face recognizer

Play video files on localhost

Add subtitle to an MP4/MOV with FFMPEG

GObject(GTK3+) with Python on Mac

Install Mysql, Mariadb, Postgresql and Mongodb on Docker on Mac

Sort reverse by Unicode string length Raw

How variables are represented in memory

Convert PNG file to ICNS file on Mac

Install unbound dns cache on Mac

Install unbound dns cache on Mac

Clear Mac Finder and Dock icon cache, and Reset Launchpad layout

Clear Mac Finder and Dock icon cache

GCC 32bit compile on Mac

• The i386 architecture is deprecated for macOS
  

  $ gcc -m32 fib.c
  ld: warning: The i386 architecture is deprecated for macOS (remove from the Xcode build setting: ARCHS)
  ld: warning: ignoring file /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib/libSystem.tbd, missing required architecture i386 in file /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib/libSystem.tbd
  Undefined symbols for architecture i386:
    "_printf", referenced from:
        _main in fib-68f6b9.o
  ld: symbol(s) not found for architecture i386
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  

• Install i386 support
  

  $ sudo rm -rf /Library/Developer/CommandLineTools
  $ xcode-select --install
  $ open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg
  

• Compile
  

  $ gcc -m32 fib.c
  ld: warning: The i386 architecture is deprecated for macOS (remove from the Xcode build setting: ARCHS)
  

  $ make CFLAGS="-m32" fib
  cc -m32    fib.c   -o fib
  ld: warning: The i386 architecture is deprecated for macOS (remove from the Xcode build setting: ARCHS)
  

Paper Size in millimeter

Broken attachment filename with Apple mail

With Apple mail, Korean attachment filename is broken.

Attachment filename is encoded to UTF-8

Run the following command within Terminal, then restart Apple mail.

$ defaults write com.apple.mail NSPreferredMailCharset "UTF-8"

Rotate 7" touchscreen of Raspberry PI

• Add parameters to /boot/config.txt

  display_rotate=1
  dtoverlay=rpi-ft5406,touchscreen-swapped-x-y=1,touchscreen-inverted-x=1
  

• Parameters

  Rotate display
  
  display_rotate=0 # normal
  display_rotate=1 # rotate 90°
  display_rotate=2 # rotate 180°
  display_rotate=3 # rotate 270°
  

  Touchscreen
  
  touchscreen-size-x      Touchscreen X resolution, default 800
  touchscreen-size-y      Touchscreen Y resolution, default 600
  touchscreen-inverted-x  Invert touchscreen X coordinates, default 0
  touchscreen-inverted-y  Invert touchscreen Y coordinates, default 0
  touchscreen-swapped-x-y Swap X and Y coordinates, default 0
  

Language performance test

Lower value shows better performance

• C
  

  #include <stdio.h>
  
  int fib(int n) {
      if(n == 1) return 0;
      if(n == 2) return 1;
      return fib(n - 2) + fib(n - 1);
  }
  
  int main() {
      int i = 0;
      for(i = 1; i <= 40; i++) {
          printf("%d %d\n", i, fib(i));
      }
      printf("\nC\n");
      return 0;
  }
  

• Java
  

  public class Fib {
   
      public static int calc(int n) {
          if(n <= 1) return 0;
          if(n == 2) return 1;
          return Fib.calc(n - 2) + Fib.calc(n - 1);
      }
      public static void main(String[] args) {
          for(int i = 1; i <= 40; i++) {
              System.out.println(i + " " + Fib.calc(i));
          }
          System.out.println("\nJAVA");
      }
   
  }
  

• JavaScript
  

  #!/usr/bin/env node
  
  let range = Array.from({length: 40}, (x, i) => i+1);
  let fib = n => n === 1 ? 0 : n === 2 ? 1 : fib(n - 2) + fib(n - 1);
  
  range.forEach( i => console.log(i, fib(i)) );
  console.log("\nJavaScript");
  

• PHP
  

  #!/usr/bin/env php
  <?php
  function fib(int $n) {
      if ($n === 1) return 0;
      if ($n === 2) return 1;
      return fib($n - 2) + fib($n - 1);
  }
  
  foreach (range(1, 40) as $i) {
      echo $i, ' ', fib($i), PHP_EOL;
  }
  echo "\nPHP\n";
  

