed” can’t be done unless you sift through every single record until you find him.

    Commodore therefore suggest to use sequential files alongside relative files, in which things like a last name could be saved together with the record number. Likewise, another sequential file could hold all records for the first names, and appended accordingly when a new record is created, or replaced when updated.

     
  • Jay Versluis 5:36 pm on December 27, 2015 Permalink | Reply
    Tags:   

    Categories: Commodore ( 24 )

    How to create sequential files on your Commodore C128 

    Commodore-Logo-PaddedSequential files are files to which we can write arbitrary data and read it back later. We can even append data to the file later without having to re-write the whole file.

    This works with the Datasette (tape drive) as well as floppy drives. Here’s how to do it in CBM BASIC 7.0:

    Creating Sequential Files

    The C128 has a few special commands up its sleeve to aid us in this task. Here we create a new file using the DOPEN keyword and write 100 statements to it.

    10 dopen#1,"@seq test",w
    20 for i=1 to 100
    30 a$="record"+str$(i)
    40 print#1,a$
    50 print "writing ";a$
    60 next
    70 close 1
    

    We’re creating a new sequential file (SEQ extension rather than the usual PRG), using the w after the filename so that BASIC knows to create the file. The @ sign in front of the file name makes sure this file is overwritten every time we run the programme – omit it if you don’t want that functionality.

    Next we create a loop and generate a variable spelling RECORD 1, RECORD 2, etc. That’s your data. Each entry may be up to 127 characters in length (I believe) and is saved to the file by using the PRINT# keyword. Anything we could print to the screen, we can also print to a file.

    With each new PRINT# command, a carriage return is saved to disk. This can come in handy when we’re reading the data back in. If you need special characters to separate your data, feel free to use them.

    Appending data to Sequential Files

    If we need to add anything to the file (much like Linux would add to the end of a text file using the “greater than” symbol), we can use the APPEND# keyword:

    10 append#1,"seq test"
    20 for i=101 to 150
    30 a$="record"+str$(i)
    40 print#1,a$
    50 print "appending ";a$
    60 next
    70 close 1
    

    APPEND# opens the file for adding data and positions the pointer after the last entry in our file. We’ll do something very similar as above, creating records 101 to 150 and adding them to the file. Make sure to CLOSE the file so all data is saved to disk.

    Reading Sequential Data

    Much like PRINT# can be used to write data to disk, we can use INPUT# to read data back – almost equivalent to the INPUT keyword get get user input from a keyboard. The only difference is that out input comes from a different device:

    10 dopen#1,"seq test"
    20 for i=1 to 150
    30 input#1,a$
    40 print a$
    50 next
    60 close 1
    

    Here we open our file with DOPEN# and grab each entry in the file using the INPUT# keyword. This will automatically position the next INPUT# when a carriage return is received (CHR$(13)).

    This will work just fine as long as the original data does not contain any special characters, like a scary comma. If you need such characters, or if you want to ignore the carriage return, you can also use the GET# command to read one character at a time from disk. This is dramatically slower though.

    Notice that there’s no “end of file” marker as such: right now we need to know how many entries there are and read them accordingly. Reading beyond the data in our file will simply repeat the last record (on real devices) or crash your system (on VICE).

     
  • Jay Versluis 10:30 am on December 24, 2015 Permalink | Reply
    Tags:   

    Categories: Commodore ( 24 )

    How to switch the Commodore 1571 into 1541 mode and back 

    Commodore-Logo-PaddedThe Commodore 1571 floppy drive powers up in compatibility mode and behaves just like a 1541 drive – unless a C128 is connected and sends it a fast serial transfer.

    They did this because otherwise the drive wouldn’t be compatible with the C64 and Plus/4.

    The C128 speaks to its attached disk drive when we power it on, and that’s how a 1571 turns on its super fast magical properties. Holding down the Commodore key will boot into C64 mode, and the 1571 will in turn reset itself to 1541 emulation mode.

    Lucky for us, we can change this with a simple command, no matter what computer we’re using or which mode we’re currently in. This is done by first opening a command channel and then sending the 1571 the following switch command:

    // switch on 1571 mode
    OPEN 15,8,15,"U0>M1"
    CLOSE 15
    
    // switch on 1541 mode
    OPEN 15,8,15,"U0>M0"
    CLOSE 15
    

    This will let the 1571 behave like a 1571 even when attached to a C64 or Plus/4: format floppies on both sides and enjoy 1328 blocks without flipping disks. Sadly it won’t transfer data any faster because the attached computers just can’t handle it.

    Conversely, if we want to use a C128 and have our drive remain in 1541 mode for testing or compatibility, it works equally well.

    Rebooting your computer will reset this value. As far as I know, there is no way to test which mode the drive is in before issuing either of the above commands.

     
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