Install jq and youtube-dl

Get a list of the last 100 URLs:

curl https://api.twitch.tv/kraken/channels/${TWITCH_USER}/videos?broadcasts=true&limit=100 | 
  jq -r '.videos[].url' > past_broadcasts.txt

Save them locally:

youtube-dl -a past_broadcasts.txt -o "%(upload_date)s.%(title)s.%(id)s.%(ext)s"

Did it. youtube-dl is smart enough to avoid re-downloading videos it already has, so as long as you run this often enough (I do daily), you should avoid losing videos before they’re deleted.

Thanks jrayhawk for the API info.

1. Install Redis: https://www.digitalocean.com/community/tutorials/how-to-install-and-use-redis
2. Install Webdis
   
3. Start a minecraft server with computercraft. You will need to have the http API enabled, which is the default.
4. Put down a turtle I recommend a turtle with a crafting square and a pickaxe. I also recommend giving it a label. If you’re not trying the turtle replication challenge, either disable fuel or get a fair bit of starting fuel. Write down the computer’s id.
5. Put down a chunk loader, if you’re in a modpack that has them, or DON’T log out. Computers and turtles can’t operate unless the chunks are loaded. If you’re putting down a chunkloader, I surrounded them with bedrock for foolproofing.

6. Open the turtle and download the following script, changing “redis.example.com” to your own redis instance: pastebin get 8FjggG9w startup
   After you have the script saved as ‘startup’, run it or reboot the computer, and it should start listening for instructions.

   redis = "http://redis.example.com" 
   queue = "sshbot" .. os.getComputerID()
   return_queue = queue .. "_return"
   print("Remote webdis queues on icyego: " .. queue .. " and " .. return_queue)
   print("Receiving remote commands.")
   
   function exec(str)
     print("Running: " .. str)
     f = fs.open("tmp", "w")
     f.write(str)
     f.close()
     p = loadfile("tmp")
    status, err = pcall(function () p = loadfile("tmp"); return p() end)
     if status then
       status, ret = pcall(function() return textutils.serialize(err) end)
       if status then
         result = ret
       else
         result = ""
       end
     else
       result = "Error: " .. err
     end
     print(result)
     return result
   end
   
   print("Now receiving remote commands.")
   while true do
     handle = http.get(redis .. "/BRPOP/" .. queue .. "/5.txt")
     if (handle and handle.getResponseCode() == 200) then 
       str = handle.readAll()
       handle.close()
       str = string.sub(str, string.len(queue) + 1)
       result = exec(str)
       if string.find(result, "Error: ") then
         result2 = exec("return " .. str)
         if string.find(result2, "Error: ") then a=0 else result=result2 end
       end
       http.post(redis, "LPUSH/" .. return_queue .. "/" .. result)
     end
   end
   

7. On your local machine, save the following, again replacing “redis.example.com”:

   #!/bin/bash
   function send() {
     curl -s -X POST -d "LPUSH/sshbot${1}/${2}" "http://redis.example.com" >/dev/null
   
   }
   
   function get() {
     curl -s -X GET "http://redis.example.com/BRPOP/sshbot${1}_return/20.json" | jq .BRPOP[1]
   }
   
   if [ $# -ne 1 ]; then
     echo "Usage: rlwrap ./sshbot <COMPUTER_ID>"
     exit 1
   fi
   ID=$1
   
   while read LINE; do
     send ${ID} "$LINE"
     get ${ID}
   done
   

8. Run: rlwrap ./sshbot , where is the turtle’s ID. You should be able to send commands to the computer now.

1. Install packages talk, talkd, inetutils-inetd
2. Make sure users have set ‘mesg y’
3. ‘talk user@localhost’. Despite documentation, ‘talk user’ will not work.

So have you ever used a web printer and it was great?

…

Yeah, me neither. It’s probably possible on windows, but try to add more than one OS to the network and it’s horrible. And actually printing is a major pain in Linux anyway. Theoretically ‘lp’ and the like have no problem with remote printers, but I wanted something I understood. So today I’m going to post my setup I use instead.

I have a computer physically connected to the printer. Let’s call it ‘printserver’. On that server there is a folder, /printme, which is constantly monitored by inode. Any file added to that directory is printed.

Suppose I downloaded cutecats.pdf and I want to print it. Then I run:

scp cutecats.pdf printserver:/printme

And voila, the cute cats get printed.

Here’s the setup for the server:

1. Get the printer to work. This is the hard step.
2. Make a directory /printme. Add any missing users, add a new group called ‘print’ and add everyone who needs to print to that, etc.

3. Set up /printme to be a tmpfs with the sticky bit set. (So we don’t fill up the hard drive)

   /etc/fstab
   tmpfs           /printme        tmpfs   rw,nodev,nosuid,noexec,uid=nobody,gid=print,mode=1770,size=1G  0       0
   

4. Install incron and add this to the incrontab (of user ‘print’ or ‘sudo’):

   # incrontab -l
   /printme IN_CLOSE_WRITE,IN_MOVED_TO lp $@/$#
   

   Note that this will preserve files after they’re printed, because my server is low-volume enough I don’t need to care.