• Python
  

  #!/usr/bin/env python
  
  def fib(n):
    if n == 1:
      return 0
    elif n == 2:
      return 1
    return fib(n - 2) + fib(n - 1)
  
  if __name__ == "__main__":
    for i in range(1, 40 + 1):
      print(i, fib(i))
    print("\nPYTHON")
  

• Ruby
  

  #!/usr/bin/env ruby
  
  def fib(n)
    return 0 if n == 1
    return 1 if n == 2
    return fib(n - 2) + fib(n - 1)
  end
  
  (1..40).each do |i|
    puts "#{i.to_s} #{fib(i).to_s}"
  end
  puts "\nRUBY"
  

Allow SSH access based on Country using GeoIP

1. Install packages

   $ sudo apt install geoip-bin geoip-database
   

2. Create script

   $ sudo vi /usr/local/bin/sshfilter.sh
   

   
   #!/bin/bash
   
   ALLOWED_COUNTRIES="KR US GB NZ"
   ALLOWED_IP="192.168 127.0.0"
   
   [[ "`echo $1 | grep ':'`" != "" ]] && SUFFIX="6"
   if [[ $ALLOWED_IP =~ ${1:0:7} ]]; then
    logger -p authpriv.notice "SSH ALLOWED $1 LOCALDOMAIN"
    exit 0
   fi
   
   GEORESULT=`/usr/bin/geoiplookup${SUFFIX} "$1"`
   COUNTRY=`echo $GEORESULT | cut -d : -f 2 | xargs | head -1`
   COUNTRYCODE=`echo $COUNTRY | cut -d , -f 1 | xargs`
   [[ $ALLOWED_COUNTRIES =~ $COUNTRYCODE ]] && RESPONSE="ALLOWED" || RESPONSE="DENIED"
   logger -p authpriv.notice "SSH $RESPONSE $1 $COUNTRY"
   [[ $RESPONSE == "ALLOWED" ]] && exit 0 || exit 1
   

3. edit /etc/hosts.allow and /etc/hosts.deny

   # /etc/hosts.allow
   sshd: ALL: /usr/local/bin/sshfilter.sh %a
   

   # /etc/hosts.deny
   sshd: ALL
   

SSH lockout 60min after 5 brute force attempts in 10min

1. install fail2ban

   $ sudo apt update
   $ sudo apt install fail2ban
   

2. edit configuration

   $ sudo vi /etc/fail2ban/jail.conf
   

   [sshd]
   enabled  = true
   port     = ssh
   maxretry = 5    # 5 attempts not permitted
   findtime = 600  # within 10 minutes
   bantime  = 3600 # ban 1 hour
   logpath  = %(sshd_log)s
   backend  = %(sshd_backend)s
   

3. unban an ip address

   $ sudo fail2ban-client set sshd unbanip IP_ADDRESS
   

PIP upgrade all, python package

$ for package in `pip list --outdated | cut -d ' ' -f 1`
> do
> pip install --upgrade $package
> done

Serial port communication on Mac with SCREEN command

Use screen command to communicate with Serial port

1. Open Terminal or iTerm2
2. See if the serial port exists
   

   $ ls -l /dev/cu.*

   crw-rw-rw-  1 root  wheel   20,   1 Jun 10 21:07 /dev/cu.Bluetooth-Incoming-Port
   crw-rw-rw-  1 root  wheel   20,   3 Jun 12 18:13 /dev/cu.usbmodem1421401
   

3. Connect to the port

   $ screen -L /dev/cu.usbmodem1421401 115200

   -L : show log of the command from the serial port

4. Other commands

   # in a running session
   

   Ctrl-A, K : kill the session
   Ctrl-A, D : detach from the session
   

   # out of session
   

   $ screen -ls : list sessions
   
   There is a screen on:
   9244.ttys001.Dee15S (Attached)
   
   Format : [PID].[TTYID].[HOSTNAME]
   
   $ screen -r : attach the default session
   $ screen -r [NAME] : attach to a session named [NAME]
   $ screen -S [NAME] : attach to a session named [NAME]
   $ screen -d [ID] : detach from the session with screen id [ID]