Technical Tidbits

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}"

oenv = ENV.to_hash
begin
  %w{BUNDLE_GEMFILE RUBYOPT GEM_HOME GIT_DIR GIT_WORK_TREE BUNDLE_BIN_PATH}.each { |key| ENV.delete(key) }
  output = IO.popen("xlshell "#{filename}" "#{worksheet}"")
  return output.readlines.collect { |f| f.strip }
ensure
  ENV.replace(oenv)
end

dscacheutil -flushcache

On newer Macs, somethings this works too.

sudo killall -HUP mDNSResponder

ssh-keygen -t rsa

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

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

Remove all old sessions, and then optimize the table.</p>

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

optimize TABLE sessions;

Should only be done on a dev machine:

rabbitmqctl stop_app
rabbitmqctl reset
rabbitmqctl start_app

A longer discussion at ewal.net

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

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

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 }'

# 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

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

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

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

git reset --soft HEAD^

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

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

When running CHEF, it needs root access, so if you are using something like chef-solo, and you like automated scripts, then here is how grant that access. PLEASE NOTE, THIS IS VERY UNSAFE, to avoid try, I created a (now obsolete) CHEF BOOTSTRAP.

$ mkdir -p /root/.ssh
$ chmod 700 /root/.ssh
$ chmod 600 /roiot/.ssh/authorized_keys
$ restorecon -R -v /root/.ssh

Bug with current version that will cause the process to not exit properly:</p>

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

Ticket was described here, but now the site (and history) have for wkhtmltopdf.org have moved. Thank you to wearepandr

# 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] <defunct>
deployer  2710  2698  0  2012 ?        00:00:04 [unicorn_rails] <defunct>

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

$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 = 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;

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;

Removing access to mysql users

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

GRANT ALL PRIVILEGES ON DATABASE @DATABASE_NAME@ TO @NEW_USERNAME@;
GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA public TO @NEW_USERNAME@;

For example, changing from the 'postgres' user to the 'deployer' user.

GRANT ALL PRIVILEGES ON DATABASE my_app TO deployer;
GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA public TO deployer;

CREATE USER myuser  WITH ENCRYPTED PASSWORD 'ppp';
GRANT USAGE ON SCHEMA public to myuser;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO myuser;

GRANT CONNECT ON DATABASE mydb to myuser;
c mydb
GRANT USAGE ON SCHEMA public to myuser;
GRANT SELECT ON ALL SEQUENCES IN SCHEMA public TO myuser;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO myuser;

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

rake db:sessions:clear

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

find . -name '*.php.eex' -exec sh -c 'mv "$0" "${0%.php.eex}.eex"' {} ;
find . -name '*.php' -exec sh -c 'mv "$0" "${0%.php}.eex"' {} ;

If you receive warnings about should and either are not ready to change, or don't want to, here is how you can silence the warnings.

Using should from rspec-expectations' old :should syntax without explicitly enabling the syntax is deprecated. Use the new :expect syntax or explicitly enable :should instead.

Using stub from rspec-mocks' old :should syntax without explicitly enabling the syntax is deprecated. Use the new :expect syntax or explicitly enable :should instead.

RSpec.configure do |config|
  config.mock_with :rspec do |c|
    c.syntax = [:should, :expect]
  end
  config.expect_with :rspec do |c|
    c.syntax = [:should, :expect]
  end
end

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

Find which process is listening on a certain port

lsof -i :12345 # for port 12345