(From Stack Overflow)

1. 64 bit requirements for pre-made binaries:

   sudo dpkg --add-architecture i386
   sudo apt-get update
   sudo apt-get install libstdc++6:i386 libxml2:i386 zlib1g:i386 libpopt0:i386
   

2. Install CUPS

   sudo apt-get update
   sudo apt-get install cups
   

3. Download DriverGo to http://support-au.canon.com.au/contents/AU/EN/0100459602.html and download driver

   64e2d00f0c8764d4032687d29e88f06727d88825 Linux_CAPT_PrinterDriver_V270_uk_EN.tar.gz
   

4. Extract and enter extracted folder

   tar xf Linux_CAPT_PrinterDriver_V270_uk_EN.tar.gz
   cd Linux_CAPT_PrinterDriver_V270_uk_EN
   

5. Install the custom drivers and ccpd

   sudo dpkg -i 64-bit_Driver/Debian/*.deb
   

6. Add the printer to CUPS and ccpd

   sudo lpadmin -p CANON_LBP6000 -m CNCUPSLBP6018CAPTS.ppd -v ccp://localhost:59687
   sudo lpadmin -p CANON_LBP6000 -E
   
   sudo ccpdadmin -p CANON_LBP6000 -o /dev/usb/lp0
   

7. Set the default printer

   sudo lpoptions -d CANON_LBP6000
   

8. Set ccpd to start on boot

   sudo update-rc.d ccpd defaults
   

I decided I wanted to show (restricted) data views on the web in table form. Specifically, ‘stylish.db’ is a database provided by a chrome plugin. Here’s an example script, stylish.view, which displays the contents of that. It contains a comment saying which database it’s a query on, together with the query.

-- stylish.db
SELECT style, code, GROUP_CONCAT(section_meta.value) as 'website(s)' FROM
 (SELECT styles.name AS style,
 sections.code AS code,sections.id AS sections_id
 FROM styles INNER JOIN sections ON sections.style_id = styles.id)
LEFT JOIN section_meta
 ON section_meta.section_id = sections_id
GROUP BY style;

The cool part here is that none of this was specific to stylish. I can quickly throw together a .view file for any database and put it on the web.

I add put any databases in cgi-bin/db, and add view.cgi to cgi-bin:

#!/bin/bash
# view.cgi
echo "Content-type: text/html"
echo

QUERY_FILE="${PATH_TRANSLATED}"
DB_NAME=$(head -n1 "${QUERY_FILE}" | sed -e 's/--\s*//')
DB="/home/za3k/cgi-bin/db/${DB_NAME}"

echo "<html><head><title>Query on #{DB_NAME}</title><link rel="stylesheet" type="text/css" href="db.css"></head><body><table id=\"${DB_NAME}\">"
sqlite3 "$DB" -html -header <"${QUERY_FILE}"
echo "</table></body></html>"

I add this to apache’s `.htaccess`:

Action view /cgi-bin/view.cgi
AddHandler view .view

Previous work:

• Optar (OPTical ARchive), a 2-D barcode format (github)
• Paperback

I wanted (for fun) to see if I could get data stored in paper formats. I’d read the previous work, and people put a lot of thought into density, but not a lot of thought into ease of retreival. First off, acid-free paper lasts 500 years or so, which is plenty long enough compared to any environmental stresses (moisture, etc) I expect on any paper I have.

Optar gets a density of 200kB / A4 page. By default, it requires a 600dpi printer, and a 600+dpi scanner. It has 3-of-12 bit redundancy using Golay codes, and spaces out the bits in an okay fashion.

Paperback gets a (theoretical) density of 500kB / A4 page. It needs a 600dpi printer, and a ~900dpi scanner.  It has configurable redundancy using Reed-Solomon codes. It looks completely unusable in practice (alignment issues, aside from being Windows-only).

Okay, so I think these are all stupid, because you need some custom software to decode them, which in any case where you’re decoding data stored on paper you probably don’t have that. I want to use standard barcodes, even if they’re going to be lower density. Let’s look at our options. I’m going to skip linear barcodes (low-density) and color barcodes (printing in color is expensive).  Since we need space between symbols, we want to pick the biggest versions of each code we can. For one, whitespace around codes is going to dominate actual code density for layout efficiency, and larger symbols are usually more dense. For another thing, we want to scan as few symbols as possible if we’re doing them one at a time.

Aztec From 15×15 to 151×151 square pixels. 1914 bytes maximum. Configurable Reed-Solomon error correction.

Density: 11.9 pixels per byte

Data Matrix From 10×10 to 144×144 square pixels. 1555 bytes maximum. Large, non-configurable error correction.

Density: 13.3 pixels per byte

QR Code From 21×21 to 177×177 square pixels. 2,953 bytes maximum. Somewhat configurable Reed-Solomon error correction.

Density: 10.6 pixels per byte

PDF417 17 height by 90-583 width.  1100 bytes maximum. Configurable Reed-Solomon error correction. PDF417 is a stacked linear barcode, and can be scanned by much simpler scanners instead of cameras. It also has built in cross-symbol linking (MacroPDF417), meaning you can scan a sequence of codes before getting output–handy for getting software to automatically link all the codes on a page.

