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Removing ANSI color codes from Rails logs

The colors in Rails log files are helpful when watching them but, since they are ANSI color codes like ^[[4;36;1m, can be annoying when you are reading the logs with a tool that does just prints those control characters (like less or vim).

Remove them with sed:

cat staging.log | sed -r "s/\x1B\[([0-9]{1,3}((;[0-9]{1,3})*)?)?[m|K]//g"

This will print the log without colors to your terminal. You can pipe the result into less for example.

To have a file you can vim around with, just write that output into a new file:

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Prevent the selenium webbrowser window from closing after a failed @javascript step

When cucumber encounters a failing step in a @javascript feature, the selenium browser window instantly closes. Sometimes you do not want that, because you need to see what is going on. You can click through the data your feature created, when you add the following file to your features/support directory:


After('@leave_the_window_open') do |scenario|
  if scenario.respond_to?(:status) && scenario.status == :failed
    print "Step Failed. Press return to close browser"

Use a Ruby method like a block or lambda

Sometimes you want to use a vanilla Ruby method like a block. You can use Object#method to obtain a method reference that responds to #call:

foo_plus = "foo".method(:+)"bar") # => "foobar"

The method reference also understands #to_proc so you can feed it to block-taking methods by prefixing it with &:

printer = method(:puts)
[1, 2, 3].each(&printer) # will print one line per number

Fix: "undefined method `bytesize' for #<Array>"

I believe that when WEBrick has trouble bringing up your Rails application, the WEBrick component that is supposed to print you a pretty error message has a bug and sometimes fails with this message:

"undefined method `bytesize' for #<Array>"

Starting the application in Passenger gave me a stacktrace in log/development.log that pointed to the actual problem.

Possible causes discovered by looking at the logs —————————————————–…

Convert the colorspace of a PDF from RGB to CMYK under Ubuntu Linux

Note that converting from RGB to CMYK will usually degrade your colors because no exact mapping is possible. Anyway, this Stackoverflow post worked for me:

-sColorConversionStrategy=CMYK -dProcessColorModel=/DeviceCMYK \
-sOutputFile=output.pdf input.pdf

Rotate a PDF under Ubuntu Linux

Use the PDF toolkit:

sudo apt-get install pdftk

To rotate page 1 by 90 degrees clockwise:

pdftk in.pdf cat 1E output out.pdf    # old pdftk
pdftk in.pdf cat 1east output out.pdf # new pdftk

To rotate all pages clockwise:

pdftk in.pdf cat 1-endE output out.pdf    # old pdftk
pdftk in.pdf cat 1-endeast output out.pdf # new pdftk

The E (old pdftk) or east (new pdftk) is meaningful if you want other rotations. From the man page:

The page rotation setting…

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Print large PDFs as a poster

Pdfposter is a Python script that allows to convert large PDFs into a PDF with multiple pages that can be printed and turned into one big poster.

In Ubuntu, you can install it with
sudo apt-get install pdfposter

Scaling to the desired size is a bit cumbersome. If you want to split large.pdf, I suggest you run
pdfposter -vns 0.5 large.pdf larger.poster.pdf
which will tell you into how many pages the file would be split. Then simply tweak the -s value till you get the desired number of pages, and remove the -n to generate the r…

Unpack a .tar.gz archive

You can unpack a .tar.gz file into the current directory like this:

tar -xzvf archive.tar.gz

The options used are

Process a file input
Be verbose, i.e. print each extracted file

Side notes:

  • The dash is optional (tar xzvf ... works as well).
  • For .tar.bz2 archives, use j instead of z (tar xjvf …`)
  • In order to create a *.tar.gz archive, use -c flag instead of -x flag.
  • The order of parameters matters.

Printing to PDF files on Ubuntu

This will install a printer called "PDF":

sudo apt-get install cups-pdf

Files will be put into ~/PDF/ without any questions asked.

Fix randomly failing PDF cucumber tests

Sometimes PDF cucumber tests fail at the first test run and succeed at the second run. You can fix this with this step:

When PDF generation is ready
And I follow "Save as PDF"
# Checks for PDF contents go here

Here is the step definition:

When /^PDF generation is ready$/ do
  Then 'I should see ""'
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Vector Magic: Precision Bitmap To Vector Conversion Online

Automatically convert bitmap images like JPEGs, GIFs and PNGs to the crisp, clean, scalable vector art of EPS, SVG, and PDF with the world's best auto-tracing software.

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Print-Friendly Images and Logos with CSS

The trick is this: send a low-resolution version of your image to the screen, and a high-resolution version to the printer.

Install LaTeX on Ubuntu 10.10

The Ubuntu Documentation on LaTeX says, that the packages tetex are no longer supported. You can install the alternative texlive (380 MB) via apt-get.

sudo apt-get install texlive
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PhantomJS: Headless WebKit with JavaScript API

PhantomJS is a minimalistic headless WebKit.

It has fast and native support for various web standards:

DOM handling, CSS selector, JSON, Canvas, and SVG.

PhantomJS can be fully scripted using JavaScript. It is an optimal solution for headless testing of web-based applications, site scraping, pages capture, SVG renderer, PDF converter and many other usages.

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Include existing PDF files into new TeX document

If you plan to insert an existing PDF into a new LaTeX document that you will compile to PDF, you can use \includegraphics for this. Although, be prepared to get tons of errors complaining about overfill hboxes and the like.
You can use this package that takes care:


In order to insert a PDF, use:


See the external link for more options.

Fix errors when rendering PDF output

If you run specs or your application and get an error like:
ActionController::MissingFile in 'ProductsController#show, should render PDF'
Cannot read file /some/file.pdf

You may be missing the HTMLDOC binary on your system. Install it like this on Debian/Ubuntu:
sudo apt-get install htmldoc

Test the content-type of a response in Cucumber

The step definitions below allow you to write this in both Webrat and Capybara:

When I follow "Download as PDF"
Then I should get a response with content-type "application/pdf"


Then /^I should get a response with content-type "([^"]*)"$/ do |content_type|
  page.response_headers['Content-Type'].should == content_type


Then /^I should get a response with content-type "([^"]*)"$/ do |content_type|
  response.content_type.should == content_type

Unfortunatly this do…

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The LaTeX Font Catalogue

Gallery of fonts you can use without much hassle in LaTeX. The license of the fonts vary, but are all free. Note that the fonts not necessarily are free to distribute, and some fonts are available for non-commercial use only.

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