Technical Tidbits

Deleting Git Branches

Delete the "demo_maintenance" branch on the "origin" remote server.

  git push origin :demo_maintenance # deletes the remote branch
  git branch -d demo_maintenance # deletes the local branch

If you need to 'force' the delete on your local machine, use -D

  git branch -D demo_maintenance # deletes the local branch

Checking Out New Git Branches

First locat the branches, then checkout the one you want (e.g. origin/demo1)

  git branch -r
  git checkout --track -b demo1 origin/demo1

Undo a local commit

If you committing a git change locally, you can undo it using the following command:

  git reset --soft HEAD^

Undo the last pushed commited

If you already committed the change, then you need to do hard resets:

  git reset --hard HEAD~1
  git push -f

Create a public / private key

  ssh-keygen -t dsa

Clear Your Local DNS Cache

  dscacheutil -flushcache

On newer Macs, somethings this works too.

  sudo killall -HUP mDNSResponder

Dealing with CSV files and MS Excel (.xls / .xlsx)

When dealing with CSV, you need to get your encodings correct.Excel will typically export to ISO-8859-1. This is not good, and should be converted to UTF-8 to support non english files.

To check the encoding of a file

  file -I original_file.csv

To convert between encodings (a few common examples)

  iconv --from-code=ISO-8859-1 --to-code=UTF-8 original_file.csv > new_file.utf8.csv
  iconv --from-code=MacRoman --to-code=UTF-8 original_file.csv > new_file.utf8.csv

When exporting files to be read within Excel, you will need to convert the CSV based on the target platform.

For MAC

  iconv --from-code=UTF-8 --to-code=MacRoman downloaded_file.csv > downloaded_file_mac.excel.csv 

For PC (untested)

  iconv --from-code=UTF-8 --to-code=Windows-1252 downloaded_file.csv > downloaded_file_windows.excel.csv

Run A Script Remotely Using SSH

For simple scripts, just pass them via a quoted string.

  ssh name@server.com 'ls -la'

For more complicated scripts, put them in a local file and stream them to the server.

  ssh name@server.com 'bash -s' < local_script.sh

Enable FTP on Mac OS X Lion

  # enable the ftp server
  sudo -s launchctl load -w /System/Library/LaunchDaemons/ftp.plist
  
  #disable the server when you are done
  sudo -s launchctl unload -w /System/Library/LaunchDaemons/ftp.plist

Find text in files within a directory

  grep -r "some words reward" /path/tp/look/*

Find large files on a Linux / Mac OS X machine

The following should owrk on your Mac OS X

  sudo find / -type f -size +20000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }'

For a linux (tested on Ubuntu), the $9 most liley needs to be an $8

  sudo find / -type f -size +20000k -exec ls -lh {} \; | awk '{ print $8 ": " $5 }'

Which Port is a Process Running On

Find which process is listening on a certain port

  lsof -i :12345 # for port 12345

Fixing Mount Issues When Upgrading to From Ubuntu 8.04

The following will get you SSH access back

mount -n -o remount,rw /
mkdir /var/run/network
/etc/init.d/networking restart
mkdir /dev/pts
mount /dev/pts
/etc/init.d/ssh restart

Next to start-up the services you care about

  sudo /etc/init.d/apache2 start
  sudo /etc/init.d/cron start
  sudo service mysql start

Destroy All RabbitMQ Queues

Should only be done on a dev machine:

  rabbitmqctl stop_app
  rabbitmqctl reset
  rabbitmqctl start_app

Tar / Untar a file

Compress a directly into a tar.gz file:

  tar cvzf myapp.tar.gz myapp/

Uncompress that file back into a directory:

  tar zxfv myapp.tar.gz

Uncompress a gz zip (no tar):

gzcat x.txt.gz >x.txt
gunzip -c x.txt.gz >x.txt

Clean / Clear / Delete Rails Databse Sessions

Don't forget to clear your sessions every once in a while

  rake db:sessions:clear

See how much memory something consumes in PHP

  $start_time = microtime(true);
  $start_memory = memory_get_usage();

  // INSERT CODE HERE

  $end_memory = memory_get_usage();
  $end_time = microtime(true);

  print_r(array(
    'memory (Mb)' => ($end_memory - $start_memory) / (1024 * 1024),
    'time (s)' => $end_time - $start_time
  ));

Memcache in PHP

  $memcache = new Memcache();
  $memcache->connect('localhost', 11211);

  function doSomethingSlow() {
    sleep(5);
    return "foobar";
  }

  $name = $memcache->get('name');
  if (!$name)
  {
    $name = doSomethingSlow();
    $memcache->set('name',$name);
  }
  
  echo $name;

  DELETE FROM sessions WHERE updated_at < DATE_SUB(NOW(), INTERVAL 1 DAY);
  optimize table sessions;

  require "yaml"
  File.open("./example.yml", 'w') {|f| f.write("
  workbook: 5
  sheet: 10
  header_index: 5
  headers: 
    - hello
    - hi
    - bye
  ") }
  data = YAML.load_file("./example.yml")
  puts "OLD DATA: #{data}"

  data["headers"] = [ "Hello", "Hi", "Bye" ]
  File.open("./example.yml", 'w') {|f| f.write(data.to_yaml) }

  data = YAML.load_file("./example.yml")
  puts "NEW DATA: #{data}"

  mysql -u myname -pmypassword -D mydb -e "show tables"

  SHOW GRANTS FOR deployer 
  # ALL ACCESS
  GRANT ALL ON myshop.* TO 'deployer'@'%' IDENTIFIED BY 'pass' ;
  # SELECT ONLY, and filtered by IP
  GRANT SELECT ON myshop.* TO deployer@'192.168.1.%' IDENTIFIED BY 'pass';
  # Or by domain name
  GRANT SELECT ON myshop.* TO deployer@'webapp.myserver.com' IDENTIFIED BY 'pass';
  FLUSH PRIVILEGES;

  REVOKE ALL PRIVILEGES, GRANT OPTION FROM 'deployer'@'%';

  # Locate defunct processes
  ps -A | grep defunct

  # Get the parent ID (UID PID PPID ...)
  ps -ef | grep defunct | more

  # for example...
  deployer  2707  2698  0  2012 ?        00:00:03 [unicorn_rails] 
  deployer  2710  2698  0  2012 ?        00:00:04 [unicorn_rails] 

  # Kill the parent PID (PPID)
  kill -9 2698

  $ xattr myapp.zip
  com.apple.quarantine

  xattr -d com.apple.quarantine myapp.zip

  # Or, if you already extracted it
  xattr -rd com.apple.quarantine ./myapp  

  sudo pmset -a standbydelay 86400 # only standby after 24 hours

    brew uninstall wkhtmltopdf
    cd /usr/local/Library/Formula/
    git checkout 6e2d550 /usr/local/Library/Formula/wkhtmltopdf.rb
    brew install wkhtmltopdf
    wkhtmltopdf --version | grep 0.9.9