Density: 9.01 pixels per byte

QR codes and PDF417 look like our contenders. PDF417 turns out to not scan well (at all, but especially at large symbol sizes), so despite some nice features let’s pick QR codes. Back when I worked on a digital library I made a component to generate QR codes on the fly, and I know how to scan them on my phone and webcam already from that, so it would be pretty easy to use them.

What density can we get on a sheet of A4 paper (8.25 in × 11.00 in, or 7.75in x 10.50in with half-inch margins)? I trust optar’s estimate (600 dpi = 200 pixels per inch) for printed/scanned pages since they seemed to test things. A max-size QR code is 144×144 pixels, or 0.72 x 0.72 inches at maximum density. We can fit 10 x 14 = 140 QR codes with maximum density on the page, less if we want decent spacing. That’s 140 QR codes x (2,953 bytes per QR code) = 413420 bytes = 413K per page before error correction.

That’s totally comparable to the other approaches above, and you can read the results with off-the-shelf software.  Bam.

In a previous post I discussed how to backup android with rsync. In this post, I’ll improve on that solution so it happens when you plug the phone in, rather than manually. My solution happens to know I have only one phone; you should adjust accordingly.

The process is

1. Plug the phone in
2. Unlock the screen (you’ll see a prompt to do this).
3. Backup starts automatically
4. Wait for the backup to finish before unplugging

First, let’s add a udev rule to auto-mount the phone when it’s plugged in and unlocked, and run appropriate scripts.

# 10-android.rules
ACTION=="add", SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="4ee2", MODE="0660", GROUP="plugdev", SYMLINK+="android", RUN+="/usr/local/bin/android-connected"
ACTION=="remove", SUBSYSTEM=="usb", ENV{ID_MODEL}=="Nexus_4", RUN+="/usr/local/bin/android-disconnected"

Next, we’ll add android-connected and android-disconnected

#!/bin/bash
# /usr/local/bin/android-connected
if [[ "$1" != "-f" ]]
then
 echo "/usr/local/bin/android-connected -f" | /usr/bin/at now
 exit 0
fi

sudo -u zachary DISPLAY=:0 /usr/bin/notify-send "Android plugged in, please unlock."
sudo -u zachary /usr/local/bin/android-mountfs
sudo -u zachary DISPLAY=:0 /usr/bin/notify-send "Mounted, backing up..."
/usr/bin/flock /var/lock/phone-backup.pid sudo -u zachary /usr/local/bin/phone-backup-xenu
sudo -u zachary DISPLAY=:0 /usr/bin/notify-send "Backup completed."

# !/bin/sh
# /usr/local/bin/android-disconnected
#!/bin/sh
sudo -u zachary DISPLAY=:0 /usr/bin/notify-send "Android unplugged."
sudo -u zachary /usr/local/bin/android-umountfs

We’ll add something to mount and unmount the system. Keeping in mind that mounting only works when the screen is unlocked we’ll put that in a loop that checks if the mount worked:

#!/bin/sh
# /usr/local/bin/android-mountfs

android_locked()
{
ls /media/android 2>/dev/null >/dev/null
[ "$?" -eq 2 ]
}

jmtpfs /media/android # mount
while android_locked; do
  fusermount -u /media/android
  sleep 3
  jmtpfs /media/android # mount
done

#!/bin/sh
# /usr/local/bin/android-umountfs
fusermount -u /media/android

The contents of  /usr/local/bin/phone-backup are pretty me-specific so I’ll omit it, but it copies /media/android over to a server. (fun detail: MTP doesn’t show all information even on a rooted phone, so there’s more work to do)

Most of the following taken from : http://www.msfn.org/board/topic/151992-install-xp-from-usb-without-extra-tools/, just modified to include syslinux support.

Let me know if there are any omissions; it an XP installer bluescreens on boot for me so I can’t actually test.

1. Obtain an XP iso file
2. Format drive with one FAT parition, marked bootable.

3. syslinux -i /dev/sdXX
   

4. $ cp /usr/lib/syslinux/bios/mbr.bin >/dev/sdX
   

5. $ mount /dev/sdXX /mnt
   

6. mkdir /tmp/xp_iso
   mount xp.iso /tmp/xp_iso
   cp -ar /tmp/xp_iso/* /mnt
   umount /tmp/xp_iso
   rmdir xp_iso
   

7. cp /usr/lib/syslinux/bios/{chain.c32,libutil.c32,menu.c32,libcom.c32} /mnt
   

8. cp /mnt/I386/{NTDETECT.COM,SETUPLDR.BIN,TXTSETUP.SIF} /mnt
   

9. Edit /mnt/syslinux.cfg:

   UI menu.c32# Windows XP
   LABEL windows_xp
   MENU LABEL Run Windows ^XP Setup
   COM32 chain.c32
   APPEND fs ntldr=SETUPLDR.BIN
   

10. umount /mnt
    

11. Boot from the USB stick

Just a quick shout-out to Chrome extension Stylish, which lets you add custom stylesheets to any web page. I’m using it with “display: none” and “visibility: hidden” exclusively, to hide annoying page elements.