A few Ruby snippets for scripters

I do most of my automation and string manipulation scripting using Ruby. I know it’s not the most popular language these days, but it’s the one I know the best (thanks to my days of hacking on TextMate bundles) and it’s usually the fastest way for me to solve a problem. I have reams of snippets saved (and easily accessible with Snibbets) and thought I’d share a few that are useful for everyday scripting on macOS.

Scrub

Scrub uses the encode function to switch a string to UTF-16 discarding invalid characters (gremlins), then back to UTF-8. Applied as a String method, you can then use input.scrub to get clean text with all gremlins removed.

class ::String
  def scrub
    encode('utf-16', invalid: :replace).encode('utf-8')
  end

  def scrub!
    replace scrub
  end
end

Check for macOS

This can be modified or turned into a case statement to determine operating system. I often only need it to check if I can run Mac-only tools like pbcopy or not.

`uname`.strip == "Darwin"

Get macOS version

Just in case your script needs to behave differently across OS versions:

def macos_version
  begin
    `sw_vers`.strip.each_line do |line|
      if line.strip =~ /ProductVersion:\s+([\d.]+)$/
        return Regexp.last_match(1).to_f
      end
    end
    return 0
  rescue
    warn 'Failed to retrieve macOS version'
    Process.exit 1
  end
end

Rounding numbers

class ::Numeric
  # Round to nearest 5
  def round5
    ((self * 0.2).round / 0.2)
  end

  # Round to nearest 10
  def round10
    ((self * 0.1).round / 0.1)
  end
end

Human-readable file size

The #to_human method will convert 293592035 to “280MB”.

class Numeric
    def to_human
        units = %w{B KB MB GB TB}
        e = (Math.log(self)/Math.log(1024)).floor
        s = "%.1f" % (to_f / 1024**e)
        s.sub(/\.?0*$/, units[e])
    end
end

print File.size(File.expand_path(ARGV[0])).to_human

URL encoding

I used to use the CGI library for url encoding, but it doesn’t properly percent-encode spaces as %20, but rather as +, which breaks a lot of applications. The solution (as opposed to doing a manual search and replace) is to use the ERB library instead:

require 'erb'
ERB::Util.url_encode('string to encode')

Get a single keypress

For dialogs where you want to act as soon as a key is pressed without requiring pressing Return:

def get_keypress
    system "stty raw -echo"
    STDIN.getc
ensure
    system "stty -raw echo"
end
    
key = get_keypress.chr

Get the longest string in an array of strings

Of limited utility but I use it all the time when doing search algorithms:

class ::Array
  def longest_element
    group_by(&:size).max.last[0]
    # Leave off the [0] to get an array containing all of the longest elements when there's a tie
  end
end

p ['short', 'longest', 'longer'].longest_element
#=> "longest"

Symbolize hash keys

If you’re creating nested hash objects that end up with a mix of string and symbol keys, the easiest thing to do is symbolize all keys. #to_sym won’t do anything if the key is already a symbol.

class ::Hash
  # Turn all keys into symbols, including nested hashes
  def symbolize_keys
    each_with_object({}) { |(k, v), hsh| hsh[k.to_sym] = v.is_a?(Hash) ? v.symbolize_keys : v }
  end
end

# >> h = {'one' => 2, 'two' => { 'three' => 4 } }
# >> h.symbolize_keys
# {
#   :one => 2,
#   :two => {
#     :three => 4
#   }
# }

I hope that’s useful for aspiring Ruby scripters. If there’s interest, I can post (tons) more, but I also hope to get better about creating Gists that could be more easily searchable as a reference. The next step for Snibbets?

Bonus tip: Clipboard Preview

There’s a shell function I use frequently, easily replicable in any shell. It just shows you the contents of your clipboard (assuming text) without requiring a paste:

pbpaste | cat

In Fish that looks like:

# Defined in /Users/ttscoff/.config/fish/functions/cbp.fish @ line 1
function cbp --description 'ClipBoard Preview'
  pbpaste | cat
end

Like I said, useful in any shell as a way to ensure what you think is on your clipboard actually is. Just type cbp and get a preview before pasting anywhere.

ruby, scripting, shell